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diff --git a/.venv/lib/python3.12/site-packages/numpy/core/tests/test_ufunc.py b/.venv/lib/python3.12/site-packages/numpy/core/tests/test_ufunc.py
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+import warnings
+import itertools
+import sys
+import ctypes as ct
+
+import pytest
+from pytest import param
+
+import numpy as np
+import numpy.core._umath_tests as umt
+import numpy.linalg._umath_linalg as uml
+import numpy.core._operand_flag_tests as opflag_tests
+import numpy.core._rational_tests as _rational_tests
+from numpy.testing import (
+    assert_, assert_equal, assert_raises, assert_array_equal,
+    assert_almost_equal, assert_array_almost_equal, assert_no_warnings,
+    assert_allclose, HAS_REFCOUNT, suppress_warnings, IS_WASM, IS_PYPY,
+    )
+from numpy.testing._private.utils import requires_memory
+from numpy.compat import pickle
+
+
+UNARY_UFUNCS = [obj for obj in np.core.umath.__dict__.values()
+                    if isinstance(obj, np.ufunc)]
+UNARY_OBJECT_UFUNCS = [uf for uf in UNARY_UFUNCS if "O->O" in uf.types]
+
+
+class TestUfuncKwargs:
+    def test_kwarg_exact(self):
+        assert_raises(TypeError, np.add, 1, 2, castingx='safe')
+        assert_raises(TypeError, np.add, 1, 2, dtypex=int)
+        assert_raises(TypeError, np.add, 1, 2, extobjx=[4096])
+        assert_raises(TypeError, np.add, 1, 2, outx=None)
+        assert_raises(TypeError, np.add, 1, 2, sigx='ii->i')
+        assert_raises(TypeError, np.add, 1, 2, signaturex='ii->i')
+        assert_raises(TypeError, np.add, 1, 2, subokx=False)
+        assert_raises(TypeError, np.add, 1, 2, wherex=[True])
+
+    def test_sig_signature(self):
+        assert_raises(TypeError, np.add, 1, 2, sig='ii->i',
+                      signature='ii->i')
+
+    def test_sig_dtype(self):
+        assert_raises(TypeError, np.add, 1, 2, sig='ii->i',
+                      dtype=int)
+        assert_raises(TypeError, np.add, 1, 2, signature='ii->i',
+                      dtype=int)
+
+    def test_extobj_refcount(self):
+        # Should not segfault with USE_DEBUG.
+        assert_raises(TypeError, np.add, 1, 2, extobj=[4096], parrot=True)
+
+
+class TestUfuncGenericLoops:
+    """Test generic loops.
+
+    The loops to be tested are:
+
+        PyUFunc_ff_f_As_dd_d
+        PyUFunc_ff_f
+        PyUFunc_dd_d
+        PyUFunc_gg_g
+        PyUFunc_FF_F_As_DD_D
+        PyUFunc_DD_D
+        PyUFunc_FF_F
+        PyUFunc_GG_G
+        PyUFunc_OO_O
+        PyUFunc_OO_O_method
+        PyUFunc_f_f_As_d_d
+        PyUFunc_d_d
+        PyUFunc_f_f
+        PyUFunc_g_g
+        PyUFunc_F_F_As_D_D
+        PyUFunc_F_F
+        PyUFunc_D_D
+        PyUFunc_G_G
+        PyUFunc_O_O
+        PyUFunc_O_O_method
+        PyUFunc_On_Om
+
+    Where:
+
+        f -- float
+        d -- double
+        g -- long double
+        F -- complex float
+        D -- complex double
+        G -- complex long double
+        O -- python object
+
+    It is difficult to assure that each of these loops is entered from the
+    Python level as the special cased loops are a moving target and the
+    corresponding types are architecture dependent. We probably need to
+    define C level testing ufuncs to get at them. For the time being, I've
+    just looked at the signatures registered in the build directory to find
+    relevant functions.
+
+    """
+    np_dtypes = [
+        (np.single, np.single), (np.single, np.double),
+        (np.csingle, np.csingle), (np.csingle, np.cdouble),
+        (np.double, np.double), (np.longdouble, np.longdouble),
+        (np.cdouble, np.cdouble), (np.clongdouble, np.clongdouble)]
+
+    @pytest.mark.parametrize('input_dtype,output_dtype', np_dtypes)
+    def test_unary_PyUFunc(self, input_dtype, output_dtype, f=np.exp, x=0, y=1):
+        xs = np.full(10, input_dtype(x), dtype=output_dtype)
+        ys = f(xs)[::2]
+        assert_allclose(ys, y)
+        assert_equal(ys.dtype, output_dtype)
+
+    def f2(x, y):
+        return x**y
+
+    @pytest.mark.parametrize('input_dtype,output_dtype', np_dtypes)
+    def test_binary_PyUFunc(self, input_dtype, output_dtype, f=f2, x=0, y=1):
+        xs = np.full(10, input_dtype(x), dtype=output_dtype)
+        ys = f(xs, xs)[::2]
+        assert_allclose(ys, y)
+        assert_equal(ys.dtype, output_dtype)
+
+    # class to use in testing object method loops
+    class foo:
+        def conjugate(self):
+            return np.bool_(1)
+
+        def logical_xor(self, obj):
+            return np.bool_(1)
+
+    def test_unary_PyUFunc_O_O(self):
+        x = np.ones(10, dtype=object)
+        assert_(np.all(np.abs(x) == 1))
+
+    def test_unary_PyUFunc_O_O_method_simple(self, foo=foo):
+        x = np.full(10, foo(), dtype=object)
+        assert_(np.all(np.conjugate(x) == True))
+
+    def test_binary_PyUFunc_OO_O(self):
+        x = np.ones(10, dtype=object)
+        assert_(np.all(np.add(x, x) == 2))
+
+    def test_binary_PyUFunc_OO_O_method(self, foo=foo):
+        x = np.full(10, foo(), dtype=object)
+        assert_(np.all(np.logical_xor(x, x)))
+
+    def test_binary_PyUFunc_On_Om_method(self, foo=foo):
+        x = np.full((10, 2, 3), foo(), dtype=object)
+        assert_(np.all(np.logical_xor(x, x)))
+
+    def test_python_complex_conjugate(self):
+        # The conjugate ufunc should fall back to calling the method:
+        arr = np.array([1+2j, 3-4j], dtype="O")
+        assert isinstance(arr[0], complex)
+        res = np.conjugate(arr)
+        assert res.dtype == np.dtype("O")
+        assert_array_equal(res, np.array([1-2j, 3+4j], dtype="O"))
+
+    @pytest.mark.parametrize("ufunc", UNARY_OBJECT_UFUNCS)
+    def test_unary_PyUFunc_O_O_method_full(self, ufunc):
+        """Compare the result of the object loop with non-object one"""
+        val = np.float64(np.pi/4)
+
+        class MyFloat(np.float64):
+            def __getattr__(self, attr):
+                try:
+                    return super().__getattr__(attr)
+                except AttributeError:
+                    return lambda: getattr(np.core.umath, attr)(val)
+
+        # Use 0-D arrays, to ensure the same element call
+        num_arr = np.array(val, dtype=np.float64)
+        obj_arr = np.array(MyFloat(val), dtype="O")
+
+        with np.errstate(all="raise"):
+            try:
+                res_num = ufunc(num_arr)
+            except Exception as exc:
+                with assert_raises(type(exc)):
+                    ufunc(obj_arr)
+            else:
+                res_obj = ufunc(obj_arr)
+                assert_array_almost_equal(res_num.astype("O"), res_obj)
+
+
+def _pickleable_module_global():
+    pass
+
+
+class TestUfunc:
+    def test_pickle(self):
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            assert_(pickle.loads(pickle.dumps(np.sin,
+                                              protocol=proto)) is np.sin)
+
+            # Check that ufunc not defined in the top level numpy namespace
+            # such as numpy.core._rational_tests.test_add can also be pickled
+            res = pickle.loads(pickle.dumps(_rational_tests.test_add,
+                                            protocol=proto))
+            assert_(res is _rational_tests.test_add)
+
+    def test_pickle_withstring(self):
+        astring = (b"cnumpy.core\n_ufunc_reconstruct\np0\n"
+                   b"(S'numpy.core.umath'\np1\nS'cos'\np2\ntp3\nRp4\n.")
+        assert_(pickle.loads(astring) is np.cos)
+
+    @pytest.mark.skipif(IS_PYPY, reason="'is' check does not work on PyPy")
+    def test_pickle_name_is_qualname(self):
+        # This tests that a simplification of our ufunc pickle code will
+        # lead to allowing qualnames as names.  Future ufuncs should
+        # possible add a specific qualname, or a hook into pickling instead
+        # (dask+numba may benefit).
+        _pickleable_module_global.ufunc = umt._pickleable_module_global_ufunc
+        obj = pickle.loads(pickle.dumps(_pickleable_module_global.ufunc))
+        assert obj is umt._pickleable_module_global_ufunc
+
+    def test_reduceat_shifting_sum(self):
+        L = 6
+        x = np.arange(L)
+        idx = np.array(list(zip(np.arange(L - 2), np.arange(L - 2) + 2))).ravel()
+        assert_array_equal(np.add.reduceat(x, idx)[::2], [1, 3, 5, 7])
+
+    def test_all_ufunc(self):
+        """Try to check presence and results of all ufuncs.
+
+        The list of ufuncs comes from generate_umath.py and is as follows:
+
+        =====  ====  =============  ===============  ========================
+        done   args   function        types                notes
+        =====  ====  =============  ===============  ========================
+        n      1     conjugate      nums + O
+        n      1     absolute       nums + O         complex -> real
+        n      1     negative       nums + O
+        n      1     sign           nums + O         -> int
+        n      1     invert         bool + ints + O  flts raise an error
+        n      1     degrees        real + M         cmplx raise an error
+        n      1     radians        real + M         cmplx raise an error
+        n      1     arccos         flts + M
+        n      1     arccosh        flts + M
+        n      1     arcsin         flts + M
+        n      1     arcsinh        flts + M
+        n      1     arctan         flts + M
+        n      1     arctanh        flts + M
+        n      1     cos            flts + M
+        n      1     sin            flts + M
+        n      1     tan            flts + M
+        n      1     cosh           flts + M
+        n      1     sinh           flts + M
+        n      1     tanh           flts + M
+        n      1     exp            flts + M
+        n      1     expm1          flts + M
+        n      1     log            flts + M
+        n      1     log10          flts + M
+        n      1     log1p          flts + M
+        n      1     sqrt           flts + M         real x < 0 raises error
+        n      1     ceil           real + M
+        n      1     trunc          real + M
+        n      1     floor          real + M
+        n      1     fabs           real + M
+        n      1     rint           flts + M
+        n      1     isnan          flts             -> bool
+        n      1     isinf          flts             -> bool
+        n      1     isfinite       flts             -> bool
+        n      1     signbit        real             -> bool
+        n      1     modf           real             -> (frac, int)
+        n      1     logical_not    bool + nums + M  -> bool
+        n      2     left_shift     ints + O         flts raise an error
+        n      2     right_shift    ints + O         flts raise an error
+        n      2     add            bool + nums + O  boolean + is ||
+        n      2     subtract       bool + nums + O  boolean - is ^
+        n      2     multiply       bool + nums + O  boolean * is &
+        n      2     divide         nums + O
+        n      2     floor_divide   nums + O
+        n      2     true_divide    nums + O         bBhH -> f, iIlLqQ -> d
+        n      2     fmod           nums + M
+        n      2     power          nums + O
+        n      2     greater        bool + nums + O  -> bool
+        n      2     greater_equal  bool + nums + O  -> bool
+        n      2     less           bool + nums + O  -> bool
+        n      2     less_equal     bool + nums + O  -> bool
+        n      2     equal          bool + nums + O  -> bool
+        n      2     not_equal      bool + nums + O  -> bool
+        n      2     logical_and    bool + nums + M  -> bool
+        n      2     logical_or     bool + nums + M  -> bool
+        n      2     logical_xor    bool + nums + M  -> bool
+        n      2     maximum        bool + nums + O
+        n      2     minimum        bool + nums + O
+        n      2     bitwise_and    bool + ints + O  flts raise an error
+        n      2     bitwise_or     bool + ints + O  flts raise an error
+        n      2     bitwise_xor    bool + ints + O  flts raise an error
+        n      2     arctan2        real + M
+        n      2     remainder      ints + real + O
+        n      2     hypot          real + M
+        =====  ====  =============  ===============  ========================
+
+        Types other than those listed will be accepted, but they are cast to
+        the smallest compatible type for which the function is defined. The
+        casting rules are:
+
+        bool -> int8 -> float32
+        ints -> double
+
+        """
+        pass
+
+    # from include/numpy/ufuncobject.h
+    size_inferred = 2
+    can_ignore = 4
+    def test_signature0(self):
+        # the arguments to test_signature are: nin, nout, core_signature
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(i),(i)->()")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1,  1,  0))
+        assert_equal(ixs, (0, 0))
+        assert_equal(flags, (self.size_inferred,))
+        assert_equal(sizes, (-1,))
+
+    def test_signature1(self):
+        # empty core signature; treat as plain ufunc (with trivial core)
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(),()->()")
+        assert_equal(enabled, 0)
+        assert_equal(num_dims, (0,  0,  0))
+        assert_equal(ixs, ())
+        assert_equal(flags, ())
+        assert_equal(sizes, ())
+
+    def test_signature2(self):
+        # more complicated names for variables
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(i1,i2),(J_1)->(_kAB)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (2, 1, 1))
+        assert_equal(ixs, (0, 1, 2, 3))
+        assert_equal(flags, (self.size_inferred,)*4)
+        assert_equal(sizes, (-1, -1, -1, -1))
+
+    def test_signature3(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(i1, i12),   (J_1)->(i12, i2)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (2, 1, 2))
+        assert_equal(ixs, (0, 1, 2, 1, 3))
+        assert_equal(flags, (self.size_inferred,)*4)
+        assert_equal(sizes, (-1, -1, -1, -1))
+
+    def test_signature4(self):
+        # matrix_multiply signature from _umath_tests
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(n,k),(k,m)->(n,m)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (2, 2, 2))
+        assert_equal(ixs, (0, 1, 1, 2, 0, 2))
+        assert_equal(flags, (self.size_inferred,)*3)
+        assert_equal(sizes, (-1, -1, -1))
+
+    def test_signature5(self):
+        # matmul signature from _umath_tests
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            2, 1, "(n?,k),(k,m?)->(n?,m?)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (2, 2, 2))
+        assert_equal(ixs, (0, 1, 1, 2, 0, 2))
+        assert_equal(flags, (self.size_inferred | self.can_ignore,
+                             self.size_inferred,
+                             self.size_inferred | self.can_ignore))
+        assert_equal(sizes, (-1, -1, -1))
+
+    def test_signature6(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            1, 1, "(3)->()")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1, 0))
+        assert_equal(ixs, (0,))
+        assert_equal(flags, (0,))
+        assert_equal(sizes, (3,))
+
+    def test_signature7(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            3, 1, "(3),(03,3),(n)->(9)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1, 2, 1, 1))
+        assert_equal(ixs, (0, 0, 0, 1, 2))
+        assert_equal(flags, (0, self.size_inferred, 0))
+        assert_equal(sizes, (3, -1, 9))
+
+    def test_signature8(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            3, 1, "(3?),(3?,3?),(n)->(9)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1, 2, 1, 1))
+        assert_equal(ixs, (0, 0, 0, 1, 2))
+        assert_equal(flags, (self.can_ignore, self.size_inferred, 0))
+        assert_equal(sizes, (3, -1, 9))
+
+    def test_signature9(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            1, 1, "(  3)  -> ( )")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1, 0))
+        assert_equal(ixs, (0,))
+        assert_equal(flags, (0,))
+        assert_equal(sizes, (3,))
+
+    def test_signature10(self):
+        enabled, num_dims, ixs, flags, sizes = umt.test_signature(
+            3, 1, "( 3? ) , (3? ,  3?) ,(n )-> ( 9)")
+        assert_equal(enabled, 1)
+        assert_equal(num_dims, (1, 2, 1, 1))
+        assert_equal(ixs, (0, 0, 0, 1, 2))
+        assert_equal(flags, (self.can_ignore, self.size_inferred, 0))
+        assert_equal(sizes, (3, -1, 9))
+
+    def test_signature_failure_extra_parenthesis(self):
+        with assert_raises(ValueError):
+            umt.test_signature(2, 1, "((i)),(i)->()")
+
+    def test_signature_failure_mismatching_parenthesis(self):
+        with assert_raises(ValueError):
+            umt.test_signature(2, 1, "(i),)i(->()")
+
+    def test_signature_failure_signature_missing_input_arg(self):
+        with assert_raises(ValueError):
+            umt.test_signature(2, 1, "(i),->()")
+
+    def test_signature_failure_signature_missing_output_arg(self):
+        with assert_raises(ValueError):
+            umt.test_signature(2, 2, "(i),(i)->()")
+
+    def test_get_signature(self):
+        assert_equal(umt.inner1d.signature, "(i),(i)->()")
+
+    def test_forced_sig(self):
+        a = 0.5*np.arange(3, dtype='f8')
+        assert_equal(np.add(a, 0.5), [0.5, 1, 1.5])
+        with pytest.warns(DeprecationWarning):
+            assert_equal(np.add(a, 0.5, sig='i', casting='unsafe'), [0, 0, 1])
+        assert_equal(np.add(a, 0.5, sig='ii->i', casting='unsafe'), [0, 0, 1])
+        with pytest.warns(DeprecationWarning):
+            assert_equal(np.add(a, 0.5, sig=('i4',), casting='unsafe'),
+                         [0, 0, 1])
+        assert_equal(np.add(a, 0.5, sig=('i4', 'i4', 'i4'),
+                                            casting='unsafe'), [0, 0, 1])
+
+        b = np.zeros((3,), dtype='f8')
+        np.add(a, 0.5, out=b)
+        assert_equal(b, [0.5, 1, 1.5])
+        b[:] = 0
+        with pytest.warns(DeprecationWarning):
+            np.add(a, 0.5, sig='i', out=b, casting='unsafe')
+        assert_equal(b, [0, 0, 1])
+        b[:] = 0
+        np.add(a, 0.5, sig='ii->i', out=b, casting='unsafe')
+        assert_equal(b, [0, 0, 1])
+        b[:] = 0
+        with pytest.warns(DeprecationWarning):
+            np.add(a, 0.5, sig=('i4',), out=b, casting='unsafe')
+        assert_equal(b, [0, 0, 1])
+        b[:] = 0
+        np.add(a, 0.5, sig=('i4', 'i4', 'i4'), out=b, casting='unsafe')
+        assert_equal(b, [0, 0, 1])
+
+    def test_signature_all_None(self):
+        # signature all None, is an acceptable alternative (since 1.21)
+        # to not providing a signature.
+        res1 = np.add([3], [4], sig=(None, None, None))
+        res2 = np.add([3], [4])
+        assert_array_equal(res1, res2)
+        res1 = np.maximum([3], [4], sig=(None, None, None))
+        res2 = np.maximum([3], [4])
+        assert_array_equal(res1, res2)
+
+        with pytest.raises(TypeError):
+            # special case, that would be deprecated anyway, so errors:
+            np.add(3, 4, signature=(None,))
+
+    def test_signature_dtype_type(self):
+        # Since that will be the normal behaviour (past NumPy 1.21)
+        # we do support the types already:
+        float_dtype = type(np.dtype(np.float64))
+        np.add(3, 4, signature=(float_dtype, float_dtype, None))
+
+    @pytest.mark.parametrize("get_kwarg", [
+            lambda dt: dict(dtype=x),
+            lambda dt: dict(signature=(x, None, None))])
+    def test_signature_dtype_instances_allowed(self, get_kwarg):
+        # We allow certain dtype instances when there is a clear singleton
+        # and the given one is equivalent; mainly for backcompat.
+        int64 = np.dtype("int64")
+        int64_2 = pickle.loads(pickle.dumps(int64))
+        # Relies on pickling behavior, if assert fails just remove test...
+        assert int64 is not int64_2
+
+        assert np.add(1, 2, **get_kwarg(int64_2)).dtype == int64
+        td = np.timedelta(2, "s")
+        assert np.add(td, td, **get_kwarg("m8")).dtype == "m8[s]"
+
+    @pytest.mark.parametrize("get_kwarg", [
+            param(lambda x: dict(dtype=x), id="dtype"),
+            param(lambda x: dict(signature=(x, None, None)), id="signature")])
+    def test_signature_dtype_instances_allowed(self, get_kwarg):
+        msg = "The `dtype` and `signature` arguments to ufuncs"
+
+        with pytest.raises(TypeError, match=msg):
+            np.add(3, 5, **get_kwarg(np.dtype("int64").newbyteorder()))
+        with pytest.raises(TypeError, match=msg):
+            np.add(3, 5, **get_kwarg(np.dtype("m8[ns]")))
+        with pytest.raises(TypeError, match=msg):
+            np.add(3, 5, **get_kwarg("m8[ns]"))
+
+    @pytest.mark.parametrize("casting", ["unsafe", "same_kind", "safe"])
+    def test_partial_signature_mismatch(self, casting):
+        # If the second argument matches already, no need to specify it:
+        res = np.ldexp(np.float32(1.), np.int_(2), dtype="d")
+        assert res.dtype == "d"
+        res = np.ldexp(np.float32(1.), np.int_(2), signature=(None, None, "d"))
+        assert res.dtype == "d"
+
+        # ldexp only has a loop for long input as second argument, overriding
+        # the output cannot help with that (no matter the casting)
+        with pytest.raises(TypeError):
+            np.ldexp(1., np.uint64(3), dtype="d")
+        with pytest.raises(TypeError):
+            np.ldexp(1., np.uint64(3), signature=(None, None, "d"))
+
+    def test_partial_signature_mismatch_with_cache(self):
+        with pytest.raises(TypeError):
+            np.add(np.float16(1), np.uint64(2), sig=("e", "d", None))
+        # Ensure e,d->None is in the dispatching cache (double loop)
+        np.add(np.float16(1), np.float64(2))
+        # The error must still be raised:
+        with pytest.raises(TypeError):
+            np.add(np.float16(1), np.uint64(2), sig=("e", "d", None))
+
+    def test_use_output_signature_for_all_arguments(self):
+        # Test that providing only `dtype=` or `signature=(None, None, dtype)`
+        # is sufficient if falling back to a homogeneous signature works.
+        # In this case, the `intp, intp -> intp` loop is chosen.
+        res = np.power(1.5, 2.8, dtype=np.intp, casting="unsafe")
+        assert res == 1  # the cast happens first.
+        res = np.power(1.5, 2.8, signature=(None, None, np.intp),
+                       casting="unsafe")
+        assert res == 1
+        with pytest.raises(TypeError):
+            # the unsafe casting would normally cause errors though:
+            np.power(1.5, 2.8, dtype=np.intp)
+
+    def test_signature_errors(self):
+        with pytest.raises(TypeError,
+                    match="the signature object to ufunc must be a string or"):
+            np.add(3, 4, signature=123.)  # neither a string nor a tuple
+
+        with pytest.raises(ValueError):
+            # bad symbols that do not translate to dtypes
+            np.add(3, 4, signature="%^->#")
+
+        with pytest.raises(ValueError):
+            np.add(3, 4, signature=b"ii-i")  # incomplete and byte string
+
+        with pytest.raises(ValueError):
+            np.add(3, 4, signature="ii>i")  # incomplete string
+
+        with pytest.raises(ValueError):
+            np.add(3, 4, signature=(None, "f8"))  # bad length
+
+        with pytest.raises(UnicodeDecodeError):
+            np.add(3, 4, signature=b"\xff\xff->i")
+
+    def test_forced_dtype_times(self):
+        # Signatures only set the type numbers (not the actual loop dtypes)
+        # so using `M` in a signature/dtype should generally work:
+        a = np.array(['2010-01-02', '1999-03-14', '1833-03'], dtype='>M8[D]')
+        np.maximum(a, a, dtype="M")
+        np.maximum.reduce(a, dtype="M")
+
+        arr = np.arange(10, dtype="m8[s]")
+        np.add(arr, arr, dtype="m")
+        np.maximum(arr, arr, dtype="m")
+
+    @pytest.mark.parametrize("ufunc", [np.add, np.sqrt])
+    def test_cast_safety(self, ufunc):
+        """Basic test for the safest casts, because ufuncs inner loops can
+        indicate a cast-safety as well (which is normally always "no").
+        """
+        def call_ufunc(arr, **kwargs):
+            return ufunc(*(arr,) * ufunc.nin, **kwargs)
+
+        arr = np.array([1., 2., 3.], dtype=np.float32)
+        arr_bs = arr.astype(arr.dtype.newbyteorder())
+        expected = call_ufunc(arr)
+        # Normally, a "no" cast:
+        res = call_ufunc(arr, casting="no")
+        assert_array_equal(expected, res)
+        # Byte-swapping is not allowed with "no" though:
+        with pytest.raises(TypeError):
+            call_ufunc(arr_bs, casting="no")
+
+        # But is allowed with "equiv":
+        res = call_ufunc(arr_bs, casting="equiv")
+        assert_array_equal(expected, res)
+
+        # Casting to float64 is safe, but not equiv:
+        with pytest.raises(TypeError):
+            call_ufunc(arr_bs, dtype=np.float64, casting="equiv")
+
+        # but it is safe cast:
+        res = call_ufunc(arr_bs, dtype=np.float64, casting="safe")
+        expected = call_ufunc(arr.astype(np.float64))  # upcast
+        assert_array_equal(expected, res)
+
+    def test_true_divide(self):
+        a = np.array(10)
+        b = np.array(20)
+        tgt = np.array(0.5)
+
+        for tc in 'bhilqBHILQefdgFDG':
+            dt = np.dtype(tc)
+            aa = a.astype(dt)
+            bb = b.astype(dt)
+
+            # Check result value and dtype.
+            for x, y in itertools.product([aa, -aa], [bb, -bb]):
+
+                # Check with no output type specified
+                if tc in 'FDG':
+                    tgt = complex(x)/complex(y)
+                else:
+                    tgt = float(x)/float(y)
+
+                res = np.true_divide(x, y)
+                rtol = max(np.finfo(res).resolution, 1e-15)
+                assert_allclose(res, tgt, rtol=rtol)
+
+                if tc in 'bhilqBHILQ':
+                    assert_(res.dtype.name == 'float64')
+                else:
+                    assert_(res.dtype.name == dt.name )
+
+                # Check with output type specified.  This also checks for the
+                # incorrect casts in issue gh-3484 because the unary '-' does
+                # not change types, even for unsigned types, Hence casts in the
+                # ufunc from signed to unsigned and vice versa will lead to
+                # errors in the values.
+                for tcout in 'bhilqBHILQ':
+                    dtout = np.dtype(tcout)
+                    assert_raises(TypeError, np.true_divide, x, y, dtype=dtout)
+
+                for tcout in 'efdg':
+                    dtout = np.dtype(tcout)
+                    if tc in 'FDG':
+                        # Casting complex to float is not allowed
+                        assert_raises(TypeError, np.true_divide, x, y, dtype=dtout)
+                    else:
+                        tgt = float(x)/float(y)
+                        rtol = max(np.finfo(dtout).resolution, 1e-15)
+                        # The value of tiny for double double is NaN
+                        with suppress_warnings() as sup:
+                            sup.filter(UserWarning)
+                            if not np.isnan(np.finfo(dtout).tiny):
+                                atol = max(np.finfo(dtout).tiny, 3e-308)
+                            else:
+                                atol = 3e-308
+                        # Some test values result in invalid for float16
+                        # and the cast to it may overflow to inf.
+                        with np.errstate(invalid='ignore', over='ignore'):
+                            res = np.true_divide(x, y, dtype=dtout)
+                        if not np.isfinite(res) and tcout == 'e':
+                            continue
+                        assert_allclose(res, tgt, rtol=rtol, atol=atol)
+                        assert_(res.dtype.name == dtout.name)
+
+                for tcout in 'FDG':
+                    dtout = np.dtype(tcout)
+                    tgt = complex(x)/complex(y)
+                    rtol = max(np.finfo(dtout).resolution, 1e-15)
+                    # The value of tiny for double double is NaN
+                    with suppress_warnings() as sup:
+                        sup.filter(UserWarning)
+                        if not np.isnan(np.finfo(dtout).tiny):
+                            atol = max(np.finfo(dtout).tiny, 3e-308)
+                        else:
+                            atol = 3e-308
+                    res = np.true_divide(x, y, dtype=dtout)
+                    if not np.isfinite(res):
+                        continue
+                    assert_allclose(res, tgt, rtol=rtol, atol=atol)
+                    assert_(res.dtype.name == dtout.name)
+
+        # Check booleans
+        a = np.ones((), dtype=np.bool_)
+        res = np.true_divide(a, a)
+        assert_(res == 1.0)
+        assert_(res.dtype.name == 'float64')
+        res = np.true_divide(~a, a)
+        assert_(res == 0.0)
+        assert_(res.dtype.name == 'float64')
+
+    def test_sum_stability(self):
+        a = np.ones(500, dtype=np.float32)
+        assert_almost_equal((a / 10.).sum() - a.size / 10., 0, 4)
+
+        a = np.ones(500, dtype=np.float64)
+        assert_almost_equal((a / 10.).sum() - a.size / 10., 0, 13)
+
+    @pytest.mark.skipif(IS_WASM, reason="fp errors don't work in wasm")
+    def test_sum(self):
+        for dt in (int, np.float16, np.float32, np.float64, np.longdouble):
+            for v in (0, 1, 2, 7, 8, 9, 15, 16, 19, 127,
+                      128, 1024, 1235):
+                # warning if sum overflows, which it does in float16
+                with warnings.catch_warnings(record=True) as w:
+                    warnings.simplefilter("always", RuntimeWarning)
+
+                    tgt = dt(v * (v + 1) / 2)
+                    overflow = not np.isfinite(tgt)
+                    assert_equal(len(w), 1 * overflow)
+
+                    d = np.arange(1, v + 1, dtype=dt)
+
+                    assert_almost_equal(np.sum(d), tgt)
+                    assert_equal(len(w), 2 * overflow)
+
+                    assert_almost_equal(np.sum(d[::-1]), tgt)
+                    assert_equal(len(w), 3 * overflow)
+
+            d = np.ones(500, dtype=dt)
+            assert_almost_equal(np.sum(d[::2]), 250.)
+            assert_almost_equal(np.sum(d[1::2]), 250.)
+            assert_almost_equal(np.sum(d[::3]), 167.)
+            assert_almost_equal(np.sum(d[1::3]), 167.)
+            assert_almost_equal(np.sum(d[::-2]), 250.)
+            assert_almost_equal(np.sum(d[-1::-2]), 250.)
+            assert_almost_equal(np.sum(d[::-3]), 167.)
+            assert_almost_equal(np.sum(d[-1::-3]), 167.)
+            # sum with first reduction entry != 0
+            d = np.ones((1,), dtype=dt)
+            d += d
+            assert_almost_equal(d, 2.)
+
+    def test_sum_complex(self):
+        for dt in (np.complex64, np.complex128, np.clongdouble):
+            for v in (0, 1, 2, 7, 8, 9, 15, 16, 19, 127,
+                      128, 1024, 1235):
+                tgt = dt(v * (v + 1) / 2) - dt((v * (v + 1) / 2) * 1j)
+                d = np.empty(v, dtype=dt)
+                d.real = np.arange(1, v + 1)
+                d.imag = -np.arange(1, v + 1)
+                assert_almost_equal(np.sum(d), tgt)
+                assert_almost_equal(np.sum(d[::-1]), tgt)
+
+            d = np.ones(500, dtype=dt) + 1j
+            assert_almost_equal(np.sum(d[::2]), 250. + 250j)
+            assert_almost_equal(np.sum(d[1::2]), 250. + 250j)
+            assert_almost_equal(np.sum(d[::3]), 167. + 167j)
+            assert_almost_equal(np.sum(d[1::3]), 167. + 167j)
+            assert_almost_equal(np.sum(d[::-2]), 250. + 250j)
+            assert_almost_equal(np.sum(d[-1::-2]), 250. + 250j)
+            assert_almost_equal(np.sum(d[::-3]), 167. + 167j)
+            assert_almost_equal(np.sum(d[-1::-3]), 167. + 167j)
+            # sum with first reduction entry != 0
+            d = np.ones((1,), dtype=dt) + 1j
+            d += d
+            assert_almost_equal(d, 2. + 2j)
+
+    def test_sum_initial(self):
+        # Integer, single axis
+        assert_equal(np.sum([3], initial=2), 5)
+
+        # Floating point
+        assert_almost_equal(np.sum([0.2], initial=0.1), 0.3)
+
+        # Multiple non-adjacent axes
+        assert_equal(np.sum(np.ones((2, 3, 5), dtype=np.int64), axis=(0, 2), initial=2),
+                     [12, 12, 12])
+
+    def test_sum_where(self):
+        # More extensive tests done in test_reduction_with_where.
+        assert_equal(np.sum([[1., 2.], [3., 4.]], where=[True, False]), 4.)
+        assert_equal(np.sum([[1., 2.], [3., 4.]], axis=0, initial=5.,
+                            where=[True, False]), [9., 5.])
+
+    def test_inner1d(self):
+        a = np.arange(6).reshape((2, 3))
+        assert_array_equal(umt.inner1d(a, a), np.sum(a*a, axis=-1))
+        a = np.arange(6)
+        assert_array_equal(umt.inner1d(a, a), np.sum(a*a))
+
+    def test_broadcast(self):
+        msg = "broadcast"
+        a = np.arange(4).reshape((2, 1, 2))
+        b = np.arange(4).reshape((1, 2, 2))
+        assert_array_equal(umt.inner1d(a, b), np.sum(a*b, axis=-1), err_msg=msg)
+        msg = "extend & broadcast loop dimensions"
+        b = np.arange(4).reshape((2, 2))
+        assert_array_equal(umt.inner1d(a, b), np.sum(a*b, axis=-1), err_msg=msg)
+        # Broadcast in core dimensions should fail
+        a = np.arange(8).reshape((4, 2))
+        b = np.arange(4).reshape((4, 1))
+        assert_raises(ValueError, umt.inner1d, a, b)
+        # Extend core dimensions should fail
+        a = np.arange(8).reshape((4, 2))
+        b = np.array(7)
+        assert_raises(ValueError, umt.inner1d, a, b)
+        # Broadcast should fail
+        a = np.arange(2).reshape((2, 1, 1))
+        b = np.arange(3).reshape((3, 1, 1))
+        assert_raises(ValueError, umt.inner1d, a, b)
+
+        # Writing to a broadcasted array with overlap should warn, gh-2705
+        a = np.arange(2)
+        b = np.arange(4).reshape((2, 2))
+        u, v = np.broadcast_arrays(a, b)
+        assert_equal(u.strides[0], 0)
+        x = u + v
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            u += v
+            assert_equal(len(w), 1)
+            assert_(x[0, 0] != u[0, 0])
+
+        # Output reduction should not be allowed.
+        # See gh-15139
+        a = np.arange(6).reshape(3, 2)
+        b = np.ones(2)
+        out = np.empty(())
+        assert_raises(ValueError, umt.inner1d, a, b, out)
+        out2 = np.empty(3)
+        c = umt.inner1d(a, b, out2)
+        assert_(c is out2)
+
+    def test_out_broadcasts(self):
+        # For ufuncs and gufuncs (not for reductions), we currently allow
+        # the output to cause broadcasting of the input arrays.
+        # both along dimensions with shape 1 and dimensions which do not
+        # exist at all in the inputs.
+        arr = np.arange(3).reshape(1, 3)
+        out = np.empty((5, 4, 3))
+        np.add(arr, arr, out=out)
+        assert (out == np.arange(3) * 2).all()
+
+        # The same holds for gufuncs (gh-16484)
+        umt.inner1d(arr, arr, out=out)
+        # the result would be just a scalar `5`, but is broadcast fully:
+        assert (out == 5).all()
+
+    @pytest.mark.parametrize(["arr", "out"], [
+                ([2], np.empty(())),
+                ([1, 2], np.empty(1)),
+                (np.ones((4, 3)), np.empty((4, 1)))],
+            ids=["(1,)->()", "(2,)->(1,)", "(4, 3)->(4, 1)"])
+    def test_out_broadcast_errors(self, arr, out):
+        # Output is (currently) allowed to broadcast inputs, but it cannot be
+        # smaller than the actual result.
+        with pytest.raises(ValueError, match="non-broadcastable"):
+            np.positive(arr, out=out)
+
+        with pytest.raises(ValueError, match="non-broadcastable"):
+            np.add(np.ones(()), arr, out=out)
+
+    def test_type_cast(self):
+        msg = "type cast"
+        a = np.arange(6, dtype='short').reshape((2, 3))
+        assert_array_equal(umt.inner1d(a, a), np.sum(a*a, axis=-1),
+                           err_msg=msg)
+        msg = "type cast on one argument"
+        a = np.arange(6).reshape((2, 3))
+        b = a + 0.1
+        assert_array_almost_equal(umt.inner1d(a, b), np.sum(a*b, axis=-1),
+                                  err_msg=msg)
+
+    def test_endian(self):
+        msg = "big endian"
+        a = np.arange(6, dtype='>i4').reshape((2, 3))
+        assert_array_equal(umt.inner1d(a, a), np.sum(a*a, axis=-1),
+                           err_msg=msg)
+        msg = "little endian"
+        a = np.arange(6, dtype='<i4').reshape((2, 3))
+        assert_array_equal(umt.inner1d(a, a), np.sum(a*a, axis=-1),
+                           err_msg=msg)
+
+        # Output should always be native-endian
+        Ba = np.arange(1, dtype='>f8')
+        La = np.arange(1, dtype='<f8')
+        assert_equal((Ba+Ba).dtype, np.dtype('f8'))
+        assert_equal((Ba+La).dtype, np.dtype('f8'))
+        assert_equal((La+Ba).dtype, np.dtype('f8'))
+        assert_equal((La+La).dtype, np.dtype('f8'))
+
+        assert_equal(np.absolute(La).dtype, np.dtype('f8'))
+        assert_equal(np.absolute(Ba).dtype, np.dtype('f8'))
+        assert_equal(np.negative(La).dtype, np.dtype('f8'))
+        assert_equal(np.negative(Ba).dtype, np.dtype('f8'))
+
+    def test_incontiguous_array(self):
+        msg = "incontiguous memory layout of array"
+        x = np.arange(64).reshape((2, 2, 2, 2, 2, 2))
+        a = x[:, 0,:, 0,:, 0]
+        b = x[:, 1,:, 1,:, 1]
+        a[0, 0, 0] = -1
+        msg2 = "make sure it references to the original array"
+        assert_equal(x[0, 0, 0, 0, 0, 0], -1, err_msg=msg2)
+        assert_array_equal(umt.inner1d(a, b), np.sum(a*b, axis=-1), err_msg=msg)
+        x = np.arange(24).reshape(2, 3, 4)
+        a = x.T
+        b = x.T
+        a[0, 0, 0] = -1
+        assert_equal(x[0, 0, 0], -1, err_msg=msg2)
+        assert_array_equal(umt.inner1d(a, b), np.sum(a*b, axis=-1), err_msg=msg)
+
+    def test_output_argument(self):
+        msg = "output argument"
+        a = np.arange(12).reshape((2, 3, 2))
+        b = np.arange(4).reshape((2, 1, 2)) + 1
+        c = np.zeros((2, 3), dtype='int')
+        umt.inner1d(a, b, c)
+        assert_array_equal(c, np.sum(a*b, axis=-1), err_msg=msg)
+        c[:] = -1
+        umt.inner1d(a, b, out=c)
+        assert_array_equal(c, np.sum(a*b, axis=-1), err_msg=msg)
+
+        msg = "output argument with type cast"
+        c = np.zeros((2, 3), dtype='int16')
+        umt.inner1d(a, b, c)
+        assert_array_equal(c, np.sum(a*b, axis=-1), err_msg=msg)
+        c[:] = -1
+        umt.inner1d(a, b, out=c)
+        assert_array_equal(c, np.sum(a*b, axis=-1), err_msg=msg)
+
+        msg = "output argument with incontiguous layout"
+        c = np.zeros((2, 3, 4), dtype='int16')
+        umt.inner1d(a, b, c[..., 0])
+        assert_array_equal(c[..., 0], np.sum(a*b, axis=-1), err_msg=msg)
+        c[:] = -1
+        umt.inner1d(a, b, out=c[..., 0])
+        assert_array_equal(c[..., 0], np.sum(a*b, axis=-1), err_msg=msg)
+
+    def test_axes_argument(self):
+        # inner1d signature: '(i),(i)->()'
+        inner1d = umt.inner1d
+        a = np.arange(27.).reshape((3, 3, 3))
+        b = np.arange(10., 19.).reshape((3, 1, 3))
+        # basic tests on inputs (outputs tested below with matrix_multiply).
+        c = inner1d(a, b)
+        assert_array_equal(c, (a * b).sum(-1))
+        # default
+        c = inner1d(a, b, axes=[(-1,), (-1,), ()])
+        assert_array_equal(c, (a * b).sum(-1))
+        # integers ok for single axis.
+        c = inner1d(a, b, axes=[-1, -1, ()])
+        assert_array_equal(c, (a * b).sum(-1))
+        # mix fine
+        c = inner1d(a, b, axes=[(-1,), -1, ()])
+        assert_array_equal(c, (a * b).sum(-1))
+        # can omit last axis.
+        c = inner1d(a, b, axes=[-1, -1])
+        assert_array_equal(c, (a * b).sum(-1))
+        # can pass in other types of integer (with __index__ protocol)
+        c = inner1d(a, b, axes=[np.int8(-1), np.array(-1, dtype=np.int32)])
+        assert_array_equal(c, (a * b).sum(-1))
+        # swap some axes
+        c = inner1d(a, b, axes=[0, 0])
+        assert_array_equal(c, (a * b).sum(0))
+        c = inner1d(a, b, axes=[0, 2])
+        assert_array_equal(c, (a.transpose(1, 2, 0) * b).sum(-1))
+        # Check errors for improperly constructed axes arguments.
+        # should have list.
+        assert_raises(TypeError, inner1d, a, b, axes=-1)
+        # needs enough elements
+        assert_raises(ValueError, inner1d, a, b, axes=[-1])
+        # should pass in indices.
+        assert_raises(TypeError, inner1d, a, b, axes=[-1.0, -1.0])
+        assert_raises(TypeError, inner1d, a, b, axes=[(-1.0,), -1])
+        assert_raises(TypeError, inner1d, a, b, axes=[None, 1])
+        # cannot pass an index unless there is only one dimension
+        # (output is wrong in this case)
+        assert_raises(np.AxisError, inner1d, a, b, axes=[-1, -1, -1])
+        # or pass in generally the wrong number of axes
+        assert_raises(np.AxisError, inner1d, a, b, axes=[-1, -1, (-1,)])
+        assert_raises(np.AxisError, inner1d, a, b, axes=[-1, (-2, -1), ()])
+        # axes need to have same length.
+        assert_raises(ValueError, inner1d, a, b, axes=[0, 1])
+
+        # matrix_multiply signature: '(m,n),(n,p)->(m,p)'
+        mm = umt.matrix_multiply
+        a = np.arange(12).reshape((2, 3, 2))
+        b = np.arange(8).reshape((2, 2, 2, 1)) + 1
+        # Sanity check.
+        c = mm(a, b)
+        assert_array_equal(c, np.matmul(a, b))
+        # Default axes.
+        c = mm(a, b, axes=[(-2, -1), (-2, -1), (-2, -1)])
+        assert_array_equal(c, np.matmul(a, b))
+        # Default with explicit axes.
+        c = mm(a, b, axes=[(1, 2), (2, 3), (2, 3)])
+        assert_array_equal(c, np.matmul(a, b))
+        # swap some axes.
+        c = mm(a, b, axes=[(0, -1), (1, 2), (-2, -1)])
+        assert_array_equal(c, np.matmul(a.transpose(1, 0, 2),
+                                        b.transpose(0, 3, 1, 2)))
+        # Default with output array.
+        c = np.empty((2, 2, 3, 1))
+        d = mm(a, b, out=c, axes=[(1, 2), (2, 3), (2, 3)])
+        assert_(c is d)
+        assert_array_equal(c, np.matmul(a, b))
+        # Transposed output array
+        c = np.empty((1, 2, 2, 3))
+        d = mm(a, b, out=c, axes=[(-2, -1), (-2, -1), (3, 0)])
+        assert_(c is d)
+        assert_array_equal(c, np.matmul(a, b).transpose(3, 0, 1, 2))
+        # Check errors for improperly constructed axes arguments.
+        # wrong argument
+        assert_raises(TypeError, mm, a, b, axis=1)
+        # axes should be list
+        assert_raises(TypeError, mm, a, b, axes=1)
+        assert_raises(TypeError, mm, a, b, axes=((-2, -1), (-2, -1), (-2, -1)))
+        # list needs to have right length
+        assert_raises(ValueError, mm, a, b, axes=[])
+        assert_raises(ValueError, mm, a, b, axes=[(-2, -1)])
+        # list should not contain None, or lists
+        assert_raises(TypeError, mm, a, b, axes=[None, None, None])
+        assert_raises(TypeError,
+                      mm, a, b, axes=[[-2, -1], [-2, -1], [-2, -1]])
+        assert_raises(TypeError,
+                      mm, a, b, axes=[(-2, -1), (-2, -1), [-2, -1]])
+        assert_raises(TypeError, mm, a, b, axes=[(-2, -1), (-2, -1), None])
+        # single integers are AxisErrors if more are required
+        assert_raises(np.AxisError, mm, a, b, axes=[-1, -1, -1])
+        assert_raises(np.AxisError, mm, a, b, axes=[(-2, -1), (-2, -1), -1])
+        # tuples should not have duplicated values
+        assert_raises(ValueError, mm, a, b, axes=[(-2, -1), (-2, -1), (-2, -2)])
+        # arrays should have enough axes.
+        z = np.zeros((2, 2))
+        assert_raises(ValueError, mm, z, z[0])
+        assert_raises(ValueError, mm, z, z, out=z[:, 0])
+        assert_raises(ValueError, mm, z[1], z, axes=[0, 1])
+        assert_raises(ValueError, mm, z, z, out=z[0], axes=[0, 1])
+        # Regular ufuncs should not accept axes.
+        assert_raises(TypeError, np.add, 1., 1., axes=[0])
+        # should be able to deal with bad unrelated kwargs.
+        assert_raises(TypeError, mm, z, z, axes=[0, 1], parrot=True)
+
+    def test_axis_argument(self):
+        # inner1d signature: '(i),(i)->()'
+        inner1d = umt.inner1d
+        a = np.arange(27.).reshape((3, 3, 3))
+        b = np.arange(10., 19.).reshape((3, 1, 3))
+        c = inner1d(a, b)
+        assert_array_equal(c, (a * b).sum(-1))
+        c = inner1d(a, b, axis=-1)
+        assert_array_equal(c, (a * b).sum(-1))
+        out = np.zeros_like(c)
+        d = inner1d(a, b, axis=-1, out=out)
+        assert_(d is out)
+        assert_array_equal(d, c)
+        c = inner1d(a, b, axis=0)
+        assert_array_equal(c, (a * b).sum(0))
+        # Sanity checks on innerwt and cumsum.
+        a = np.arange(6).reshape((2, 3))
+        b = np.arange(10, 16).reshape((2, 3))
+        w = np.arange(20, 26).reshape((2, 3))
+        assert_array_equal(umt.innerwt(a, b, w, axis=0),
+                           np.sum(a * b * w, axis=0))
+        assert_array_equal(umt.cumsum(a, axis=0), np.cumsum(a, axis=0))
+        assert_array_equal(umt.cumsum(a, axis=-1), np.cumsum(a, axis=-1))
+        out = np.empty_like(a)
+        b = umt.cumsum(a, out=out, axis=0)
+        assert_(out is b)
+        assert_array_equal(b, np.cumsum(a, axis=0))
+        b = umt.cumsum(a, out=out, axis=1)
+        assert_(out is b)
+        assert_array_equal(b, np.cumsum(a, axis=-1))
+        # Check errors.
+        # Cannot pass in both axis and axes.
+        assert_raises(TypeError, inner1d, a, b, axis=0, axes=[0, 0])
+        # Not an integer.
+        assert_raises(TypeError, inner1d, a, b, axis=[0])
+        # more than 1 core dimensions.
+        mm = umt.matrix_multiply
+        assert_raises(TypeError, mm, a, b, axis=1)
+        # Output wrong size in axis.
+        out = np.empty((1, 2, 3), dtype=a.dtype)
+        assert_raises(ValueError, umt.cumsum, a, out=out, axis=0)
+        # Regular ufuncs should not accept axis.
+        assert_raises(TypeError, np.add, 1., 1., axis=0)
+
+    def test_keepdims_argument(self):
+        # inner1d signature: '(i),(i)->()'
+        inner1d = umt.inner1d
+        a = np.arange(27.).reshape((3, 3, 3))
+        b = np.arange(10., 19.).reshape((3, 1, 3))
+        c = inner1d(a, b)
+        assert_array_equal(c, (a * b).sum(-1))
+        c = inner1d(a, b, keepdims=False)
+        assert_array_equal(c, (a * b).sum(-1))
+        c = inner1d(a, b, keepdims=True)
+        assert_array_equal(c, (a * b).sum(-1, keepdims=True))
+        out = np.zeros_like(c)
+        d = inner1d(a, b, keepdims=True, out=out)
+        assert_(d is out)
+        assert_array_equal(d, c)
+        # Now combined with axis and axes.
+        c = inner1d(a, b, axis=-1, keepdims=False)
+        assert_array_equal(c, (a * b).sum(-1, keepdims=False))
+        c = inner1d(a, b, axis=-1, keepdims=True)
+        assert_array_equal(c, (a * b).sum(-1, keepdims=True))
+        c = inner1d(a, b, axis=0, keepdims=False)
+        assert_array_equal(c, (a * b).sum(0, keepdims=False))
+        c = inner1d(a, b, axis=0, keepdims=True)
+        assert_array_equal(c, (a * b).sum(0, keepdims=True))
+        c = inner1d(a, b, axes=[(-1,), (-1,), ()], keepdims=False)
+        assert_array_equal(c, (a * b).sum(-1))
+        c = inner1d(a, b, axes=[(-1,), (-1,), (-1,)], keepdims=True)
+        assert_array_equal(c, (a * b).sum(-1, keepdims=True))
+        c = inner1d(a, b, axes=[0, 0], keepdims=False)
+        assert_array_equal(c, (a * b).sum(0))
+        c = inner1d(a, b, axes=[0, 0, 0], keepdims=True)
+        assert_array_equal(c, (a * b).sum(0, keepdims=True))
+        c = inner1d(a, b, axes=[0, 2], keepdims=False)
+        assert_array_equal(c, (a.transpose(1, 2, 0) * b).sum(-1))
+        c = inner1d(a, b, axes=[0, 2], keepdims=True)
+        assert_array_equal(c, (a.transpose(1, 2, 0) * b).sum(-1,
+                                                             keepdims=True))
+        c = inner1d(a, b, axes=[0, 2, 2], keepdims=True)
+        assert_array_equal(c, (a.transpose(1, 2, 0) * b).sum(-1,
+                                                             keepdims=True))
+        c = inner1d(a, b, axes=[0, 2, 0], keepdims=True)
+        assert_array_equal(c, (a * b.transpose(2, 0, 1)).sum(0, keepdims=True))
+        # Hardly useful, but should work.
+        c = inner1d(a, b, axes=[0, 2, 1], keepdims=True)
+        assert_array_equal(c, (a.transpose(1, 0, 2) * b.transpose(0, 2, 1))
+                           .sum(1, keepdims=True))
+        # Check with two core dimensions.
+        a = np.eye(3) * np.arange(4.)[:, np.newaxis, np.newaxis]
+        expected = uml.det(a)
+        c = uml.det(a, keepdims=False)
+        assert_array_equal(c, expected)
+        c = uml.det(a, keepdims=True)
+        assert_array_equal(c, expected[:, np.newaxis, np.newaxis])
+        a = np.eye(3) * np.arange(4.)[:, np.newaxis, np.newaxis]
+        expected_s, expected_l = uml.slogdet(a)
+        cs, cl = uml.slogdet(a, keepdims=False)
+        assert_array_equal(cs, expected_s)
+        assert_array_equal(cl, expected_l)
+        cs, cl = uml.slogdet(a, keepdims=True)
+        assert_array_equal(cs, expected_s[:, np.newaxis, np.newaxis])
+        assert_array_equal(cl, expected_l[:, np.newaxis, np.newaxis])
+        # Sanity check on innerwt.
+        a = np.arange(6).reshape((2, 3))
+        b = np.arange(10, 16).reshape((2, 3))
+        w = np.arange(20, 26).reshape((2, 3))
+        assert_array_equal(umt.innerwt(a, b, w, keepdims=True),
+                           np.sum(a * b * w, axis=-1, keepdims=True))
+        assert_array_equal(umt.innerwt(a, b, w, axis=0, keepdims=True),
+                           np.sum(a * b * w, axis=0, keepdims=True))
+        # Check errors.
+        # Not a boolean
+        assert_raises(TypeError, inner1d, a, b, keepdims='true')
+        # More than 1 core dimension, and core output dimensions.
+        mm = umt.matrix_multiply
+        assert_raises(TypeError, mm, a, b, keepdims=True)
+        assert_raises(TypeError, mm, a, b, keepdims=False)
+        # Regular ufuncs should not accept keepdims.
+        assert_raises(TypeError, np.add, 1., 1., keepdims=False)
+
+    def test_innerwt(self):
+        a = np.arange(6).reshape((2, 3))
+        b = np.arange(10, 16).reshape((2, 3))
+        w = np.arange(20, 26).reshape((2, 3))
+        assert_array_equal(umt.innerwt(a, b, w), np.sum(a*b*w, axis=-1))
+        a = np.arange(100, 124).reshape((2, 3, 4))
+        b = np.arange(200, 224).reshape((2, 3, 4))
+        w = np.arange(300, 324).reshape((2, 3, 4))
+        assert_array_equal(umt.innerwt(a, b, w), np.sum(a*b*w, axis=-1))
+
+    def test_innerwt_empty(self):
+        """Test generalized ufunc with zero-sized operands"""
+        a = np.array([], dtype='f8')
+        b = np.array([], dtype='f8')
+        w = np.array([], dtype='f8')
+        assert_array_equal(umt.innerwt(a, b, w), np.sum(a*b*w, axis=-1))
+
+    def test_cross1d(self):
+        """Test with fixed-sized signature."""
+        a = np.eye(3)
+        assert_array_equal(umt.cross1d(a, a), np.zeros((3, 3)))
+        out = np.zeros((3, 3))
+        result = umt.cross1d(a[0], a, out)
+        assert_(result is out)
+        assert_array_equal(result, np.vstack((np.zeros(3), a[2], -a[1])))
+        assert_raises(ValueError, umt.cross1d, np.eye(4), np.eye(4))
+        assert_raises(ValueError, umt.cross1d, a, np.arange(4.))
+        # Wrong output core dimension.
+        assert_raises(ValueError, umt.cross1d, a, np.arange(3.), np.zeros((3, 4)))
+        # Wrong output broadcast dimension (see gh-15139).
+        assert_raises(ValueError, umt.cross1d, a, np.arange(3.), np.zeros(3))
+
+    def test_can_ignore_signature(self):
+        # Comparing the effects of ? in signature:
+        # matrix_multiply: (m,n),(n,p)->(m,p)    # all must be there.
+        # matmul:        (m?,n),(n,p?)->(m?,p?)  # allow missing m, p.
+        mat = np.arange(12).reshape((2, 3, 2))
+        single_vec = np.arange(2)
+        col_vec = single_vec[:, np.newaxis]
+        col_vec_array = np.arange(8).reshape((2, 2, 2, 1)) + 1
+        # matrix @ single column vector with proper dimension
+        mm_col_vec = umt.matrix_multiply(mat, col_vec)
+        # matmul does the same thing
+        matmul_col_vec = umt.matmul(mat, col_vec)
+        assert_array_equal(matmul_col_vec, mm_col_vec)
+        # matrix @ vector without dimension making it a column vector.
+        # matrix multiply fails -> missing core dim.
+        assert_raises(ValueError, umt.matrix_multiply, mat, single_vec)
+        # matmul mimicker passes, and returns a vector.
+        matmul_col = umt.matmul(mat, single_vec)
+        assert_array_equal(matmul_col, mm_col_vec.squeeze())
+        # Now with a column array: same as for column vector,
+        # broadcasting sensibly.
+        mm_col_vec = umt.matrix_multiply(mat, col_vec_array)
+        matmul_col_vec = umt.matmul(mat, col_vec_array)
+        assert_array_equal(matmul_col_vec, mm_col_vec)
+        # As above, but for row vector
+        single_vec = np.arange(3)
+        row_vec = single_vec[np.newaxis, :]
+        row_vec_array = np.arange(24).reshape((4, 2, 1, 1, 3)) + 1
+        # row vector @ matrix
+        mm_row_vec = umt.matrix_multiply(row_vec, mat)
+        matmul_row_vec = umt.matmul(row_vec, mat)
+        assert_array_equal(matmul_row_vec, mm_row_vec)
+        # single row vector @ matrix
+        assert_raises(ValueError, umt.matrix_multiply, single_vec, mat)
+        matmul_row = umt.matmul(single_vec, mat)
+        assert_array_equal(matmul_row, mm_row_vec.squeeze())
+        # row vector array @ matrix
+        mm_row_vec = umt.matrix_multiply(row_vec_array, mat)
+        matmul_row_vec = umt.matmul(row_vec_array, mat)
+        assert_array_equal(matmul_row_vec, mm_row_vec)
+        # Now for vector combinations
+        # row vector @ column vector
+        col_vec = row_vec.T
+        col_vec_array = row_vec_array.swapaxes(-2, -1)
+        mm_row_col_vec = umt.matrix_multiply(row_vec, col_vec)
+        matmul_row_col_vec = umt.matmul(row_vec, col_vec)
+        assert_array_equal(matmul_row_col_vec, mm_row_col_vec)
+        # single row vector @ single col vector
+        assert_raises(ValueError, umt.matrix_multiply, single_vec, single_vec)
+        matmul_row_col = umt.matmul(single_vec, single_vec)
+        assert_array_equal(matmul_row_col, mm_row_col_vec.squeeze())
+        # row vector array @ matrix
+        mm_row_col_array = umt.matrix_multiply(row_vec_array, col_vec_array)
+        matmul_row_col_array = umt.matmul(row_vec_array, col_vec_array)
+        assert_array_equal(matmul_row_col_array, mm_row_col_array)
+        # Finally, check that things are *not* squeezed if one gives an
+        # output.
+        out = np.zeros_like(mm_row_col_array)
+        out = umt.matrix_multiply(row_vec_array, col_vec_array, out=out)
+        assert_array_equal(out, mm_row_col_array)
+        out[:] = 0
+        out = umt.matmul(row_vec_array, col_vec_array, out=out)
+        assert_array_equal(out, mm_row_col_array)
+        # And check one cannot put missing dimensions back.
+        out = np.zeros_like(mm_row_col_vec)
+        assert_raises(ValueError, umt.matrix_multiply, single_vec, single_vec,
+                      out)
+        # But fine for matmul, since it is just a broadcast.
+        out = umt.matmul(single_vec, single_vec, out)
+        assert_array_equal(out, mm_row_col_vec.squeeze())
+
+    def test_matrix_multiply(self):
+        self.compare_matrix_multiply_results(np.int64)
+        self.compare_matrix_multiply_results(np.double)
+
+    def test_matrix_multiply_umath_empty(self):
+        res = umt.matrix_multiply(np.ones((0, 10)), np.ones((10, 0)))
+        assert_array_equal(res, np.zeros((0, 0)))
+        res = umt.matrix_multiply(np.ones((10, 0)), np.ones((0, 10)))
+        assert_array_equal(res, np.zeros((10, 10)))
+
+    def compare_matrix_multiply_results(self, tp):
+        d1 = np.array(np.random.rand(2, 3, 4), dtype=tp)
+        d2 = np.array(np.random.rand(2, 3, 4), dtype=tp)
+        msg = "matrix multiply on type %s" % d1.dtype.name
+
+        def permute_n(n):
+            if n == 1:
+                return ([0],)
+            ret = ()
+            base = permute_n(n-1)
+            for perm in base:
+                for i in range(n):
+                    new = perm + [n-1]
+                    new[n-1] = new[i]
+                    new[i] = n-1
+                    ret += (new,)
+            return ret
+
+        def slice_n(n):
+            if n == 0:
+                return ((),)
+            ret = ()
+            base = slice_n(n-1)
+            for sl in base:
+                ret += (sl+(slice(None),),)
+                ret += (sl+(slice(0, 1),),)
+            return ret
+
+        def broadcastable(s1, s2):
+            return s1 == s2 or s1 == 1 or s2 == 1
+
+        permute_3 = permute_n(3)
+        slice_3 = slice_n(3) + ((slice(None, None, -1),)*3,)
+
+        ref = True
+        for p1 in permute_3:
+            for p2 in permute_3:
+                for s1 in slice_3:
+                    for s2 in slice_3:
+                        a1 = d1.transpose(p1)[s1]
+                        a2 = d2.transpose(p2)[s2]
+                        ref = ref and a1.base is not None
+                        ref = ref and a2.base is not None
+                        if (a1.shape[-1] == a2.shape[-2] and
+                                broadcastable(a1.shape[0], a2.shape[0])):
+                            assert_array_almost_equal(
+                                umt.matrix_multiply(a1, a2),
+                                np.sum(a2[..., np.newaxis].swapaxes(-3, -1) *
+                                       a1[..., np.newaxis,:], axis=-1),
+                                err_msg=msg + ' %s %s' % (str(a1.shape),
+                                                          str(a2.shape)))
+
+        assert_equal(ref, True, err_msg="reference check")
+
+    def test_euclidean_pdist(self):
+        a = np.arange(12, dtype=float).reshape(4, 3)
+        out = np.empty((a.shape[0] * (a.shape[0] - 1) // 2,), dtype=a.dtype)
+        umt.euclidean_pdist(a, out)
+        b = np.sqrt(np.sum((a[:, None] - a)**2, axis=-1))
+        b = b[~np.tri(a.shape[0], dtype=bool)]
+        assert_almost_equal(out, b)
+        # An output array is required to determine p with signature (n,d)->(p)
+        assert_raises(ValueError, umt.euclidean_pdist, a)
+
+    def test_cumsum(self):
+        a = np.arange(10)
+        result = umt.cumsum(a)
+        assert_array_equal(result, a.cumsum())
+
+    def test_object_logical(self):
+        a = np.array([3, None, True, False, "test", ""], dtype=object)
+        assert_equal(np.logical_or(a, None),
+                        np.array([x or None for x in a], dtype=object))
+        assert_equal(np.logical_or(a, True),
+                        np.array([x or True for x in a], dtype=object))
+        assert_equal(np.logical_or(a, 12),
+                        np.array([x or 12 for x in a], dtype=object))
+        assert_equal(np.logical_or(a, "blah"),
+                        np.array([x or "blah" for x in a], dtype=object))
+
+        assert_equal(np.logical_and(a, None),
+                        np.array([x and None for x in a], dtype=object))
+        assert_equal(np.logical_and(a, True),
+                        np.array([x and True for x in a], dtype=object))
+        assert_equal(np.logical_and(a, 12),
+                        np.array([x and 12 for x in a], dtype=object))
+        assert_equal(np.logical_and(a, "blah"),
+                        np.array([x and "blah" for x in a], dtype=object))
+
+        assert_equal(np.logical_not(a),
+                        np.array([not x for x in a], dtype=object))
+
+        assert_equal(np.logical_or.reduce(a), 3)
+        assert_equal(np.logical_and.reduce(a), None)
+
+    def test_object_comparison(self):
+        class HasComparisons:
+            def __eq__(self, other):
+                return '=='
+
+        arr0d = np.array(HasComparisons())
+        assert_equal(arr0d == arr0d, True)
+        assert_equal(np.equal(arr0d, arr0d), True)  # normal behavior is a cast
+
+        arr1d = np.array([HasComparisons()])
+        assert_equal(arr1d == arr1d, np.array([True]))
+        assert_equal(np.equal(arr1d, arr1d), np.array([True]))  # normal behavior is a cast
+        assert_equal(np.equal(arr1d, arr1d, dtype=object), np.array(['==']))
+
+    def test_object_array_reduction(self):
+        # Reductions on object arrays
+        a = np.array(['a', 'b', 'c'], dtype=object)
+        assert_equal(np.sum(a), 'abc')
+        assert_equal(np.max(a), 'c')
+        assert_equal(np.min(a), 'a')
+        a = np.array([True, False, True], dtype=object)
+        assert_equal(np.sum(a), 2)
+        assert_equal(np.prod(a), 0)
+        assert_equal(np.any(a), True)
+        assert_equal(np.all(a), False)
+        assert_equal(np.max(a), True)
+        assert_equal(np.min(a), False)
+        assert_equal(np.array([[1]], dtype=object).sum(), 1)
+        assert_equal(np.array([[[1, 2]]], dtype=object).sum((0, 1)), [1, 2])
+        assert_equal(np.array([1], dtype=object).sum(initial=1), 2)
+        assert_equal(np.array([[1], [2, 3]], dtype=object)
+                     .sum(initial=[0], where=[False, True]), [0, 2, 3])
+
+    def test_object_array_accumulate_inplace(self):
+        # Checks that in-place accumulates work, see also gh-7402
+        arr = np.ones(4, dtype=object)
+        arr[:] = [[1] for i in range(4)]
+        # Twice reproduced also for tuples:
+        np.add.accumulate(arr, out=arr)
+        np.add.accumulate(arr, out=arr)
+        assert_array_equal(arr,
+                           np.array([[1]*i for i in [1, 3, 6, 10]], dtype=object),
+                          )
+
+        # And the same if the axis argument is used
+        arr = np.ones((2, 4), dtype=object)
+        arr[0, :] = [[2] for i in range(4)]
+        np.add.accumulate(arr, out=arr, axis=-1)
+        np.add.accumulate(arr, out=arr, axis=-1)
+        assert_array_equal(arr[0, :],
+                           np.array([[2]*i for i in [1, 3, 6, 10]], dtype=object),
+                          )
+
+    def test_object_array_accumulate_failure(self):
+        # Typical accumulation on object works as expected:
+        res = np.add.accumulate(np.array([1, 0, 2], dtype=object))
+        assert_array_equal(res, np.array([1, 1, 3], dtype=object))
+        # But errors are propagated from the inner-loop if they occur:
+        with pytest.raises(TypeError):
+            np.add.accumulate([1, None, 2])
+
+    def test_object_array_reduceat_inplace(self):
+        # Checks that in-place reduceats work, see also gh-7465
+        arr = np.empty(4, dtype=object)
+        arr[:] = [[1] for i in range(4)]
+        out = np.empty(4, dtype=object)
+        out[:] = [[1] for i in range(4)]
+        np.add.reduceat(arr, np.arange(4), out=arr)
+        np.add.reduceat(arr, np.arange(4), out=arr)
+        assert_array_equal(arr, out)
+
+        # And the same if the axis argument is used
+        arr = np.ones((2, 4), dtype=object)
+        arr[0, :] = [[2] for i in range(4)]
+        out = np.ones((2, 4), dtype=object)
+        out[0, :] = [[2] for i in range(4)]
+        np.add.reduceat(arr, np.arange(4), out=arr, axis=-1)
+        np.add.reduceat(arr, np.arange(4), out=arr, axis=-1)
+        assert_array_equal(arr, out)
+
+    def test_object_array_reduceat_failure(self):
+        # Reduceat works as expected when no invalid operation occurs (None is
+        # not involved in an operation here)
+        res = np.add.reduceat(np.array([1, None, 2], dtype=object), [1, 2])
+        assert_array_equal(res, np.array([None, 2], dtype=object))
+        # But errors when None would be involved in an operation:
+        with pytest.raises(TypeError):
+            np.add.reduceat([1, None, 2], [0, 2])
+
+    def test_zerosize_reduction(self):
+        # Test with default dtype and object dtype
+        for a in [[], np.array([], dtype=object)]:
+            assert_equal(np.sum(a), 0)
+            assert_equal(np.prod(a), 1)
+            assert_equal(np.any(a), False)
+            assert_equal(np.all(a), True)
+            assert_raises(ValueError, np.max, a)
+            assert_raises(ValueError, np.min, a)
+
+    def test_axis_out_of_bounds(self):
+        a = np.array([False, False])
+        assert_raises(np.AxisError, a.all, axis=1)
+        a = np.array([False, False])
+        assert_raises(np.AxisError, a.all, axis=-2)
+
+        a = np.array([False, False])
+        assert_raises(np.AxisError, a.any, axis=1)
+        a = np.array([False, False])
+        assert_raises(np.AxisError, a.any, axis=-2)
+
+    def test_scalar_reduction(self):
+        # The functions 'sum', 'prod', etc allow specifying axis=0
+        # even for scalars
+        assert_equal(np.sum(3, axis=0), 3)
+        assert_equal(np.prod(3.5, axis=0), 3.5)
+        assert_equal(np.any(True, axis=0), True)
+        assert_equal(np.all(False, axis=0), False)
+        assert_equal(np.max(3, axis=0), 3)
+        assert_equal(np.min(2.5, axis=0), 2.5)
+
+        # Check scalar behaviour for ufuncs without an identity
+        assert_equal(np.power.reduce(3), 3)
+
+        # Make sure that scalars are coming out from this operation
+        assert_(type(np.prod(np.float32(2.5), axis=0)) is np.float32)
+        assert_(type(np.sum(np.float32(2.5), axis=0)) is np.float32)
+        assert_(type(np.max(np.float32(2.5), axis=0)) is np.float32)
+        assert_(type(np.min(np.float32(2.5), axis=0)) is np.float32)
+
+        # check if scalars/0-d arrays get cast
+        assert_(type(np.any(0, axis=0)) is np.bool_)
+
+        # assert that 0-d arrays get wrapped
+        class MyArray(np.ndarray):
+            pass
+        a = np.array(1).view(MyArray)
+        assert_(type(np.any(a)) is MyArray)
+
+    def test_casting_out_param(self):
+        # Test that it's possible to do casts on output
+        a = np.ones((200, 100), np.int64)
+        b = np.ones((200, 100), np.int64)
+        c = np.ones((200, 100), np.float64)
+        np.add(a, b, out=c)
+        assert_equal(c, 2)
+
+        a = np.zeros(65536)
+        b = np.zeros(65536, dtype=np.float32)
+        np.subtract(a, 0, out=b)
+        assert_equal(b, 0)
+
+    def test_where_param(self):
+        # Test that the where= ufunc parameter works with regular arrays
+        a = np.arange(7)
+        b = np.ones(7)
+        c = np.zeros(7)
+        np.add(a, b, out=c, where=(a % 2 == 1))
+        assert_equal(c, [0, 2, 0, 4, 0, 6, 0])
+
+        a = np.arange(4).reshape(2, 2) + 2
+        np.power(a, [2, 3], out=a, where=[[0, 1], [1, 0]])
+        assert_equal(a, [[2, 27], [16, 5]])
+        # Broadcasting the where= parameter
+        np.subtract(a, 2, out=a, where=[True, False])
+        assert_equal(a, [[0, 27], [14, 5]])
+
+    def test_where_param_buffer_output(self):
+        # This test is temporarily skipped because it requires
+        # adding masking features to the nditer to work properly
+
+        # With casting on output
+        a = np.ones(10, np.int64)
+        b = np.ones(10, np.int64)
+        c = 1.5 * np.ones(10, np.float64)
+        np.add(a, b, out=c, where=[1, 0, 0, 1, 0, 0, 1, 1, 1, 0])
+        assert_equal(c, [2, 1.5, 1.5, 2, 1.5, 1.5, 2, 2, 2, 1.5])
+
+    def test_where_param_alloc(self):
+        # With casting and allocated output
+        a = np.array([1], dtype=np.int64)
+        m = np.array([True], dtype=bool)
+        assert_equal(np.sqrt(a, where=m), [1])
+
+        # No casting and allocated output
+        a = np.array([1], dtype=np.float64)
+        m = np.array([True], dtype=bool)
+        assert_equal(np.sqrt(a, where=m), [1])
+
+    def test_where_with_broadcasting(self):
+        # See gh-17198
+        a = np.random.random((5000, 4))
+        b = np.random.random((5000, 1))
+
+        where = a > 0.3
+        out = np.full_like(a, 0)
+        np.less(a, b, where=where, out=out)
+        b_where = np.broadcast_to(b, a.shape)[where]
+        assert_array_equal((a[where] < b_where), out[where].astype(bool))
+        assert not out[~where].any()  # outside mask, out remains all 0
+
+    def check_identityless_reduction(self, a):
+        # np.minimum.reduce is an identityless reduction
+
+        # Verify that it sees the zero at various positions
+        a[...] = 1
+        a[1, 0, 0] = 0
+        assert_equal(np.minimum.reduce(a, axis=None), 0)
+        assert_equal(np.minimum.reduce(a, axis=(0, 1)), [0, 1, 1, 1])
+        assert_equal(np.minimum.reduce(a, axis=(0, 2)), [0, 1, 1])
+        assert_equal(np.minimum.reduce(a, axis=(1, 2)), [1, 0])
+        assert_equal(np.minimum.reduce(a, axis=0),
+                                    [[0, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=1),
+                                    [[1, 1, 1, 1], [0, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=2),
+                                    [[1, 1, 1], [0, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=()), a)
+
+        a[...] = 1
+        a[0, 1, 0] = 0
+        assert_equal(np.minimum.reduce(a, axis=None), 0)
+        assert_equal(np.minimum.reduce(a, axis=(0, 1)), [0, 1, 1, 1])
+        assert_equal(np.minimum.reduce(a, axis=(0, 2)), [1, 0, 1])
+        assert_equal(np.minimum.reduce(a, axis=(1, 2)), [0, 1])
+        assert_equal(np.minimum.reduce(a, axis=0),
+                                    [[1, 1, 1, 1], [0, 1, 1, 1], [1, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=1),
+                                    [[0, 1, 1, 1], [1, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=2),
+                                    [[1, 0, 1], [1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=()), a)
+
+        a[...] = 1
+        a[0, 0, 1] = 0
+        assert_equal(np.minimum.reduce(a, axis=None), 0)
+        assert_equal(np.minimum.reduce(a, axis=(0, 1)), [1, 0, 1, 1])
+        assert_equal(np.minimum.reduce(a, axis=(0, 2)), [0, 1, 1])
+        assert_equal(np.minimum.reduce(a, axis=(1, 2)), [0, 1])
+        assert_equal(np.minimum.reduce(a, axis=0),
+                                    [[1, 0, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=1),
+                                    [[1, 0, 1, 1], [1, 1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=2),
+                                    [[0, 1, 1], [1, 1, 1]])
+        assert_equal(np.minimum.reduce(a, axis=()), a)
+
+    @requires_memory(6 * 1024**3)
+    @pytest.mark.skipif(sys.maxsize < 2**32,
+            reason="test array too large for 32bit platform")
+    def test_identityless_reduction_huge_array(self):
+        # Regression test for gh-20921 (copying identity incorrectly failed)
+        arr = np.zeros((2, 2**31), 'uint8')
+        arr[:, 0] = [1, 3]
+        arr[:, -1] = [4, 1]
+        res = np.maximum.reduce(arr, axis=0)
+        del arr
+        assert res[0] == 3
+        assert res[-1] == 4
+
+    def test_identityless_reduction_corder(self):
+        a = np.empty((2, 3, 4), order='C')
+        self.check_identityless_reduction(a)
+
+    def test_identityless_reduction_forder(self):
+        a = np.empty((2, 3, 4), order='F')
+        self.check_identityless_reduction(a)
+
+    def test_identityless_reduction_otherorder(self):
+        a = np.empty((2, 4, 3), order='C').swapaxes(1, 2)
+        self.check_identityless_reduction(a)
+
+    def test_identityless_reduction_noncontig(self):
+        a = np.empty((3, 5, 4), order='C').swapaxes(1, 2)
+        a = a[1:, 1:, 1:]
+        self.check_identityless_reduction(a)
+
+    def test_identityless_reduction_noncontig_unaligned(self):
+        a = np.empty((3*4*5*8 + 1,), dtype='i1')
+        a = a[1:].view(dtype='f8')
+        a.shape = (3, 4, 5)
+        a = a[1:, 1:, 1:]
+        self.check_identityless_reduction(a)
+
+    def test_reduce_identity_depends_on_loop(self):
+        """
+        The type of the result should always depend on the selected loop, not
+        necessarily the output (only relevant for object arrays).
+        """
+        # For an object loop, the default value 0 with type int is used:
+        assert type(np.add.reduce([], dtype=object)) is int
+        out = np.array(None, dtype=object)
+        # When the loop is float64 but `out` is object this does not happen,
+        # the result is float64 cast to object (which gives Python `float`).
+        np.add.reduce([], out=out, dtype=np.float64)
+        assert type(out[()]) is float
+
+    def test_initial_reduction(self):
+        # np.minimum.reduce is an identityless reduction
+
+        # For cases like np.maximum(np.abs(...), initial=0)
+        # More generally, a supremum over non-negative numbers.
+        assert_equal(np.maximum.reduce([], initial=0), 0)
+
+        # For cases like reduction of an empty array over the reals.
+        assert_equal(np.minimum.reduce([], initial=np.inf), np.inf)
+        assert_equal(np.maximum.reduce([], initial=-np.inf), -np.inf)
+
+        # Random tests
+        assert_equal(np.minimum.reduce([5], initial=4), 4)
+        assert_equal(np.maximum.reduce([4], initial=5), 5)
+        assert_equal(np.maximum.reduce([5], initial=4), 5)
+        assert_equal(np.minimum.reduce([4], initial=5), 4)
+
+        # Check initial=None raises ValueError for both types of ufunc reductions
+        assert_raises(ValueError, np.minimum.reduce, [], initial=None)
+        assert_raises(ValueError, np.add.reduce, [], initial=None)
+        # Also in the somewhat special object case:
+        with pytest.raises(ValueError):
+            np.add.reduce([], initial=None, dtype=object)
+
+        # Check that np._NoValue gives default behavior.
+        assert_equal(np.add.reduce([], initial=np._NoValue), 0)
+
+        # Check that initial kwarg behaves as intended for dtype=object
+        a = np.array([10], dtype=object)
+        res = np.add.reduce(a, initial=5)
+        assert_equal(res, 15)
+
+    def test_empty_reduction_and_idenity(self):
+        arr = np.zeros((0, 5))
+        # OK, since the reduction itself is *not* empty, the result is
+        assert np.true_divide.reduce(arr, axis=1).shape == (0,)
+        # Not OK, the reduction itself is empty and we have no idenity
+        with pytest.raises(ValueError):
+            np.true_divide.reduce(arr, axis=0)
+
+        # Test that an empty reduction fails also if the result is empty
+        arr = np.zeros((0, 0, 5))
+        with pytest.raises(ValueError):
+            np.true_divide.reduce(arr, axis=1)
+
+        # Division reduction makes sense with `initial=1` (empty or not):
+        res = np.true_divide.reduce(arr, axis=1, initial=1)
+        assert_array_equal(res, np.ones((0, 5)))
+
+    @pytest.mark.parametrize('axis', (0, 1, None))
+    @pytest.mark.parametrize('where', (np.array([False, True, True]),
+                                       np.array([[True], [False], [True]]),
+                                       np.array([[True, False, False],
+                                                 [False, True, False],
+                                                 [False, True, True]])))
+    def test_reduction_with_where(self, axis, where):
+        a = np.arange(9.).reshape(3, 3)
+        a_copy = a.copy()
+        a_check = np.zeros_like(a)
+        np.positive(a, out=a_check, where=where)
+
+        res = np.add.reduce(a, axis=axis, where=where)
+        check = a_check.sum(axis)
+        assert_equal(res, check)
+        # Check we do not overwrite elements of a internally.
+        assert_array_equal(a, a_copy)
+
+    @pytest.mark.parametrize(('axis', 'where'),
+                             ((0, np.array([True, False, True])),
+                              (1, [True, True, False]),
+                              (None, True)))
+    @pytest.mark.parametrize('initial', (-np.inf, 5.))
+    def test_reduction_with_where_and_initial(self, axis, where, initial):
+        a = np.arange(9.).reshape(3, 3)
+        a_copy = a.copy()
+        a_check = np.full(a.shape, -np.inf)
+        np.positive(a, out=a_check, where=where)
+
+        res = np.maximum.reduce(a, axis=axis, where=where, initial=initial)
+        check = a_check.max(axis, initial=initial)
+        assert_equal(res, check)
+
+    def test_reduction_where_initial_needed(self):
+        a = np.arange(9.).reshape(3, 3)
+        m = [False, True, False]
+        assert_raises(ValueError, np.maximum.reduce, a, where=m)
+
+    def test_identityless_reduction_nonreorderable(self):
+        a = np.array([[8.0, 2.0, 2.0], [1.0, 0.5, 0.25]])
+
+        res = np.divide.reduce(a, axis=0)
+        assert_equal(res, [8.0, 4.0, 8.0])
+
+        res = np.divide.reduce(a, axis=1)
+        assert_equal(res, [2.0, 8.0])
+
+        res = np.divide.reduce(a, axis=())
+        assert_equal(res, a)
+
+        assert_raises(ValueError, np.divide.reduce, a, axis=(0, 1))
+
+    def test_reduce_zero_axis(self):
+        # If we have a n x m array and do a reduction with axis=1, then we are
+        # doing n reductions, and each reduction takes an m-element array. For
+        # a reduction operation without an identity, then:
+        #   n > 0, m > 0: fine
+        #   n = 0, m > 0: fine, doing 0 reductions of m-element arrays
+        #   n > 0, m = 0: can't reduce a 0-element array, ValueError
+        #   n = 0, m = 0: can't reduce a 0-element array, ValueError (for
+        #     consistency with the above case)
+        # This test doesn't actually look at return values, it just checks to
+        # make sure that error we get an error in exactly those cases where we
+        # expect one, and assumes the calculations themselves are done
+        # correctly.
+
+        def ok(f, *args, **kwargs):
+            f(*args, **kwargs)
+
+        def err(f, *args, **kwargs):
+            assert_raises(ValueError, f, *args, **kwargs)
+
+        def t(expect, func, n, m):
+            expect(func, np.zeros((n, m)), axis=1)
+            expect(func, np.zeros((m, n)), axis=0)
+            expect(func, np.zeros((n // 2, n // 2, m)), axis=2)
+            expect(func, np.zeros((n // 2, m, n // 2)), axis=1)
+            expect(func, np.zeros((n, m // 2, m // 2)), axis=(1, 2))
+            expect(func, np.zeros((m // 2, n, m // 2)), axis=(0, 2))
+            expect(func, np.zeros((m // 3, m // 3, m // 3,
+                                  n // 2, n // 2)),
+                                 axis=(0, 1, 2))
+            # Check what happens if the inner (resp. outer) dimensions are a
+            # mix of zero and non-zero:
+            expect(func, np.zeros((10, m, n)), axis=(0, 1))
+            expect(func, np.zeros((10, n, m)), axis=(0, 2))
+            expect(func, np.zeros((m, 10, n)), axis=0)
+            expect(func, np.zeros((10, m, n)), axis=1)
+            expect(func, np.zeros((10, n, m)), axis=2)
+
+        # np.maximum is just an arbitrary ufunc with no reduction identity
+        assert_equal(np.maximum.identity, None)
+        t(ok, np.maximum.reduce, 30, 30)
+        t(ok, np.maximum.reduce, 0, 30)
+        t(err, np.maximum.reduce, 30, 0)
+        t(err, np.maximum.reduce, 0, 0)
+        err(np.maximum.reduce, [])
+        np.maximum.reduce(np.zeros((0, 0)), axis=())
+
+        # all of the combinations are fine for a reduction that has an
+        # identity
+        t(ok, np.add.reduce, 30, 30)
+        t(ok, np.add.reduce, 0, 30)
+        t(ok, np.add.reduce, 30, 0)
+        t(ok, np.add.reduce, 0, 0)
+        np.add.reduce([])
+        np.add.reduce(np.zeros((0, 0)), axis=())
+
+        # OTOH, accumulate always makes sense for any combination of n and m,
+        # because it maps an m-element array to an m-element array. These
+        # tests are simpler because accumulate doesn't accept multiple axes.
+        for uf in (np.maximum, np.add):
+            uf.accumulate(np.zeros((30, 0)), axis=0)
+            uf.accumulate(np.zeros((0, 30)), axis=0)
+            uf.accumulate(np.zeros((30, 30)), axis=0)
+            uf.accumulate(np.zeros((0, 0)), axis=0)
+
+    def test_safe_casting(self):
+        # In old versions of numpy, in-place operations used the 'unsafe'
+        # casting rules. In versions >= 1.10, 'same_kind' is the
+        # default and an exception is raised instead of a warning.
+        # when 'same_kind' is not satisfied.
+        a = np.array([1, 2, 3], dtype=int)
+        # Non-in-place addition is fine
+        assert_array_equal(assert_no_warnings(np.add, a, 1.1),
+                           [2.1, 3.1, 4.1])
+        assert_raises(TypeError, np.add, a, 1.1, out=a)
+
+        def add_inplace(a, b):
+            a += b
+
+        assert_raises(TypeError, add_inplace, a, 1.1)
+        # Make sure that explicitly overriding the exception is allowed:
+        assert_no_warnings(np.add, a, 1.1, out=a, casting="unsafe")
+        assert_array_equal(a, [2, 3, 4])
+
+    def test_ufunc_custom_out(self):
+        # Test ufunc with built in input types and custom output type
+
+        a = np.array([0, 1, 2], dtype='i8')
+        b = np.array([0, 1, 2], dtype='i8')
+        c = np.empty(3, dtype=_rational_tests.rational)
+
+        # Output must be specified so numpy knows what
+        # ufunc signature to look for
+        result = _rational_tests.test_add(a, b, c)
+        target = np.array([0, 2, 4], dtype=_rational_tests.rational)
+        assert_equal(result, target)
+
+        # The new resolution means that we can (usually) find custom loops
+        # as long as they match exactly:
+        result = _rational_tests.test_add(a, b)
+        assert_equal(result, target)
+
+        # This works even more generally, so long the default common-dtype
+        # promoter works out:
+        result = _rational_tests.test_add(a, b.astype(np.uint16), out=c)
+        assert_equal(result, target)
+
+        # But, it can be fooled, e.g. (use scalars, which forces legacy
+        # type resolution to kick in, which then fails):
+        with assert_raises(TypeError):
+            _rational_tests.test_add(a, np.uint16(2))
+
+    def test_operand_flags(self):
+        a = np.arange(16, dtype='l').reshape(4, 4)
+        b = np.arange(9, dtype='l').reshape(3, 3)
+        opflag_tests.inplace_add(a[:-1, :-1], b)
+        assert_equal(a, np.array([[0, 2, 4, 3], [7, 9, 11, 7],
+            [14, 16, 18, 11], [12, 13, 14, 15]], dtype='l'))
+
+        a = np.array(0)
+        opflag_tests.inplace_add(a, 3)
+        assert_equal(a, 3)
+        opflag_tests.inplace_add(a, [3, 4])
+        assert_equal(a, 10)
+
+    def test_struct_ufunc(self):
+        import numpy.core._struct_ufunc_tests as struct_ufunc
+
+        a = np.array([(1, 2, 3)], dtype='u8,u8,u8')
+        b = np.array([(1, 2, 3)], dtype='u8,u8,u8')
+
+        result = struct_ufunc.add_triplet(a, b)
+        assert_equal(result, np.array([(2, 4, 6)], dtype='u8,u8,u8'))
+        assert_raises(RuntimeError, struct_ufunc.register_fail)
+
+    def test_custom_ufunc(self):
+        a = np.array(
+            [_rational_tests.rational(1, 2),
+             _rational_tests.rational(1, 3),
+             _rational_tests.rational(1, 4)],
+            dtype=_rational_tests.rational)
+        b = np.array(
+            [_rational_tests.rational(1, 2),
+             _rational_tests.rational(1, 3),
+             _rational_tests.rational(1, 4)],
+            dtype=_rational_tests.rational)
+
+        result = _rational_tests.test_add_rationals(a, b)
+        expected = np.array(
+            [_rational_tests.rational(1),
+             _rational_tests.rational(2, 3),
+             _rational_tests.rational(1, 2)],
+            dtype=_rational_tests.rational)
+        assert_equal(result, expected)
+
+    def test_custom_ufunc_forced_sig(self):
+        # gh-9351 - looking for a non-first userloop would previously hang
+        with assert_raises(TypeError):
+            np.multiply(_rational_tests.rational(1), 1,
+                        signature=(_rational_tests.rational, int, None))
+
+    def test_custom_array_like(self):
+
+        class MyThing:
+            __array_priority__ = 1000
+
+            rmul_count = 0
+            getitem_count = 0
+
+            def __init__(self, shape):
+                self.shape = shape
+
+            def __len__(self):
+                return self.shape[0]
+
+            def __getitem__(self, i):
+                MyThing.getitem_count += 1
+                if not isinstance(i, tuple):
+                    i = (i,)
+                if len(i) > self.ndim:
+                    raise IndexError("boo")
+
+                return MyThing(self.shape[len(i):])
+
+            def __rmul__(self, other):
+                MyThing.rmul_count += 1
+                return self
+
+        np.float64(5)*MyThing((3, 3))
+        assert_(MyThing.rmul_count == 1, MyThing.rmul_count)
+        assert_(MyThing.getitem_count <= 2, MyThing.getitem_count)
+
+    @pytest.mark.parametrize("a", (
+                             np.arange(10, dtype=int),
+                             np.arange(10, dtype=_rational_tests.rational),
+                             ))
+    def test_ufunc_at_basic(self, a):
+
+        aa = a.copy()
+        np.add.at(aa, [2, 5, 2], 1)
+        assert_equal(aa, [0, 1, 4, 3, 4, 6, 6, 7, 8, 9])
+
+        with pytest.raises(ValueError):
+            # missing second operand
+            np.add.at(aa, [2, 5, 3])
+
+        aa = a.copy()
+        np.negative.at(aa, [2, 5, 3])
+        assert_equal(aa, [0, 1, -2, -3, 4, -5, 6, 7, 8, 9])
+
+        aa = a.copy()
+        b = np.array([100, 100, 100])
+        np.add.at(aa, [2, 5, 2], b)
+        assert_equal(aa, [0, 1, 202, 3, 4, 105, 6, 7, 8, 9])
+
+        with pytest.raises(ValueError):
+            # extraneous second operand
+            np.negative.at(a, [2, 5, 3], [1, 2, 3])
+
+        with pytest.raises(ValueError):
+            # second operand cannot be converted to an array
+            np.add.at(a, [2, 5, 3], [[1, 2], 1])
+
+    # ufuncs with indexed loops for performance in ufunc.at
+    indexed_ufuncs = [np.add, np.subtract, np.multiply, np.floor_divide,
+                      np.maximum, np.minimum, np.fmax, np.fmin]
+
+    @pytest.mark.parametrize(
+                "typecode", np.typecodes['AllInteger'] + np.typecodes['Float'])
+    @pytest.mark.parametrize("ufunc", indexed_ufuncs)
+    def test_ufunc_at_inner_loops(self, typecode, ufunc):
+        if ufunc is np.divide and typecode in np.typecodes['AllInteger']:
+            # Avoid divide-by-zero and inf for integer divide
+            a = np.ones(100, dtype=typecode)
+            indx = np.random.randint(100, size=30, dtype=np.intp)
+            vals = np.arange(1, 31, dtype=typecode)
+        else:
+            a = np.ones(1000, dtype=typecode)
+            indx = np.random.randint(1000, size=3000, dtype=np.intp)
+            vals = np.arange(3000, dtype=typecode)
+        atag = a.copy()
+        # Do the calculation twice and compare the answers
+        with warnings.catch_warnings(record=True) as w_at:
+            warnings.simplefilter('always')
+            ufunc.at(a, indx, vals)
+        with warnings.catch_warnings(record=True) as w_loop:
+            warnings.simplefilter('always')
+            for i, v in zip(indx, vals):
+                # Make sure all the work happens inside the ufunc
+                # in order to duplicate error/warning handling
+                ufunc(atag[i], v, out=atag[i:i+1], casting="unsafe")
+        assert_equal(atag, a)
+        # If w_loop warned, make sure w_at warned as well
+        if len(w_loop) > 0:
+            #
+            assert len(w_at) > 0
+            assert w_at[0].category == w_loop[0].category
+            assert str(w_at[0].message)[:10] == str(w_loop[0].message)[:10]
+
+    @pytest.mark.parametrize("typecode", np.typecodes['Complex'])
+    @pytest.mark.parametrize("ufunc", [np.add, np.subtract, np.multiply])
+    def test_ufunc_at_inner_loops_complex(self, typecode, ufunc):
+        a = np.ones(10, dtype=typecode)
+        indx = np.concatenate([np.ones(6, dtype=np.intp),
+                               np.full(18, 4, dtype=np.intp)])
+        value = a.dtype.type(1j)
+        ufunc.at(a, indx, value)
+        expected = np.ones_like(a)
+        if ufunc is np.multiply:
+            expected[1] = expected[4] = -1
+        else:
+            expected[1] += 6 * (value if ufunc is np.add else -value)
+            expected[4] += 18 * (value if ufunc is np.add else -value)
+
+        assert_array_equal(a, expected)
+
+    def test_ufunc_at_ellipsis(self):
+        # Make sure the indexed loop check does not choke on iters
+        # with subspaces
+        arr = np.zeros(5)
+        np.add.at(arr, slice(None), np.ones(5))
+        assert_array_equal(arr, np.ones(5))
+
+    def test_ufunc_at_negative(self):
+        arr = np.ones(5, dtype=np.int32)
+        indx = np.arange(5)
+        umt.indexed_negative.at(arr, indx)
+        # If it is [-1, -1, -1, -100, 0] then the regular strided loop was used
+        assert np.all(arr == [-1, -1, -1, -200, -1])
+
+    def test_ufunc_at_large(self):
+        # issue gh-23457
+        indices = np.zeros(8195, dtype=np.int16)
+        b = np.zeros(8195, dtype=float)
+        b[0] = 10
+        b[1] = 5
+        b[8192:] = 100
+        a = np.zeros(1, dtype=float)
+        np.add.at(a, indices, b)
+        assert a[0] == b.sum()
+
+    def test_cast_index_fastpath(self):
+        arr = np.zeros(10)
+        values = np.ones(100000)
+        # index must be cast, which may be buffered in chunks:
+        index = np.zeros(len(values), dtype=np.uint8)
+        np.add.at(arr, index, values)
+        assert arr[0] == len(values)
+
+    @pytest.mark.parametrize("value", [
+        np.ones(1), np.ones(()), np.float64(1.), 1.])
+    def test_ufunc_at_scalar_value_fastpath(self, value):
+        arr = np.zeros(1000)
+        # index must be cast, which may be buffered in chunks:
+        index = np.repeat(np.arange(1000), 2)
+        np.add.at(arr, index, value)
+        assert_array_equal(arr, np.full_like(arr, 2 * value))
+
+    def test_ufunc_at_multiD(self):
+        a = np.arange(9).reshape(3, 3)
+        b = np.array([[100, 100, 100], [200, 200, 200], [300, 300, 300]])
+        np.add.at(a, (slice(None), [1, 2, 1]), b)
+        assert_equal(a, [[0, 201, 102], [3, 404, 205], [6, 607, 308]])
+
+        a = np.arange(27).reshape(3, 3, 3)
+        b = np.array([100, 200, 300])
+        np.add.at(a, (slice(None), slice(None), [1, 2, 1]), b)
+        assert_equal(a,
+            [[[0, 401, 202],
+              [3, 404, 205],
+              [6, 407, 208]],
+
+             [[9, 410, 211],
+              [12, 413, 214],
+              [15, 416, 217]],
+
+             [[18, 419, 220],
+              [21, 422, 223],
+              [24, 425, 226]]])
+
+        a = np.arange(9).reshape(3, 3)
+        b = np.array([[100, 100, 100], [200, 200, 200], [300, 300, 300]])
+        np.add.at(a, ([1, 2, 1], slice(None)), b)
+        assert_equal(a, [[0, 1, 2], [403, 404, 405], [206, 207, 208]])
+
+        a = np.arange(27).reshape(3, 3, 3)
+        b = np.array([100, 200, 300])
+        np.add.at(a, (slice(None), [1, 2, 1], slice(None)), b)
+        assert_equal(a,
+            [[[0,  1,  2],
+              [203, 404, 605],
+              [106, 207, 308]],
+
+             [[9,  10, 11],
+              [212, 413, 614],
+              [115, 216, 317]],
+
+             [[18, 19, 20],
+              [221, 422, 623],
+              [124, 225, 326]]])
+
+        a = np.arange(9).reshape(3, 3)
+        b = np.array([100, 200, 300])
+        np.add.at(a, (0, [1, 2, 1]), b)
+        assert_equal(a, [[0, 401, 202], [3, 4, 5], [6, 7, 8]])
+
+        a = np.arange(27).reshape(3, 3, 3)
+        b = np.array([100, 200, 300])
+        np.add.at(a, ([1, 2, 1], 0, slice(None)), b)
+        assert_equal(a,
+            [[[0,  1,  2],
+              [3,  4,  5],
+              [6,  7,  8]],
+
+             [[209, 410, 611],
+              [12,  13, 14],
+              [15,  16, 17]],
+
+             [[118, 219, 320],
+              [21,  22, 23],
+              [24,  25, 26]]])
+
+        a = np.arange(27).reshape(3, 3, 3)
+        b = np.array([100, 200, 300])
+        np.add.at(a, (slice(None), slice(None), slice(None)), b)
+        assert_equal(a,
+            [[[100, 201, 302],
+              [103, 204, 305],
+              [106, 207, 308]],
+
+             [[109, 210, 311],
+              [112, 213, 314],
+              [115, 216, 317]],
+
+             [[118, 219, 320],
+              [121, 222, 323],
+              [124, 225, 326]]])
+
+    def test_ufunc_at_0D(self):
+        a = np.array(0)
+        np.add.at(a, (), 1)
+        assert_equal(a, 1)
+
+        assert_raises(IndexError, np.add.at, a, 0, 1)
+        assert_raises(IndexError, np.add.at, a, [], 1)
+
+    def test_ufunc_at_dtypes(self):
+        # Test mixed dtypes
+        a = np.arange(10)
+        np.power.at(a, [1, 2, 3, 2], 3.5)
+        assert_equal(a, np.array([0, 1, 4414, 46, 4, 5, 6, 7, 8, 9]))
+
+    def test_ufunc_at_boolean(self):
+        # Test boolean indexing and boolean ufuncs
+        a = np.arange(10)
+        index = a % 2 == 0
+        np.equal.at(a, index, [0, 2, 4, 6, 8])
+        assert_equal(a, [1, 1, 1, 3, 1, 5, 1, 7, 1, 9])
+
+        # Test unary operator
+        a = np.arange(10, dtype='u4')
+        np.invert.at(a, [2, 5, 2])
+        assert_equal(a, [0, 1, 2, 3, 4, 5 ^ 0xffffffff, 6, 7, 8, 9])
+
+    def test_ufunc_at_advanced(self):
+        # Test empty subspace
+        orig = np.arange(4)
+        a = orig[:, None][:, 0:0]
+        np.add.at(a, [0, 1], 3)
+        assert_array_equal(orig, np.arange(4))
+
+        # Test with swapped byte order
+        index = np.array([1, 2, 1], np.dtype('i').newbyteorder())
+        values = np.array([1, 2, 3, 4], np.dtype('f').newbyteorder())
+        np.add.at(values, index, 3)
+        assert_array_equal(values, [1, 8, 6, 4])
+
+        # Test exception thrown
+        values = np.array(['a', 1], dtype=object)
+        assert_raises(TypeError, np.add.at, values, [0, 1], 1)
+        assert_array_equal(values, np.array(['a', 1], dtype=object))
+
+        # Test multiple output ufuncs raise error, gh-5665
+        assert_raises(ValueError, np.modf.at, np.arange(10), [1])
+
+        # Test maximum
+        a = np.array([1, 2, 3])
+        np.maximum.at(a, [0], 0)
+        assert_equal(a, np.array([1, 2, 3]))
+
+    @pytest.mark.parametrize("dtype",
+            np.typecodes['AllInteger'] + np.typecodes['Float'])
+    @pytest.mark.parametrize("ufunc",
+            [np.add, np.subtract, np.divide, np.minimum, np.maximum])
+    def test_at_negative_indexes(self, dtype, ufunc):
+        a = np.arange(0, 10).astype(dtype)
+        indxs = np.array([-1, 1, -1, 2]).astype(np.intp)
+        vals = np.array([1, 5, 2, 10], dtype=a.dtype)
+
+        expected = a.copy()
+        for i, v in zip(indxs, vals):
+            expected[i] = ufunc(expected[i], v)
+
+        ufunc.at(a, indxs, vals)
+        assert_array_equal(a, expected)
+        assert np.all(indxs == [-1, 1, -1, 2])
+
+    def test_at_not_none_signature(self):
+        # Test ufuncs with non-trivial signature raise a TypeError
+        a = np.ones((2, 2, 2))
+        b = np.ones((1, 2, 2))
+        assert_raises(TypeError, np.matmul.at, a, [0], b)
+
+        a = np.array([[[1, 2], [3, 4]]])
+        assert_raises(TypeError, np.linalg._umath_linalg.det.at, a, [0])
+
+    def test_at_no_loop_for_op(self):
+        # str dtype does not have a ufunc loop for np.add
+        arr = np.ones(10, dtype=str)
+        with pytest.raises(np.core._exceptions._UFuncNoLoopError):
+            np.add.at(arr, [0, 1], [0, 1])
+
+    def test_at_output_casting(self):
+        arr = np.array([-1])
+        np.equal.at(arr, [0], [0])
+        assert arr[0] == 0
+
+    def test_at_broadcast_failure(self):
+        arr = np.arange(5)
+        with pytest.raises(ValueError):
+            np.add.at(arr, [0, 1], [1, 2, 3])
+
+
+    def test_reduce_arguments(self):
+        f = np.add.reduce
+        d = np.ones((5,2), dtype=int)
+        o = np.ones((2,), dtype=d.dtype)
+        r = o * 5
+        assert_equal(f(d), r)
+        # a, axis=0, dtype=None, out=None, keepdims=False
+        assert_equal(f(d, axis=0), r)
+        assert_equal(f(d, 0), r)
+        assert_equal(f(d, 0, dtype=None), r)
+        assert_equal(f(d, 0, dtype='i'), r)
+        assert_equal(f(d, 0, 'i'), r)
+        assert_equal(f(d, 0, None), r)
+        assert_equal(f(d, 0, None, out=None), r)
+        assert_equal(f(d, 0, None, out=o), r)
+        assert_equal(f(d, 0, None, o), r)
+        assert_equal(f(d, 0, None, None), r)
+        assert_equal(f(d, 0, None, None, keepdims=False), r)
+        assert_equal(f(d, 0, None, None, True), r.reshape((1,) + r.shape))
+        assert_equal(f(d, 0, None, None, False, 0), r)
+        assert_equal(f(d, 0, None, None, False, initial=0), r)
+        assert_equal(f(d, 0, None, None, False, 0, True), r)
+        assert_equal(f(d, 0, None, None, False, 0, where=True), r)
+        # multiple keywords
+        assert_equal(f(d, axis=0, dtype=None, out=None, keepdims=False), r)
+        assert_equal(f(d, 0, dtype=None, out=None, keepdims=False), r)
+        assert_equal(f(d, 0, None, out=None, keepdims=False), r)
+        assert_equal(f(d, 0, None, out=None, keepdims=False, initial=0,
+                       where=True), r)
+
+        # too little
+        assert_raises(TypeError, f)
+        # too much
+        assert_raises(TypeError, f, d, 0, None, None, False, 0, True, 1)
+        # invalid axis
+        assert_raises(TypeError, f, d, "invalid")
+        assert_raises(TypeError, f, d, axis="invalid")
+        assert_raises(TypeError, f, d, axis="invalid", dtype=None,
+                      keepdims=True)
+        # invalid dtype
+        assert_raises(TypeError, f, d, 0, "invalid")
+        assert_raises(TypeError, f, d, dtype="invalid")
+        assert_raises(TypeError, f, d, dtype="invalid", out=None)
+        # invalid out
+        assert_raises(TypeError, f, d, 0, None, "invalid")
+        assert_raises(TypeError, f, d, out="invalid")
+        assert_raises(TypeError, f, d, out="invalid", dtype=None)
+        # keepdims boolean, no invalid value
+        # assert_raises(TypeError, f, d, 0, None, None, "invalid")
+        # assert_raises(TypeError, f, d, keepdims="invalid", axis=0, dtype=None)
+        # invalid mix
+        assert_raises(TypeError, f, d, 0, keepdims="invalid", dtype="invalid",
+                     out=None)
+
+        # invalid keyword
+        assert_raises(TypeError, f, d, axis=0, dtype=None, invalid=0)
+        assert_raises(TypeError, f, d, invalid=0)
+        assert_raises(TypeError, f, d, 0, keepdims=True, invalid="invalid",
+                      out=None)
+        assert_raises(TypeError, f, d, axis=0, dtype=None, keepdims=True,
+                      out=None, invalid=0)
+        assert_raises(TypeError, f, d, axis=0, dtype=None,
+                      out=None, invalid=0)
+
+    def test_structured_equal(self):
+        # https://github.com/numpy/numpy/issues/4855
+
+        class MyA(np.ndarray):
+            def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
+                return getattr(ufunc, method)(*(input.view(np.ndarray)
+                                              for input in inputs), **kwargs)
+        a = np.arange(12.).reshape(4,3)
+        ra = a.view(dtype=('f8,f8,f8')).squeeze()
+        mra = ra.view(MyA)
+
+        target = np.array([ True, False, False, False], dtype=bool)
+        assert_equal(np.all(target == (mra == ra[0])), True)
+
+    def test_scalar_equal(self):
+        # Scalar comparisons should always work, without deprecation warnings.
+        # even when the ufunc fails.
+        a = np.array(0.)
+        b = np.array('a')
+        assert_(a != b)
+        assert_(b != a)
+        assert_(not (a == b))
+        assert_(not (b == a))
+
+    def test_NotImplemented_not_returned(self):
+        # See gh-5964 and gh-2091. Some of these functions are not operator
+        # related and were fixed for other reasons in the past.
+        binary_funcs = [
+            np.power, np.add, np.subtract, np.multiply, np.divide,
+            np.true_divide, np.floor_divide, np.bitwise_and, np.bitwise_or,
+            np.bitwise_xor, np.left_shift, np.right_shift, np.fmax,
+            np.fmin, np.fmod, np.hypot, np.logaddexp, np.logaddexp2,
+            np.maximum, np.minimum, np.mod,
+            np.greater, np.greater_equal, np.less, np.less_equal,
+            np.equal, np.not_equal]
+
+        a = np.array('1')
+        b = 1
+        c = np.array([1., 2.])
+        for f in binary_funcs:
+            assert_raises(TypeError, f, a, b)
+            assert_raises(TypeError, f, c, a)
+
+    @pytest.mark.parametrize("ufunc",
+             [np.logical_and, np.logical_or])  # logical_xor object loop is bad
+    @pytest.mark.parametrize("signature",
+             [(None, None, object), (object, None, None),
+              (None, object, None)])
+    def test_logical_ufuncs_object_signatures(self, ufunc, signature):
+        a = np.array([True, None, False], dtype=object)
+        res = ufunc(a, a, signature=signature)
+        assert res.dtype == object
+
+    @pytest.mark.parametrize("ufunc",
+            [np.logical_and, np.logical_or, np.logical_xor])
+    @pytest.mark.parametrize("signature",
+                 [(bool, None, object), (object, None, bool),
+                  (None, object, bool)])
+    def test_logical_ufuncs_mixed_object_signatures(self, ufunc, signature):
+        # Most mixed signatures fail (except those with bool out, e.g. `OO->?`)
+        a = np.array([True, None, False])
+        with pytest.raises(TypeError):
+            ufunc(a, a, signature=signature)
+
+    @pytest.mark.parametrize("ufunc",
+            [np.logical_and, np.logical_or, np.logical_xor])
+    def test_logical_ufuncs_support_anything(self, ufunc):
+        # The logical ufuncs support even input that can't be promoted:
+        a = np.array(b'1', dtype="V3")
+        c = np.array([1., 2.])
+        assert_array_equal(ufunc(a, c), ufunc([True, True], True))
+        assert ufunc.reduce(a) == True
+        # check that the output has no effect:
+        out = np.zeros(2, dtype=np.int32)
+        expected = ufunc([True, True], True).astype(out.dtype)
+        assert_array_equal(ufunc(a, c, out=out), expected)
+        out = np.zeros((), dtype=np.int32)
+        assert ufunc.reduce(a, out=out) == True
+        # Last check, test reduction when out and a match (the complexity here
+        # is that the "i,i->?" may seem right, but should not match.
+        a = np.array([3], dtype="i")
+        out = np.zeros((), dtype=a.dtype)
+        assert ufunc.reduce(a, out=out) == 1
+
+    @pytest.mark.parametrize("ufunc",
+            [np.logical_and, np.logical_or, np.logical_xor])
+    def test_logical_ufuncs_reject_string(self, ufunc):
+        """
+        Logical ufuncs are normally well defined by working with the boolean
+        equivalent, i.e. casting all inputs to bools should work.
+
+        However, casting strings to bools is *currently* weird, because it
+        actually uses `bool(int(str))`.  Thus we explicitly reject strings.
+        This test should succeed (and can probably just be removed) as soon as
+        string to bool casts are well defined in NumPy.
+        """
+        with pytest.raises(TypeError, match="contain a loop with signature"):
+            ufunc(["1"], ["3"])
+        with pytest.raises(TypeError, match="contain a loop with signature"):
+            ufunc.reduce(["1", "2", "0"])
+
+    @pytest.mark.parametrize("ufunc",
+             [np.logical_and, np.logical_or, np.logical_xor])
+    def test_logical_ufuncs_out_cast_check(self, ufunc):
+        a = np.array('1')
+        c = np.array([1., 2.])
+        out = a.copy()
+        with pytest.raises(TypeError):
+            # It would be safe, but not equiv casting:
+            ufunc(a, c, out=out, casting="equiv")
+
+    def test_reducelike_byteorder_resolution(self):
+        # See gh-20699, byte-order changes need some extra care in the type
+        # resolution to make the following succeed:
+        arr_be = np.arange(10, dtype=">i8")
+        arr_le = np.arange(10, dtype="<i8")
+
+        assert np.add.reduce(arr_be) == np.add.reduce(arr_le)
+        assert_array_equal(np.add.accumulate(arr_be), np.add.accumulate(arr_le))
+        assert_array_equal(
+            np.add.reduceat(arr_be, [1]), np.add.reduceat(arr_le, [1]))
+
+    def test_reducelike_out_promotes(self):
+        # Check that the out argument to reductions is considered for
+        # promotion.  See also gh-20455.
+        # Note that these paths could prefer `initial=` in the future and
+        # do not up-cast to the default integer for add and prod
+        arr = np.ones(1000, dtype=np.uint8)
+        out = np.zeros((), dtype=np.uint16)
+        assert np.add.reduce(arr, out=out) == 1000
+        arr[:10] = 2
+        assert np.multiply.reduce(arr, out=out) == 2**10
+
+        # For legacy dtypes, the signature currently has to be forced if `out=`
+        # is passed.  The two paths below should differ, without `dtype=` the
+        # expected result should be: `np.prod(arr.astype("f8")).astype("f4")`!
+        arr = np.full(5, 2**25-1, dtype=np.int64)
+
+        # float32 and int64 promote to float64:
+        res = np.zeros((), dtype=np.float32)
+        # If `dtype=` is passed, the calculation is forced to float32:
+        single_res = np.zeros((), dtype=np.float32)
+        np.multiply.reduce(arr, out=single_res, dtype=np.float32)
+        assert single_res != res
+
+    def test_reducelike_output_needs_identical_cast(self):
+        # Checks the case where the we have a simple byte-swap works, maily
+        # tests that this is not rejected directly.
+        # (interesting because we require descriptor identity in reducelikes).
+        arr = np.ones(20, dtype="f8")
+        out = np.empty((), dtype=arr.dtype.newbyteorder())
+        expected = np.add.reduce(arr)
+        np.add.reduce(arr, out=out)
+        assert_array_equal(expected, out)
+        # Check reduceat:
+        out = np.empty(2, dtype=arr.dtype.newbyteorder())
+        expected = np.add.reduceat(arr, [0, 1])
+        np.add.reduceat(arr, [0, 1], out=out)
+        assert_array_equal(expected, out)
+        # And accumulate:
+        out = np.empty(arr.shape, dtype=arr.dtype.newbyteorder())
+        expected = np.add.accumulate(arr)
+        np.add.accumulate(arr, out=out)
+        assert_array_equal(expected, out)
+
+    def test_reduce_noncontig_output(self):
+        # Check that reduction deals with non-contiguous output arrays
+        # appropriately.
+        #
+        # gh-8036
+
+        x = np.arange(7*13*8, dtype=np.int16).reshape(7, 13, 8)
+        x = x[4:6,1:11:6,1:5].transpose(1, 2, 0)
+        y_base = np.arange(4*4, dtype=np.int16).reshape(4, 4)
+        y = y_base[::2,:]
+
+        y_base_copy = y_base.copy()
+
+        r0 = np.add.reduce(x, out=y.copy(), axis=2)
+        r1 = np.add.reduce(x, out=y, axis=2)
+
+        # The results should match, and y_base shouldn't get clobbered
+        assert_equal(r0, r1)
+        assert_equal(y_base[1,:], y_base_copy[1,:])
+        assert_equal(y_base[3,:], y_base_copy[3,:])
+
+    @pytest.mark.parametrize("with_cast", [True, False])
+    def test_reduceat_and_accumulate_out_shape_mismatch(self, with_cast):
+        # Should raise an error mentioning "shape" or "size"
+        arr = np.arange(5)
+        out = np.arange(3)  # definitely wrong shape
+        if with_cast:
+            # If a cast is necessary on the output, we can be sure to use
+            # the generic NpyIter (non-fast) path.
+            out = out.astype(np.float64)
+
+        with pytest.raises(ValueError, match="(shape|size)"):
+            np.add.reduceat(arr, [0, 3], out=out)
+
+        with pytest.raises(ValueError, match="(shape|size)"):
+            np.add.accumulate(arr, out=out)
+
+    @pytest.mark.parametrize('out_shape',
+                             [(), (1,), (3,), (1, 1), (1, 3), (4, 3)])
+    @pytest.mark.parametrize('keepdims', [True, False])
+    @pytest.mark.parametrize('f_reduce', [np.add.reduce, np.minimum.reduce])
+    def test_reduce_wrong_dimension_output(self, f_reduce, keepdims, out_shape):
+        # Test that we're not incorrectly broadcasting dimensions.
+        # See gh-15144 (failed for np.add.reduce previously).
+        a = np.arange(12.).reshape(4, 3)
+        out = np.empty(out_shape, a.dtype)
+
+        correct_out = f_reduce(a, axis=0, keepdims=keepdims)
+        if out_shape != correct_out.shape:
+            with assert_raises(ValueError):
+                f_reduce(a, axis=0, out=out, keepdims=keepdims)
+        else:
+            check = f_reduce(a, axis=0, out=out, keepdims=keepdims)
+            assert_(check is out)
+            assert_array_equal(check, correct_out)
+
+    def test_reduce_output_does_not_broadcast_input(self):
+        # Test that the output shape cannot broadcast an input dimension
+        # (it never can add dimensions, but it might expand an existing one)
+        a = np.ones((1, 10))
+        out_correct = (np.empty((1, 1)))
+        out_incorrect = np.empty((3, 1))
+        np.add.reduce(a, axis=-1, out=out_correct, keepdims=True)
+        np.add.reduce(a, axis=-1, out=out_correct[:, 0], keepdims=False)
+        with assert_raises(ValueError):
+            np.add.reduce(a, axis=-1, out=out_incorrect, keepdims=True)
+        with assert_raises(ValueError):
+            np.add.reduce(a, axis=-1, out=out_incorrect[:, 0], keepdims=False)
+
+    def test_reduce_output_subclass_ok(self):
+        class MyArr(np.ndarray):
+            pass
+
+        out = np.empty(())
+        np.add.reduce(np.ones(5), out=out)  # no subclass, all fine
+        out = out.view(MyArr)
+        assert np.add.reduce(np.ones(5), out=out) is out
+        assert type(np.add.reduce(out)) is MyArr
+
+    def test_no_doc_string(self):
+        # gh-9337
+        assert_('\n' not in umt.inner1d_no_doc.__doc__)
+
+    def test_invalid_args(self):
+        # gh-7961
+        exc = pytest.raises(TypeError, np.sqrt, None)
+        # minimally check the exception text
+        assert exc.match('loop of ufunc does not support')
+
+    @pytest.mark.parametrize('nat', [np.datetime64('nat'), np.timedelta64('nat')])
+    def test_nat_is_not_finite(self, nat):
+        try:
+            assert not np.isfinite(nat)
+        except TypeError:
+            pass  # ok, just not implemented
+
+    @pytest.mark.parametrize('nat', [np.datetime64('nat'), np.timedelta64('nat')])
+    def test_nat_is_nan(self, nat):
+        try:
+            assert np.isnan(nat)
+        except TypeError:
+            pass  # ok, just not implemented
+
+    @pytest.mark.parametrize('nat', [np.datetime64('nat'), np.timedelta64('nat')])
+    def test_nat_is_not_inf(self, nat):
+        try:
+            assert not np.isinf(nat)
+        except TypeError:
+            pass  # ok, just not implemented
+
+
+@pytest.mark.parametrize('ufunc', [getattr(np, x) for x in dir(np)
+                                if isinstance(getattr(np, x), np.ufunc)])
+def test_ufunc_types(ufunc):
+    '''
+    Check all ufuncs that the correct type is returned. Avoid
+    object and boolean types since many operations are not defined for
+    for them.
+
+    Choose the shape so even dot and matmul will succeed
+    '''
+    for typ in ufunc.types:
+        # types is a list of strings like ii->i
+        if 'O' in typ or '?' in typ:
+            continue
+        inp, out = typ.split('->')
+        args = [np.ones((3, 3), t) for t in inp]
+        with warnings.catch_warnings(record=True):
+            warnings.filterwarnings("always")
+            res = ufunc(*args)
+        if isinstance(res, tuple):
+            outs = tuple(out)
+            assert len(res) == len(outs)
+            for r, t in zip(res, outs):
+                assert r.dtype == np.dtype(t)
+        else:
+            assert res.dtype == np.dtype(out)
+
+@pytest.mark.parametrize('ufunc', [getattr(np, x) for x in dir(np)
+                                if isinstance(getattr(np, x), np.ufunc)])
+@np._no_nep50_warning()
+def test_ufunc_noncontiguous(ufunc):
+    '''
+    Check that contiguous and non-contiguous calls to ufuncs
+    have the same results for values in range(9)
+    '''
+    for typ in ufunc.types:
+        # types is a list of strings like ii->i
+        if any(set('O?mM') & set(typ)):
+            # bool, object, datetime are too irregular for this simple test
+            continue
+        inp, out = typ.split('->')
+        args_c = [np.empty(6, t) for t in inp]
+        args_n = [np.empty(18, t)[::3] for t in inp]
+        for a in args_c:
+            a.flat = range(1,7)
+        for a in args_n:
+            a.flat = range(1,7)
+        with warnings.catch_warnings(record=True):
+            warnings.filterwarnings("always")
+            res_c = ufunc(*args_c)
+            res_n = ufunc(*args_n)
+        if len(out) == 1:
+            res_c = (res_c,)
+            res_n = (res_n,)
+        for c_ar, n_ar in zip(res_c, res_n):
+            dt = c_ar.dtype
+            if np.issubdtype(dt, np.floating):
+                # for floating point results allow a small fuss in comparisons
+                # since different algorithms (libm vs. intrinsics) can be used
+                # for different input strides
+                res_eps = np.finfo(dt).eps
+                tol = 2*res_eps
+                assert_allclose(res_c, res_n, atol=tol, rtol=tol)
+            else:
+                assert_equal(c_ar, n_ar)
+
+
+@pytest.mark.parametrize('ufunc', [np.sign, np.equal])
+def test_ufunc_warn_with_nan(ufunc):
+    # issue gh-15127
+    # test that calling certain ufuncs with a non-standard `nan` value does not
+    # emit a warning
+    # `b` holds a 64 bit signaling nan: the most significant bit of the
+    # significand is zero.
+    b = np.array([0x7ff0000000000001], 'i8').view('f8')
+    assert np.isnan(b)
+    if ufunc.nin == 1:
+        ufunc(b)
+    elif ufunc.nin == 2:
+        ufunc(b, b.copy())
+    else:
+        raise ValueError('ufunc with more than 2 inputs')
+
+
+@pytest.mark.skipif(not HAS_REFCOUNT, reason="Python lacks refcounts")
+def test_ufunc_out_casterrors():
+    # Tests that casting errors are correctly reported and buffers are
+    # cleared.
+    # The following array can be added to itself as an object array, but
+    # the result cannot be cast to an integer output:
+    value = 123  # relies on python cache (leak-check will still find it)
+    arr = np.array([value] * int(np.BUFSIZE * 1.5) +
+                   ["string"] +
+                   [value] * int(1.5 * np.BUFSIZE), dtype=object)
+    out = np.ones(len(arr), dtype=np.intp)
+
+    count = sys.getrefcount(value)
+    with pytest.raises(ValueError):
+        # Output casting failure:
+        np.add(arr, arr, out=out, casting="unsafe")
+
+    assert count == sys.getrefcount(value)
+    # output is unchanged after the error, this shows that the iteration
+    # was aborted (this is not necessarily defined behaviour)
+    assert out[-1] == 1
+
+    with pytest.raises(ValueError):
+        # Input casting failure:
+        np.add(arr, arr, out=out, dtype=np.intp, casting="unsafe")
+
+    assert count == sys.getrefcount(value)
+    # output is unchanged after the error, this shows that the iteration
+    # was aborted (this is not necessarily defined behaviour)
+    assert out[-1] == 1
+
+
+@pytest.mark.parametrize("bad_offset", [0, int(np.BUFSIZE * 1.5)])
+def test_ufunc_input_casterrors(bad_offset):
+    value = 123
+    arr = np.array([value] * bad_offset +
+                   ["string"] +
+                   [value] * int(1.5 * np.BUFSIZE), dtype=object)
+    with pytest.raises(ValueError):
+        # Force cast inputs, but the buffered cast of `arr` to intp fails:
+        np.add(arr, arr, dtype=np.intp, casting="unsafe")
+
+
+@pytest.mark.skipif(IS_WASM, reason="fp errors don't work in wasm")
+@pytest.mark.parametrize("bad_offset", [0, int(np.BUFSIZE * 1.5)])
+def test_ufunc_input_floatingpoint_error(bad_offset):
+    value = 123
+    arr = np.array([value] * bad_offset +
+                   [np.nan] +
+                   [value] * int(1.5 * np.BUFSIZE))
+    with np.errstate(invalid="raise"), pytest.raises(FloatingPointError):
+        # Force cast inputs, but the buffered cast of `arr` to intp fails:
+        np.add(arr, arr, dtype=np.intp, casting="unsafe")
+
+
+def test_trivial_loop_invalid_cast():
+    # This tests the fast-path "invalid cast", see gh-19904.
+    with pytest.raises(TypeError,
+            match="cast ufunc 'add' input 0"):
+        # the void dtype definitely cannot cast to double:
+        np.add(np.array(1, "i,i"), 3, signature="dd->d")
+
+
+@pytest.mark.skipif(not HAS_REFCOUNT, reason="Python lacks refcounts")
+@pytest.mark.parametrize("offset",
+        [0, np.BUFSIZE//2, int(1.5*np.BUFSIZE)])
+def test_reduce_casterrors(offset):
+    # Test reporting of casting errors in reductions, we test various
+    # offsets to where the casting error will occur, since these may occur
+    # at different places during the reduction procedure. For example
+    # the first item may be special.
+    value = 123  # relies on python cache (leak-check will still find it)
+    arr = np.array([value] * offset +
+                   ["string"] +
+                   [value] * int(1.5 * np.BUFSIZE), dtype=object)
+    out = np.array(-1, dtype=np.intp)
+
+    count = sys.getrefcount(value)
+    with pytest.raises(ValueError, match="invalid literal"):
+        # This is an unsafe cast, but we currently always allow that.
+        # Note that the double loop is picked, but the cast fails.
+        # `initial=None` disables the use of an identity here to test failures
+        # while copying the first values path (not used when identity exists).
+        np.add.reduce(arr, dtype=np.intp, out=out, initial=None)
+    assert count == sys.getrefcount(value)
+    # If an error occurred during casting, the operation is done at most until
+    # the error occurs (the result of which would be `value * offset`) and -1
+    # if the error happened immediately.
+    # This does not define behaviour, the output is invalid and thus undefined
+    assert out[()] < value * offset
+
+
+def test_object_reduce_cleanup_on_failure():
+    # Test cleanup, including of the initial value (manually provided or not)
+    with pytest.raises(TypeError):
+        np.add.reduce([1, 2, None], initial=4)
+
+    with pytest.raises(TypeError):
+        np.add.reduce([1, 2, None])
+
+
+@pytest.mark.skipif(IS_WASM, reason="fp errors don't work in wasm")
+@pytest.mark.parametrize("method",
+        [np.add.accumulate, np.add.reduce,
+         pytest.param(lambda x: np.add.reduceat(x, [0]), id="reduceat"),
+         pytest.param(lambda x: np.log.at(x, [2]), id="at")])
+def test_ufunc_methods_floaterrors(method):
+    # adding inf and -inf (or log(-inf) creates an invalid float and warns
+    arr = np.array([np.inf, 0, -np.inf])
+    with np.errstate(all="warn"):
+        with pytest.warns(RuntimeWarning, match="invalid value"):
+            method(arr)
+
+    arr = np.array([np.inf, 0, -np.inf])
+    with np.errstate(all="raise"):
+        with pytest.raises(FloatingPointError):
+            method(arr)
+
+
+def _check_neg_zero(value):
+    if value != 0.0:
+        return False
+    if not np.signbit(value.real):
+        return False
+    if value.dtype.kind == "c":
+        return np.signbit(value.imag)
+    return True
+
+@pytest.mark.parametrize("dtype", np.typecodes["AllFloat"])
+def test_addition_negative_zero(dtype):
+    dtype = np.dtype(dtype)
+    if dtype.kind == "c":
+        neg_zero = dtype.type(complex(-0.0, -0.0))
+    else:
+        neg_zero = dtype.type(-0.0)
+
+    arr = np.array(neg_zero)
+    arr2 = np.array(neg_zero)
+
+    assert _check_neg_zero(arr + arr2)
+    # In-place ops may end up on a different path (reduce path) see gh-21211
+    arr += arr2
+    assert _check_neg_zero(arr)
+
+
+@pytest.mark.parametrize("dtype", np.typecodes["AllFloat"])
+@pytest.mark.parametrize("use_initial", [True, False])
+def test_addition_reduce_negative_zero(dtype, use_initial):
+    dtype = np.dtype(dtype)
+    if dtype.kind == "c":
+        neg_zero = dtype.type(complex(-0.0, -0.0))
+    else:
+        neg_zero = dtype.type(-0.0)
+
+    kwargs = {}
+    if use_initial:
+        kwargs["initial"] = neg_zero
+    else:
+        pytest.xfail("-0. propagation in sum currently requires initial")
+
+    # Test various length, in case SIMD paths or chunking play a role.
+    # 150 extends beyond the pairwise blocksize; probably not important.
+    for i in range(0, 150):
+        arr = np.array([neg_zero] * i, dtype=dtype)
+        res = np.sum(arr, **kwargs)
+        if i > 0 or use_initial:
+            assert _check_neg_zero(res)
+        else:
+            # `sum([])` should probably be 0.0 and not -0.0 like `sum([-0.0])`
+            assert not np.signbit(res.real)
+            assert not np.signbit(res.imag)
+
+class TestLowlevelAPIAccess:
+    def test_resolve_dtypes_basic(self):
+        # Basic test for dtype resolution:
+        i4 = np.dtype("i4")
+        f4 = np.dtype("f4")
+        f8 = np.dtype("f8")
+
+        r = np.add.resolve_dtypes((i4, f4, None))
+        assert r == (f8, f8, f8)
+
+        # Signature uses the same logic to parse as ufunc (less strict)
+        # the following is "same-kind" casting so works:
+        r = np.add.resolve_dtypes((
+                i4, i4, None), signature=(None, None, "f4"))
+        assert r == (f4, f4, f4)
+
+        # Check NEP 50 "weak" promotion also:
+        r = np.add.resolve_dtypes((f4, int, None))
+        assert r == (f4, f4, f4)
+
+        with pytest.raises(TypeError):
+            np.add.resolve_dtypes((i4, f4, None), casting="no")
+
+    def test_weird_dtypes(self):
+        S0 = np.dtype("S0")
+        # S0 is often converted by NumPy to S1, but not here:
+        r = np.equal.resolve_dtypes((S0, S0, None))
+        assert r == (S0, S0, np.dtype(bool))
+
+        # Subarray dtypes are weird and may not work fully, we preserve them
+        # leading to a TypeError (currently no equal loop for void/structured)
+        dts = np.dtype("10i")
+        with pytest.raises(TypeError):
+            np.equal.resolve_dtypes((dts, dts, None))
+
+    def test_resolve_dtypes_reduction(self):
+        i4 = np.dtype("i4")
+        with pytest.raises(NotImplementedError):
+            np.add.resolve_dtypes((i4, i4, i4), reduction=True)
+
+    @pytest.mark.parametrize("dtypes", [
+            (np.dtype("i"), np.dtype("i")),
+            (None, np.dtype("i"), np.dtype("f")),
+            (np.dtype("i"), None, np.dtype("f")),
+            ("i4", "i4", None)])
+    def test_resolve_dtypes_errors(self, dtypes):
+        with pytest.raises(TypeError):
+            np.add.resolve_dtypes(dtypes)
+
+    def test_resolve_dtypes_reduction(self):
+        i2 = np.dtype("i2")
+        long_ = np.dtype("long")
+        # Check special addition resolution:
+        res = np.add.resolve_dtypes((None, i2, None), reduction=True)
+        assert res == (long_, long_, long_)
+
+    def test_resolve_dtypes_reduction_errors(self):
+        i2 = np.dtype("i2")
+
+        with pytest.raises(TypeError):
+            np.add.resolve_dtypes((None, i2, i2))
+
+        with pytest.raises(TypeError):
+            np.add.signature((None, None, "i4"))
+
+    @pytest.mark.skipif(not hasattr(ct, "pythonapi"),
+            reason="`ctypes.pythonapi` required for capsule unpacking.")
+    def test_loop_access(self):
+        # This is a basic test for the full strided loop access
+        data_t = ct.ARRAY(ct.c_char_p, 2)
+        dim_t = ct.ARRAY(ct.c_ssize_t, 1)
+        strides_t = ct.ARRAY(ct.c_ssize_t, 2)
+        strided_loop_t = ct.CFUNCTYPE(
+                ct.c_int, ct.c_void_p, data_t, dim_t, strides_t, ct.c_void_p)
+
+        class call_info_t(ct.Structure):
+            _fields_ = [
+                ("strided_loop", strided_loop_t),
+                ("context", ct.c_void_p),
+                ("auxdata", ct.c_void_p),
+                ("requires_pyapi", ct.c_byte),
+                ("no_floatingpoint_errors", ct.c_byte),
+            ]
+
+        i4 = np.dtype("i4")
+        dt, call_info_obj = np.negative._resolve_dtypes_and_context((i4, i4))
+        assert dt == (i4, i4)  # can be used without casting
+
+        # Fill in the rest of the information:
+        np.negative._get_strided_loop(call_info_obj)
+
+        ct.pythonapi.PyCapsule_GetPointer.restype = ct.c_void_p
+        call_info = ct.pythonapi.PyCapsule_GetPointer(
+                ct.py_object(call_info_obj),
+                ct.c_char_p(b"numpy_1.24_ufunc_call_info"))
+
+        call_info = ct.cast(call_info, ct.POINTER(call_info_t)).contents
+
+        arr = np.arange(10, dtype=i4)
+        call_info.strided_loop(
+                call_info.context,
+                data_t(arr.ctypes.data, arr.ctypes.data),
+                arr.ctypes.shape,  # is a C-array with 10 here
+                strides_t(arr.ctypes.strides[0], arr.ctypes.strides[0]),
+                call_info.auxdata)
+
+        # We just directly called the negative inner-loop in-place:
+        assert_array_equal(arr, -np.arange(10, dtype=i4))
+
+    @pytest.mark.parametrize("strides", [1, (1, 2, 3), (1, "2")])
+    def test__get_strided_loop_errors_bad_strides(self, strides):
+        i4 = np.dtype("i4")
+        dt, call_info = np.negative._resolve_dtypes_and_context((i4, i4))
+
+        with pytest.raises(TypeError, match="fixed_strides.*tuple.*or None"):
+            np.negative._get_strided_loop(call_info, fixed_strides=strides)
+
+    def test__get_strided_loop_errors_bad_call_info(self):
+        i4 = np.dtype("i4")
+        dt, call_info = np.negative._resolve_dtypes_and_context((i4, i4))
+
+        with pytest.raises(ValueError, match="PyCapsule"):
+            np.negative._get_strided_loop("not the capsule!")
+
+        with pytest.raises(TypeError, match=".*incompatible context"):
+            np.add._get_strided_loop(call_info)
+
+        np.negative._get_strided_loop(call_info)
+        with pytest.raises(TypeError):
+            # cannot call it a second time:
+            np.negative._get_strided_loop(call_info)
+
+    def test_long_arrays(self):
+        t = np.zeros((1029, 917), dtype=np.single)
+        t[0][0] = 1
+        t[28][414] = 1
+        tc = np.cos(t)
+        assert_equal(tc[0][0], tc[28][414])