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b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/gw1.gpickle.bz2 diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/netgen-2.gpickle.bz2 b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/netgen-2.gpickle.bz2 Binary files differnew file mode 100644 index 00000000..cd3ea801 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/netgen-2.gpickle.bz2 diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_gomory_hu.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_gomory_hu.py new file mode 100644 index 00000000..1649ec82 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_gomory_hu.py @@ -0,0 +1,128 @@ +from itertools import combinations + +import pytest + +import networkx as nx +from networkx.algorithms.flow import ( + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +) + +flow_funcs = [ + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +] + + +class TestGomoryHuTree: + def minimum_edge_weight(self, T, u, v): + path = nx.shortest_path(T, u, v, weight="weight") + return min((T[u][v]["weight"], (u, v)) for (u, v) in zip(path, path[1:])) + + def compute_cutset(self, G, T_orig, edge): + T = T_orig.copy() + T.remove_edge(*edge) + U, V = list(nx.connected_components(T)) + cutset = set() + for x, nbrs in ((n, G[n]) for n in U): + cutset.update((x, y) for y in nbrs if y in V) + return cutset + + def test_default_flow_function_karate_club_graph(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + T = nx.gomory_hu_tree(G) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_karate_club_graph(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_davis_southern_women_graph(self): + G = nx.davis_southern_women_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_florentine_families_graph(self): + G = nx.florentine_families_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + @pytest.mark.slow + def test_les_miserables_graph_cutset(self): + G = nx.les_miserables_graph() + nx.set_edge_attributes(G, 1, "capacity") + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v) == cut_value + + def test_karate_club_graph_cutset(self): + G = nx.karate_club_graph() + nx.set_edge_attributes(G, 1, "capacity") + T = nx.gomory_hu_tree(G) + assert nx.is_tree(T) + u, v = 0, 33 + cut_value, edge = self.minimum_edge_weight(T, u, v) + cutset = self.compute_cutset(G, T, edge) + assert cut_value == len(cutset) + + def test_wikipedia_example(self): + # Example from https://en.wikipedia.org/wiki/Gomory%E2%80%93Hu_tree + G = nx.Graph() + G.add_weighted_edges_from( + ( + (0, 1, 1), + (0, 2, 7), + (1, 2, 1), + (1, 3, 3), + (1, 4, 2), + (2, 4, 4), + (3, 4, 1), + (3, 5, 6), + (4, 5, 2), + ) + ) + for flow_func in flow_funcs: + T = nx.gomory_hu_tree(G, capacity="weight", flow_func=flow_func) + assert nx.is_tree(T) + for u, v in combinations(G, 2): + cut_value, edge = self.minimum_edge_weight(T, u, v) + assert nx.minimum_cut_value(G, u, v, capacity="weight") == cut_value + + def test_directed_raises(self): + with pytest.raises(nx.NetworkXNotImplemented): + G = nx.DiGraph() + T = nx.gomory_hu_tree(G) + + def test_empty_raises(self): + with pytest.raises(nx.NetworkXError): + G = nx.empty_graph() + T = nx.gomory_hu_tree(G) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow.py new file mode 100644 index 00000000..d7305a7b --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow.py @@ -0,0 +1,573 @@ +"""Maximum flow algorithms test suite.""" + +import pytest + +import networkx as nx +from networkx.algorithms.flow import ( + boykov_kolmogorov, + build_flow_dict, + build_residual_network, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +) + +flow_funcs = { + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +} + +max_min_funcs = {nx.maximum_flow, nx.minimum_cut} +flow_value_funcs = {nx.maximum_flow_value, nx.minimum_cut_value} +interface_funcs = max_min_funcs | flow_value_funcs +all_funcs = flow_funcs | interface_funcs + + +def compute_cutset(G, partition): + reachable, non_reachable = partition + cutset = set() + for u, nbrs in ((n, G[n]) for n in reachable): + cutset.update((u, v) for v in nbrs if v in non_reachable) + return cutset + + +def validate_flows(G, s, t, flowDict, solnValue, capacity, flow_func): + errmsg = f"Assertion failed in function: {flow_func.__name__}" + assert set(G) == set(flowDict), errmsg + for u in G: + assert set(G[u]) == set(flowDict[u]), errmsg + excess = {u: 0 for u in flowDict} + for u in flowDict: + for v, flow in flowDict[u].items(): + if capacity in G[u][v]: + assert flow <= G[u][v][capacity] + assert flow >= 0, errmsg + excess[u] -= flow + excess[v] += flow + for u, exc in excess.items(): + if u == s: + assert exc == -solnValue, errmsg + elif u == t: + assert exc == solnValue, errmsg + else: + assert exc == 0, errmsg + + +def validate_cuts(G, s, t, solnValue, partition, capacity, flow_func): + errmsg = f"Assertion failed in function: {flow_func.__name__}" + assert all(n in G for n in partition[0]), errmsg + assert all(n in G for n in partition[1]), errmsg + cutset = compute_cutset(G, partition) + assert all(G.has_edge(u, v) for (u, v) in cutset), errmsg + assert solnValue == sum(G[u][v][capacity] for (u, v) in cutset), errmsg + H = G.copy() + H.remove_edges_from(cutset) + if not G.is_directed(): + assert not nx.is_connected(H), errmsg + else: + assert not nx.is_strongly_connected(H), errmsg + + +def compare_flows_and_cuts(G, s, t, solnValue, capacity="capacity"): + for flow_func in flow_funcs: + errmsg = f"Assertion failed in function: {flow_func.__name__}" + R = flow_func(G, s, t, capacity) + # Test both legacy and new implementations. + flow_value = R.graph["flow_value"] + flow_dict = build_flow_dict(G, R) + assert flow_value == solnValue, errmsg + validate_flows(G, s, t, flow_dict, solnValue, capacity, flow_func) + # Minimum cut + cut_value, partition = nx.minimum_cut( + G, s, t, capacity=capacity, flow_func=flow_func + ) + validate_cuts(G, s, t, solnValue, partition, capacity, flow_func) + + +class TestMaxflowMinCutCommon: + def test_graph1(self): + # Trivial undirected graph + G = nx.Graph() + G.add_edge(1, 2, capacity=1.0) + + # solution flows + # {1: {2: 1.0}, 2: {1: 1.0}} + + compare_flows_and_cuts(G, 1, 2, 1.0) + + def test_graph2(self): + # A more complex undirected graph + # adapted from https://web.archive.org/web/20220815055650/https://www.topcoder.com/thrive/articles/Maximum%20Flow:%20Part%20One + G = nx.Graph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + + # H + # { + # "x": {"a": 3, "b": 1}, + # "a": {"c": 3, "x": 3}, + # "b": {"c": 1, "d": 2, "x": 1}, + # "c": {"a": 3, "b": 1, "y": 2}, + # "d": {"b": 2, "e": 2}, + # "e": {"d": 2, "y": 2}, + # "y": {"c": 2, "e": 2}, + # } + + compare_flows_and_cuts(G, "x", "y", 4.0) + + def test_digraph1(self): + # The classic directed graph example + G = nx.DiGraph() + G.add_edge("a", "b", capacity=1000.0) + G.add_edge("a", "c", capacity=1000.0) + G.add_edge("b", "c", capacity=1.0) + G.add_edge("b", "d", capacity=1000.0) + G.add_edge("c", "d", capacity=1000.0) + + # H + # { + # "a": {"b": 1000.0, "c": 1000.0}, + # "b": {"c": 0, "d": 1000.0}, + # "c": {"d": 1000.0}, + # "d": {}, + # } + + compare_flows_and_cuts(G, "a", "d", 2000.0) + + def test_digraph2(self): + # An example in which some edges end up with zero flow. + G = nx.DiGraph() + G.add_edge("s", "b", capacity=2) + G.add_edge("s", "c", capacity=1) + G.add_edge("c", "d", capacity=1) + G.add_edge("d", "a", capacity=1) + G.add_edge("b", "a", capacity=2) + G.add_edge("a", "t", capacity=2) + + # H + # { + # "s": {"b": 2, "c": 0}, + # "c": {"d": 0}, + # "d": {"a": 0}, + # "b": {"a": 2}, + # "a": {"t": 2}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 2) + + def test_digraph3(self): + # A directed graph example from Cormen et al. + G = nx.DiGraph() + G.add_edge("s", "v1", capacity=16.0) + G.add_edge("s", "v2", capacity=13.0) + G.add_edge("v1", "v2", capacity=10.0) + G.add_edge("v2", "v1", capacity=4.0) + G.add_edge("v1", "v3", capacity=12.0) + G.add_edge("v3", "v2", capacity=9.0) + G.add_edge("v2", "v4", capacity=14.0) + G.add_edge("v4", "v3", capacity=7.0) + G.add_edge("v3", "t", capacity=20.0) + G.add_edge("v4", "t", capacity=4.0) + + # H + # { + # "s": {"v1": 12.0, "v2": 11.0}, + # "v2": {"v1": 0, "v4": 11.0}, + # "v1": {"v2": 0, "v3": 12.0}, + # "v3": {"v2": 0, "t": 19.0}, + # "v4": {"v3": 7.0, "t": 4.0}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 23.0) + + def test_digraph4(self): + # A more complex directed graph + # from https://web.archive.org/web/20220815055650/https://www.topcoder.com/thrive/articles/Maximum%20Flow:%20Part%20One + G = nx.DiGraph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + + # H + # { + # "x": {"a": 2.0, "b": 1.0}, + # "a": {"c": 2.0}, + # "b": {"c": 0, "d": 1.0}, + # "c": {"y": 2.0}, + # "d": {"e": 1.0}, + # "e": {"y": 1.0}, + # "y": {}, + # } + + compare_flows_and_cuts(G, "x", "y", 3.0) + + def test_wikipedia_dinitz_example(self): + # Nice example from https://en.wikipedia.org/wiki/Dinic's_algorithm + G = nx.DiGraph() + G.add_edge("s", 1, capacity=10) + G.add_edge("s", 2, capacity=10) + G.add_edge(1, 3, capacity=4) + G.add_edge(1, 4, capacity=8) + G.add_edge(1, 2, capacity=2) + G.add_edge(2, 4, capacity=9) + G.add_edge(3, "t", capacity=10) + G.add_edge(4, 3, capacity=6) + G.add_edge(4, "t", capacity=10) + + # solution flows + # { + # 1: {2: 0, 3: 4, 4: 6}, + # 2: {4: 9}, + # 3: {"t": 9}, + # 4: {3: 5, "t": 10}, + # "s": {1: 10, 2: 9}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 19) + + def test_optional_capacity(self): + # Test optional capacity parameter. + G = nx.DiGraph() + G.add_edge("x", "a", spam=3.0) + G.add_edge("x", "b", spam=1.0) + G.add_edge("a", "c", spam=3.0) + G.add_edge("b", "c", spam=5.0) + G.add_edge("b", "d", spam=4.0) + G.add_edge("d", "e", spam=2.0) + G.add_edge("c", "y", spam=2.0) + G.add_edge("e", "y", spam=3.0) + + # solution flows + # { + # "x": {"a": 2.0, "b": 1.0}, + # "a": {"c": 2.0}, + # "b": {"c": 0, "d": 1.0}, + # "c": {"y": 2.0}, + # "d": {"e": 1.0}, + # "e": {"y": 1.0}, + # "y": {}, + # } + solnValue = 3.0 + s = "x" + t = "y" + + compare_flows_and_cuts(G, s, t, solnValue, capacity="spam") + + def test_digraph_infcap_edges(self): + # DiGraph with infinite capacity edges + G = nx.DiGraph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c", capacity=25) + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "t": 60}, + # "b": {"c": 12}, + # "c": {"t": 37}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + # DiGraph with infinite capacity digon + G = nx.DiGraph() + G.add_edge("s", "a", capacity=85) + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c") + G.add_edge("c", "a") + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t", capacity=37) + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "t": 60}, + # "c": {"a": 0, "t": 37}, + # "b": {"c": 12}, + # "t": {}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + def test_digraph_infcap_path(self): + # Graph with infinite capacity (s, t)-path + G = nx.DiGraph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c") + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + for flow_func in all_funcs: + pytest.raises(nx.NetworkXUnbounded, flow_func, G, "s", "t") + + def test_graph_infcap_edges(self): + # Undirected graph with infinite capacity edges + G = nx.Graph() + G.add_edge("s", "a") + G.add_edge("s", "b", capacity=30) + G.add_edge("a", "c", capacity=25) + G.add_edge("b", "c", capacity=12) + G.add_edge("a", "t", capacity=60) + G.add_edge("c", "t") + + # H + # { + # "s": {"a": 85, "b": 12}, + # "a": {"c": 25, "s": 85, "t": 60}, + # "b": {"c": 12, "s": 12}, + # "c": {"a": 25, "b": 12, "t": 37}, + # "t": {"a": 60, "c": 37}, + # } + + compare_flows_and_cuts(G, "s", "t", 97) + + def test_digraph5(self): + # From ticket #429 by mfrasca. + G = nx.DiGraph() + G.add_edge("s", "a", capacity=2) + G.add_edge("s", "b", capacity=2) + G.add_edge("a", "b", capacity=5) + G.add_edge("a", "t", capacity=1) + G.add_edge("b", "a", capacity=1) + G.add_edge("b", "t", capacity=3) + # flow solution + # { + # "a": {"b": 1, "t": 1}, + # "b": {"a": 0, "t": 3}, + # "s": {"a": 2, "b": 2}, + # "t": {}, + # } + compare_flows_and_cuts(G, "s", "t", 4) + + def test_disconnected(self): + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(1) + assert nx.maximum_flow_value(G, 0, 3) == 0 + # flow solution + # {0: {}, 2: {3: 0}, 3: {2: 0}} + compare_flows_and_cuts(G, 0, 3, 0) + + def test_source_target_not_in_graph(self): + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(0) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 3) + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + G.remove_node(3) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 3) + + def test_source_target_coincide(self): + G = nx.Graph() + G.add_node(0) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 0) + + def test_multigraphs_raise(self): + G = nx.MultiGraph() + M = nx.MultiDiGraph() + G.add_edges_from([(0, 1), (1, 0)], capacity=True) + for flow_func in all_funcs: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 0) + + +class TestMaxFlowMinCutInterface: + def setup_method(self): + G = nx.DiGraph() + G.add_edge("x", "a", capacity=3.0) + G.add_edge("x", "b", capacity=1.0) + G.add_edge("a", "c", capacity=3.0) + G.add_edge("b", "c", capacity=5.0) + G.add_edge("b", "d", capacity=4.0) + G.add_edge("d", "e", capacity=2.0) + G.add_edge("c", "y", capacity=2.0) + G.add_edge("e", "y", capacity=3.0) + self.G = G + H = nx.DiGraph() + H.add_edge(0, 1, capacity=1.0) + H.add_edge(1, 2, capacity=1.0) + self.H = H + + def test_flow_func_not_callable(self): + elements = ["this_should_be_callable", 10, {1, 2, 3}] + G = nx.Graph() + G.add_weighted_edges_from([(0, 1, 1), (1, 2, 1), (2, 3, 1)], weight="capacity") + for flow_func in interface_funcs: + for element in elements: + pytest.raises(nx.NetworkXError, flow_func, G, 0, 1, flow_func=element) + pytest.raises(nx.NetworkXError, flow_func, G, 0, 1, flow_func=element) + + def test_flow_func_parameters(self): + G = self.G + fv = 3.0 + for interface_func in interface_funcs: + for flow_func in flow_funcs: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + result = interface_func(G, "x", "y", flow_func=flow_func) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + def test_minimum_cut_no_cutoff(self): + G = self.G + pytest.raises( + nx.NetworkXError, + nx.minimum_cut, + G, + "x", + "y", + flow_func=preflow_push, + cutoff=1.0, + ) + pytest.raises( + nx.NetworkXError, + nx.minimum_cut_value, + G, + "x", + "y", + flow_func=preflow_push, + cutoff=1.0, + ) + + def test_kwargs(self): + G = self.H + fv = 1.0 + to_test = ( + (shortest_augmenting_path, {"two_phase": True}), + (preflow_push, {"global_relabel_freq": 5}), + ) + for interface_func in interface_funcs: + for flow_func, kwargs in to_test: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + result = interface_func(G, 0, 2, flow_func=flow_func, **kwargs) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + def test_kwargs_default_flow_func(self): + G = self.H + for interface_func in interface_funcs: + pytest.raises( + nx.NetworkXError, interface_func, G, 0, 1, global_relabel_freq=2 + ) + + def test_reusing_residual(self): + G = self.G + fv = 3.0 + s, t = "x", "y" + R = build_residual_network(G, "capacity") + for interface_func in interface_funcs: + for flow_func in flow_funcs: + errmsg = ( + f"Assertion failed in function: {flow_func.__name__} " + f"in interface {interface_func.__name__}" + ) + for i in range(3): + result = interface_func( + G, "x", "y", flow_func=flow_func, residual=R + ) + if interface_func in max_min_funcs: + result = result[0] + assert fv == result, errmsg + + +# Tests specific to one algorithm +def test_preflow_push_global_relabel_freq(): + G = nx.DiGraph() + G.add_edge(1, 2, capacity=1) + R = preflow_push(G, 1, 2, global_relabel_freq=None) + assert R.graph["flow_value"] == 1 + pytest.raises(nx.NetworkXError, preflow_push, G, 1, 2, global_relabel_freq=-1) + + +def test_preflow_push_makes_enough_space(): + # From ticket #1542 + G = nx.DiGraph() + nx.add_path(G, [0, 1, 3], capacity=1) + nx.add_path(G, [1, 2, 3], capacity=1) + R = preflow_push(G, 0, 3, value_only=False) + assert R.graph["flow_value"] == 1 + + +def test_shortest_augmenting_path_two_phase(): + k = 5 + p = 1000 + G = nx.DiGraph() + for i in range(k): + G.add_edge("s", (i, 0), capacity=1) + nx.add_path(G, ((i, j) for j in range(p)), capacity=1) + G.add_edge((i, p - 1), "t", capacity=1) + R = shortest_augmenting_path(G, "s", "t", two_phase=True) + assert R.graph["flow_value"] == k + R = shortest_augmenting_path(G, "s", "t", two_phase=False) + assert R.graph["flow_value"] == k + + +class TestCutoff: + def test_cutoff(self): + k = 5 + p = 1000 + G = nx.DiGraph() + for i in range(k): + G.add_edge("s", (i, 0), capacity=2) + nx.add_path(G, ((i, j) for j in range(p)), capacity=2) + G.add_edge((i, p - 1), "t", capacity=2) + R = shortest_augmenting_path(G, "s", "t", two_phase=True, cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = shortest_augmenting_path(G, "s", "t", two_phase=False, cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = edmonds_karp(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = dinitz(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + R = boykov_kolmogorov(G, "s", "t", cutoff=k) + assert k <= R.graph["flow_value"] <= (2 * k) + + def test_complete_graph_cutoff(self): + G = nx.complete_graph(5) + nx.set_edge_attributes(G, {(u, v): 1 for u, v in G.edges()}, "capacity") + for flow_func in [ + shortest_augmenting_path, + edmonds_karp, + dinitz, + boykov_kolmogorov, + ]: + for cutoff in [3, 2, 1]: + result = nx.maximum_flow_value( + G, 0, 4, flow_func=flow_func, cutoff=cutoff + ) + assert cutoff == result, f"cutoff error in {flow_func.__name__}" diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow_large_graph.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow_large_graph.py new file mode 100644 index 00000000..b395cbc8 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_maxflow_large_graph.py @@ -0,0 +1,156 @@ +"""Maximum flow algorithms test suite on large graphs.""" + +import bz2 +import importlib.resources +import os +import pickle + +import pytest + +import networkx as nx +from networkx.algorithms.flow import ( + boykov_kolmogorov, + build_flow_dict, + build_residual_network, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +) + +flow_funcs = [ + boykov_kolmogorov, + dinitz, + edmonds_karp, + preflow_push, + shortest_augmenting_path, +] + + +def gen_pyramid(N): + # This graph admits a flow of value 1 for which every arc is at + # capacity (except the arcs incident to the sink which have + # infinite capacity). + G = nx.DiGraph() + + for i in range(N - 1): + cap = 1.0 / (i + 2) + for j in range(i + 1): + G.add_edge((i, j), (i + 1, j), capacity=cap) + cap = 1.0 / (i + 1) - cap + G.add_edge((i, j), (i + 1, j + 1), capacity=cap) + cap = 1.0 / (i + 2) - cap + + for j in range(N): + G.add_edge((N - 1, j), "t") + + return G + + +def read_graph(name): + fname = ( + importlib.resources.files("networkx.algorithms.flow.tests") + / f"{name}.gpickle.bz2" + ) + + with bz2.BZ2File(fname, "rb") as f: + G = pickle.load(f) + return G + + +def validate_flows(G, s, t, soln_value, R, flow_func): + flow_value = R.graph["flow_value"] + flow_dict = build_flow_dict(G, R) + errmsg = f"Assertion failed in function: {flow_func.__name__}" + assert soln_value == flow_value, errmsg + assert set(G) == set(flow_dict), errmsg + for u in G: + assert set(G[u]) == set(flow_dict[u]), errmsg + excess = {u: 0 for u in flow_dict} + for u in flow_dict: + for v, flow in flow_dict[u].items(): + assert flow <= G[u][v].get("capacity", float("inf")), errmsg + assert flow >= 0, errmsg + excess[u] -= flow + excess[v] += flow + for u, exc in excess.items(): + if u == s: + assert exc == -soln_value, errmsg + elif u == t: + assert exc == soln_value, errmsg + else: + assert exc == 0, errmsg + + +class TestMaxflowLargeGraph: + def test_complete_graph(self): + N = 50 + G = nx.complete_graph(N) + nx.set_edge_attributes(G, 5, "capacity") + R = build_residual_network(G, "capacity") + kwargs = {"residual": R} + + for flow_func in flow_funcs: + kwargs["flow_func"] = flow_func + errmsg = f"Assertion failed in function: {flow_func.__name__}" + flow_value = nx.maximum_flow_value(G, 1, 2, **kwargs) + assert flow_value == 5 * (N - 1), errmsg + + def test_pyramid(self): + N = 10 + # N = 100 # this gives a graph with 5051 nodes + G = gen_pyramid(N) + R = build_residual_network(G, "capacity") + kwargs = {"residual": R} + + for flow_func in flow_funcs: + kwargs["flow_func"] = flow_func + errmsg = f"Assertion failed in function: {flow_func.__name__}" + flow_value = nx.maximum_flow_value(G, (0, 0), "t", **kwargs) + assert flow_value == pytest.approx(1.0, abs=1e-7) + + def test_gl1(self): + G = read_graph("gl1") + s = 1 + t = len(G) + R = build_residual_network(G, "capacity") + kwargs = {"residual": R} + + # do one flow_func to save time + flow_func = flow_funcs[0] + validate_flows(G, s, t, 156545, flow_func(G, s, t, **kwargs), flow_func) + + # for flow_func in flow_funcs: + # validate_flows(G, s, t, 156545, flow_func(G, s, t, **kwargs), + # flow_func) + + @pytest.mark.slow + def test_gw1(self): + G = read_graph("gw1") + s = 1 + t = len(G) + R = build_residual_network(G, "capacity") + kwargs = {"residual": R} + + for flow_func in flow_funcs: + validate_flows(G, s, t, 1202018, flow_func(G, s, t, **kwargs), flow_func) + + def test_wlm3(self): + G = read_graph("wlm3") + s = 1 + t = len(G) + R = build_residual_network(G, "capacity") + kwargs = {"residual": R} + + # do one flow_func to save time + flow_func = flow_funcs[0] + validate_flows(G, s, t, 11875108, flow_func(G, s, t, **kwargs), flow_func) + + # for flow_func in flow_funcs: + # validate_flows(G, s, t, 11875108, flow_func(G, s, t, **kwargs), + # flow_func) + + def test_preflow_push_global_relabel(self): + G = read_graph("gw1") + R = preflow_push(G, 1, len(G), global_relabel_freq=50) + assert R.graph["flow_value"] == 1202018 diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_mincost.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_mincost.py new file mode 100644 index 00000000..5b1794b1 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_mincost.py @@ -0,0 +1,476 @@ +import bz2 +import importlib.resources +import os +import pickle + +import pytest + +import networkx as nx + + +class TestMinCostFlow: + def test_simple_digraph(self): + G = nx.DiGraph() + G.add_node("a", demand=-5) + G.add_node("d", demand=5) + G.add_edge("a", "b", weight=3, capacity=4) + G.add_edge("a", "c", weight=6, capacity=10) + G.add_edge("b", "d", weight=1, capacity=9) + G.add_edge("c", "d", weight=2, capacity=5) + flowCost, H = nx.network_simplex(G) + soln = {"a": {"b": 4, "c": 1}, "b": {"d": 4}, "c": {"d": 1}, "d": {}} + assert flowCost == 24 + assert nx.min_cost_flow_cost(G) == 24 + assert H == soln + assert nx.min_cost_flow(G) == soln + assert nx.cost_of_flow(G, H) == 24 + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 24 + assert nx.cost_of_flow(G, H) == 24 + assert H == soln + + def test_negcycle_infcap(self): + G = nx.DiGraph() + G.add_node("s", demand=-5) + G.add_node("t", demand=5) + G.add_edge("s", "a", weight=1, capacity=3) + G.add_edge("a", "b", weight=3) + G.add_edge("c", "a", weight=-6) + G.add_edge("b", "d", weight=1) + G.add_edge("d", "c", weight=-2) + G.add_edge("d", "t", weight=1, capacity=3) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnbounded, nx.capacity_scaling, G) + + def test_sum_demands_not_zero(self): + G = nx.DiGraph() + G.add_node("s", demand=-5) + G.add_node("t", demand=4) + G.add_edge("s", "a", weight=1, capacity=3) + G.add_edge("a", "b", weight=3) + G.add_edge("a", "c", weight=-6) + G.add_edge("b", "d", weight=1) + G.add_edge("c", "d", weight=-2) + G.add_edge("d", "t", weight=1, capacity=3) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + + def test_no_flow_satisfying_demands(self): + G = nx.DiGraph() + G.add_node("s", demand=-5) + G.add_node("t", demand=5) + G.add_edge("s", "a", weight=1, capacity=3) + G.add_edge("a", "b", weight=3) + G.add_edge("a", "c", weight=-6) + G.add_edge("b", "d", weight=1) + G.add_edge("c", "d", weight=-2) + G.add_edge("d", "t", weight=1, capacity=3) + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + + def test_transshipment(self): + G = nx.DiGraph() + G.add_node("a", demand=1) + G.add_node("b", demand=-2) + G.add_node("c", demand=-2) + G.add_node("d", demand=3) + G.add_node("e", demand=-4) + G.add_node("f", demand=-4) + G.add_node("g", demand=3) + G.add_node("h", demand=2) + G.add_node("r", demand=3) + G.add_edge("a", "c", weight=3) + G.add_edge("r", "a", weight=2) + G.add_edge("b", "a", weight=9) + G.add_edge("r", "c", weight=0) + G.add_edge("b", "r", weight=-6) + G.add_edge("c", "d", weight=5) + G.add_edge("e", "r", weight=4) + G.add_edge("e", "f", weight=3) + G.add_edge("h", "b", weight=4) + G.add_edge("f", "d", weight=7) + G.add_edge("f", "h", weight=12) + G.add_edge("g", "d", weight=12) + G.add_edge("f", "g", weight=-1) + G.add_edge("h", "g", weight=-10) + flowCost, H = nx.network_simplex(G) + soln = { + "a": {"c": 0}, + "b": {"a": 0, "r": 2}, + "c": {"d": 3}, + "d": {}, + "e": {"r": 3, "f": 1}, + "f": {"d": 0, "g": 3, "h": 2}, + "g": {"d": 0}, + "h": {"b": 0, "g": 0}, + "r": {"a": 1, "c": 1}, + } + assert flowCost == 41 + assert nx.min_cost_flow_cost(G) == 41 + assert H == soln + assert nx.min_cost_flow(G) == soln + assert nx.cost_of_flow(G, H) == 41 + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 41 + assert nx.cost_of_flow(G, H) == 41 + assert H == soln + + def test_max_flow_min_cost(self): + G = nx.DiGraph() + G.add_edge("s", "a", bandwidth=6) + G.add_edge("s", "c", bandwidth=10, cost=10) + G.add_edge("a", "b", cost=6) + G.add_edge("b", "d", bandwidth=8, cost=7) + G.add_edge("c", "d", cost=10) + G.add_edge("d", "t", bandwidth=5, cost=5) + soln = { + "s": {"a": 5, "c": 0}, + "a": {"b": 5}, + "b": {"d": 5}, + "c": {"d": 0}, + "d": {"t": 5}, + "t": {}, + } + flow = nx.max_flow_min_cost(G, "s", "t", capacity="bandwidth", weight="cost") + assert flow == soln + assert nx.cost_of_flow(G, flow, weight="cost") == 90 + + G.add_edge("t", "s", cost=-100) + flowCost, flow = nx.capacity_scaling(G, capacity="bandwidth", weight="cost") + G.remove_edge("t", "s") + assert flowCost == -410 + assert flow["t"]["s"] == 5 + del flow["t"]["s"] + assert flow == soln + assert nx.cost_of_flow(G, flow, weight="cost") == 90 + + def test_digraph1(self): + # From Bradley, S. P., Hax, A. C. and Magnanti, T. L. Applied + # Mathematical Programming. Addison-Wesley, 1977. + G = nx.DiGraph() + G.add_node(1, demand=-20) + G.add_node(4, demand=5) + G.add_node(5, demand=15) + G.add_edges_from( + [ + (1, 2, {"capacity": 15, "weight": 4}), + (1, 3, {"capacity": 8, "weight": 4}), + (2, 3, {"weight": 2}), + (2, 4, {"capacity": 4, "weight": 2}), + (2, 5, {"capacity": 10, "weight": 6}), + (3, 4, {"capacity": 15, "weight": 1}), + (3, 5, {"capacity": 5, "weight": 3}), + (4, 5, {"weight": 2}), + (5, 3, {"capacity": 4, "weight": 1}), + ] + ) + flowCost, H = nx.network_simplex(G) + soln = { + 1: {2: 12, 3: 8}, + 2: {3: 8, 4: 4, 5: 0}, + 3: {4: 11, 5: 5}, + 4: {5: 10}, + 5: {3: 0}, + } + assert flowCost == 150 + assert nx.min_cost_flow_cost(G) == 150 + assert H == soln + assert nx.min_cost_flow(G) == soln + assert nx.cost_of_flow(G, H) == 150 + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 150 + assert H == soln + assert nx.cost_of_flow(G, H) == 150 + + def test_digraph2(self): + # Example from ticket #430 from mfrasca. Original source: + # http://www.cs.princeton.edu/courses/archive/spr03/cs226/lectures/mincost.4up.pdf, slide 11. + G = nx.DiGraph() + G.add_edge("s", 1, capacity=12) + G.add_edge("s", 2, capacity=6) + G.add_edge("s", 3, capacity=14) + G.add_edge(1, 2, capacity=11, weight=4) + G.add_edge(2, 3, capacity=9, weight=6) + G.add_edge(1, 4, capacity=5, weight=5) + G.add_edge(1, 5, capacity=2, weight=12) + G.add_edge(2, 5, capacity=4, weight=4) + G.add_edge(2, 6, capacity=2, weight=6) + G.add_edge(3, 6, capacity=31, weight=3) + G.add_edge(4, 5, capacity=18, weight=4) + G.add_edge(5, 6, capacity=9, weight=5) + G.add_edge(4, "t", capacity=3) + G.add_edge(5, "t", capacity=7) + G.add_edge(6, "t", capacity=22) + flow = nx.max_flow_min_cost(G, "s", "t") + soln = { + 1: {2: 6, 4: 5, 5: 1}, + 2: {3: 6, 5: 4, 6: 2}, + 3: {6: 20}, + 4: {5: 2, "t": 3}, + 5: {6: 0, "t": 7}, + 6: {"t": 22}, + "s": {1: 12, 2: 6, 3: 14}, + "t": {}, + } + assert flow == soln + + G.add_edge("t", "s", weight=-100) + flowCost, flow = nx.capacity_scaling(G) + G.remove_edge("t", "s") + assert flow["t"]["s"] == 32 + assert flowCost == -3007 + del flow["t"]["s"] + assert flow == soln + assert nx.cost_of_flow(G, flow) == 193 + + def test_digraph3(self): + """Combinatorial Optimization: Algorithms and Complexity, + Papadimitriou Steiglitz at page 140 has an example, 7.1, but that + admits multiple solutions, so I alter it a bit. From ticket #430 + by mfrasca.""" + + G = nx.DiGraph() + G.add_edge("s", "a") + G["s"]["a"].update({0: 2, 1: 4}) + G.add_edge("s", "b") + G["s"]["b"].update({0: 2, 1: 1}) + G.add_edge("a", "b") + G["a"]["b"].update({0: 5, 1: 2}) + G.add_edge("a", "t") + G["a"]["t"].update({0: 1, 1: 5}) + G.add_edge("b", "a") + G["b"]["a"].update({0: 1, 1: 3}) + G.add_edge("b", "t") + G["b"]["t"].update({0: 3, 1: 2}) + + "PS.ex.7.1: testing main function" + sol = nx.max_flow_min_cost(G, "s", "t", capacity=0, weight=1) + flow = sum(v for v in sol["s"].values()) + assert 4 == flow + assert 23 == nx.cost_of_flow(G, sol, weight=1) + assert sol["s"] == {"a": 2, "b": 2} + assert sol["a"] == {"b": 1, "t": 1} + assert sol["b"] == {"a": 0, "t": 3} + assert sol["t"] == {} + + G.add_edge("t", "s") + G["t"]["s"].update({1: -100}) + flowCost, sol = nx.capacity_scaling(G, capacity=0, weight=1) + G.remove_edge("t", "s") + flow = sum(v for v in sol["s"].values()) + assert 4 == flow + assert sol["t"]["s"] == 4 + assert flowCost == -377 + del sol["t"]["s"] + assert sol["s"] == {"a": 2, "b": 2} + assert sol["a"] == {"b": 1, "t": 1} + assert sol["b"] == {"a": 0, "t": 3} + assert sol["t"] == {} + assert nx.cost_of_flow(G, sol, weight=1) == 23 + + def test_zero_capacity_edges(self): + """Address issue raised in ticket #617 by arv.""" + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2, {"capacity": 1, "weight": 1}), + (1, 5, {"capacity": 1, "weight": 1}), + (2, 3, {"capacity": 0, "weight": 1}), + (2, 5, {"capacity": 1, "weight": 1}), + (5, 3, {"capacity": 2, "weight": 1}), + (5, 4, {"capacity": 0, "weight": 1}), + (3, 4, {"capacity": 2, "weight": 1}), + ] + ) + G.nodes[1]["demand"] = -1 + G.nodes[2]["demand"] = -1 + G.nodes[4]["demand"] = 2 + + flowCost, H = nx.network_simplex(G) + soln = {1: {2: 0, 5: 1}, 2: {3: 0, 5: 1}, 3: {4: 2}, 4: {}, 5: {3: 2, 4: 0}} + assert flowCost == 6 + assert nx.min_cost_flow_cost(G) == 6 + assert H == soln + assert nx.min_cost_flow(G) == soln + assert nx.cost_of_flow(G, H) == 6 + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 6 + assert H == soln + assert nx.cost_of_flow(G, H) == 6 + + def test_digon(self): + """Check if digons are handled properly. Taken from ticket + #618 by arv.""" + nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})] + edges = [ + (1, 2, {"capacity": 3, "weight": 600000}), + (2, 1, {"capacity": 2, "weight": 0}), + (2, 3, {"capacity": 5, "weight": 714285}), + (3, 2, {"capacity": 2, "weight": 0}), + ] + G = nx.DiGraph(edges) + G.add_nodes_from(nodes) + flowCost, H = nx.network_simplex(G) + soln = {1: {2: 0}, 2: {1: 0, 3: 4}, 3: {2: 0}} + assert flowCost == 2857140 + assert nx.min_cost_flow_cost(G) == 2857140 + assert H == soln + assert nx.min_cost_flow(G) == soln + assert nx.cost_of_flow(G, H) == 2857140 + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 2857140 + assert H == soln + assert nx.cost_of_flow(G, H) == 2857140 + + def test_deadend(self): + """Check if one-node cycles are handled properly. Taken from ticket + #2906 from @sshraven.""" + G = nx.DiGraph() + + G.add_nodes_from(range(5), demand=0) + G.nodes[4]["demand"] = -13 + G.nodes[3]["demand"] = 13 + + G.add_edges_from([(0, 2), (0, 3), (2, 1)], capacity=20, weight=0.1) + pytest.raises(nx.NetworkXUnfeasible, nx.min_cost_flow, G) + + def test_infinite_capacity_neg_digon(self): + """An infinite capacity negative cost digon results in an unbounded + instance.""" + nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})] + edges = [ + (1, 2, {"weight": -600}), + (2, 1, {"weight": 0}), + (2, 3, {"capacity": 5, "weight": 714285}), + (3, 2, {"capacity": 2, "weight": 0}), + ] + G = nx.DiGraph(edges) + G.add_nodes_from(nodes) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnbounded, nx.capacity_scaling, G) + + def test_finite_capacity_neg_digon(self): + """The digon should receive the maximum amount of flow it can handle. + Taken from ticket #749 by @chuongdo.""" + G = nx.DiGraph() + G.add_edge("a", "b", capacity=1, weight=-1) + G.add_edge("b", "a", capacity=1, weight=-1) + min_cost = -2 + assert nx.min_cost_flow_cost(G) == min_cost + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == -2 + assert H == {"a": {"b": 1}, "b": {"a": 1}} + assert nx.cost_of_flow(G, H) == -2 + + def test_multidigraph(self): + """Multidigraphs are acceptable.""" + G = nx.MultiDiGraph() + G.add_weighted_edges_from([(1, 2, 1), (2, 3, 2)], weight="capacity") + flowCost, H = nx.network_simplex(G) + assert flowCost == 0 + assert H == {1: {2: {0: 0}}, 2: {3: {0: 0}}, 3: {}} + + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 0 + assert H == {1: {2: {0: 0}}, 2: {3: {0: 0}}, 3: {}} + + def test_negative_selfloops(self): + """Negative selfloops should cause an exception if uncapacitated and + always be saturated otherwise. + """ + G = nx.DiGraph() + G.add_edge(1, 1, weight=-1) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnbounded, nx.capacity_scaling, G) + G[1][1]["capacity"] = 2 + flowCost, H = nx.network_simplex(G) + assert flowCost == -2 + assert H == {1: {1: 2}} + flowCost, H = nx.capacity_scaling(G) + assert flowCost == -2 + assert H == {1: {1: 2}} + + G = nx.MultiDiGraph() + G.add_edge(1, 1, "x", weight=-1) + G.add_edge(1, 1, "y", weight=1) + pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnbounded, nx.capacity_scaling, G) + G[1][1]["x"]["capacity"] = 2 + flowCost, H = nx.network_simplex(G) + assert flowCost == -2 + assert H == {1: {1: {"x": 2, "y": 0}}} + flowCost, H = nx.capacity_scaling(G) + assert flowCost == -2 + assert H == {1: {1: {"x": 2, "y": 0}}} + + def test_bone_shaped(self): + # From #1283 + G = nx.DiGraph() + G.add_node(0, demand=-4) + G.add_node(1, demand=2) + G.add_node(2, demand=2) + G.add_node(3, demand=4) + G.add_node(4, demand=-2) + G.add_node(5, demand=-2) + G.add_edge(0, 1, capacity=4) + G.add_edge(0, 2, capacity=4) + G.add_edge(4, 3, capacity=4) + G.add_edge(5, 3, capacity=4) + G.add_edge(0, 3, capacity=0) + flowCost, H = nx.network_simplex(G) + assert flowCost == 0 + assert H == {0: {1: 2, 2: 2, 3: 0}, 1: {}, 2: {}, 3: {}, 4: {3: 2}, 5: {3: 2}} + flowCost, H = nx.capacity_scaling(G) + assert flowCost == 0 + assert H == {0: {1: 2, 2: 2, 3: 0}, 1: {}, 2: {}, 3: {}, 4: {3: 2}, 5: {3: 2}} + + def test_exceptions(self): + G = nx.Graph() + pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G) + pytest.raises(nx.NetworkXNotImplemented, nx.capacity_scaling, G) + G = nx.MultiGraph() + pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G) + pytest.raises(nx.NetworkXNotImplemented, nx.capacity_scaling, G) + G = nx.DiGraph() + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + # pytest.raises(nx.NetworkXError, nx.capacity_scaling, G) + G.add_node(0, demand=float("inf")) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + G.nodes[0]["demand"] = 0 + G.add_node(1, demand=0) + G.add_edge(0, 1, weight=-float("inf")) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + G[0][1]["weight"] = 0 + G.add_edge(0, 0, weight=float("inf")) + pytest.raises(nx.NetworkXError, nx.network_simplex, G) + # pytest.raises(nx.NetworkXError, nx.capacity_scaling, G) + G[0][0]["weight"] = 0 + G[0][1]["capacity"] = -1 + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + # pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + G[0][1]["capacity"] = 0 + G[0][0]["capacity"] = -1 + pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G) + # pytest.raises(nx.NetworkXUnfeasible, nx.capacity_scaling, G) + + def test_large(self): + fname = ( + importlib.resources.files("networkx.algorithms.flow.tests") + / "netgen-2.gpickle.bz2" + ) + with bz2.BZ2File(fname, "rb") as f: + G = pickle.load(f) + flowCost, flowDict = nx.network_simplex(G) + assert 6749969302 == flowCost + assert 6749969302 == nx.cost_of_flow(G, flowDict) + flowCost, flowDict = nx.capacity_scaling(G) + assert 6749969302 == flowCost + assert 6749969302 == nx.cost_of_flow(G, flowDict) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py new file mode 100644 index 00000000..5b3b5f6d --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/test_networksimplex.py @@ -0,0 +1,387 @@ +import bz2
+import importlib.resources
+import os
+import pickle
+
+import pytest
+
+import networkx as nx
+
+
+@pytest.fixture
+def simple_flow_graph():
+ G = nx.DiGraph()
+ G.add_node("a", demand=0)
+ G.add_node("b", demand=-5)
+ G.add_node("c", demand=50000000)
+ G.add_node("d", demand=-49999995)
+ G.add_edge("a", "b", weight=3, capacity=4)
+ G.add_edge("a", "c", weight=6, capacity=10)
+ G.add_edge("b", "d", weight=1, capacity=9)
+ G.add_edge("c", "d", weight=2, capacity=5)
+ return G
+
+
+@pytest.fixture
+def simple_no_flow_graph():
+ G = nx.DiGraph()
+ G.add_node("s", demand=-5)
+ G.add_node("t", demand=5)
+ G.add_edge("s", "a", weight=1, capacity=3)
+ G.add_edge("a", "b", weight=3)
+ G.add_edge("a", "c", weight=-6)
+ G.add_edge("b", "d", weight=1)
+ G.add_edge("c", "d", weight=-2)
+ G.add_edge("d", "t", weight=1, capacity=3)
+ return G
+
+
+def get_flowcost_from_flowdict(G, flowDict):
+ """Returns flow cost calculated from flow dictionary"""
+ flowCost = 0
+ for u in flowDict:
+ for v in flowDict[u]:
+ flowCost += flowDict[u][v] * G[u][v]["weight"]
+ return flowCost
+
+
+def test_infinite_demand_raise(simple_flow_graph):
+ G = simple_flow_graph
+ inf = float("inf")
+ nx.set_node_attributes(G, {"a": {"demand": inf}})
+ pytest.raises(nx.NetworkXError, nx.network_simplex, G)
+
+
+def test_neg_infinite_demand_raise(simple_flow_graph):
+ G = simple_flow_graph
+ inf = float("inf")
+ nx.set_node_attributes(G, {"a": {"demand": -inf}})
+ pytest.raises(nx.NetworkXError, nx.network_simplex, G)
+
+
+def test_infinite_weight_raise(simple_flow_graph):
+ G = simple_flow_graph
+ inf = float("inf")
+ nx.set_edge_attributes(
+ G, {("a", "b"): {"weight": inf}, ("b", "d"): {"weight": inf}}
+ )
+ pytest.raises(nx.NetworkXError, nx.network_simplex, G)
+
+
+def test_nonzero_net_demand_raise(simple_flow_graph):
+ G = simple_flow_graph
+ nx.set_node_attributes(G, {"b": {"demand": -4}})
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_negative_capacity_raise(simple_flow_graph):
+ G = simple_flow_graph
+ nx.set_edge_attributes(G, {("a", "b"): {"weight": 1}, ("b", "d"): {"capacity": -9}})
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_no_flow_satisfying_demands(simple_no_flow_graph):
+ G = simple_no_flow_graph
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_sum_demands_not_zero(simple_no_flow_graph):
+ G = simple_no_flow_graph
+ nx.set_node_attributes(G, {"t": {"demand": 4}})
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_google_or_tools_example():
+ """
+ https://developers.google.com/optimization/flow/mincostflow
+ """
+ G = nx.DiGraph()
+ start_nodes = [0, 0, 1, 1, 1, 2, 2, 3, 4]
+ end_nodes = [1, 2, 2, 3, 4, 3, 4, 4, 2]
+ capacities = [15, 8, 20, 4, 10, 15, 4, 20, 5]
+ unit_costs = [4, 4, 2, 2, 6, 1, 3, 2, 3]
+ supplies = [20, 0, 0, -5, -15]
+ answer = 150
+
+ for i in range(len(supplies)):
+ G.add_node(i, demand=(-1) * supplies[i]) # supplies are negative of demand
+
+ for i in range(len(start_nodes)):
+ G.add_edge(
+ start_nodes[i], end_nodes[i], weight=unit_costs[i], capacity=capacities[i]
+ )
+
+ flowCost, flowDict = nx.network_simplex(G)
+ assert flowCost == answer
+ assert flowCost == get_flowcost_from_flowdict(G, flowDict)
+
+
+def test_google_or_tools_example2():
+ """
+ https://developers.google.com/optimization/flow/mincostflow
+ """
+ G = nx.DiGraph()
+ start_nodes = [0, 0, 1, 1, 1, 2, 2, 3, 4, 3]
+ end_nodes = [1, 2, 2, 3, 4, 3, 4, 4, 2, 5]
+ capacities = [15, 8, 20, 4, 10, 15, 4, 20, 5, 10]
+ unit_costs = [4, 4, 2, 2, 6, 1, 3, 2, 3, 4]
+ supplies = [23, 0, 0, -5, -15, -3]
+ answer = 183
+
+ for i in range(len(supplies)):
+ G.add_node(i, demand=(-1) * supplies[i]) # supplies are negative of demand
+
+ for i in range(len(start_nodes)):
+ G.add_edge(
+ start_nodes[i], end_nodes[i], weight=unit_costs[i], capacity=capacities[i]
+ )
+
+ flowCost, flowDict = nx.network_simplex(G)
+ assert flowCost == answer
+ assert flowCost == get_flowcost_from_flowdict(G, flowDict)
+
+
+def test_large():
+ fname = (
+ importlib.resources.files("networkx.algorithms.flow.tests")
+ / "netgen-2.gpickle.bz2"
+ )
+
+ with bz2.BZ2File(fname, "rb") as f:
+ G = pickle.load(f)
+ flowCost, flowDict = nx.network_simplex(G)
+ assert 6749969302 == flowCost
+ assert 6749969302 == nx.cost_of_flow(G, flowDict)
+
+
+def test_simple_digraph():
+ G = nx.DiGraph()
+ G.add_node("a", demand=-5)
+ G.add_node("d", demand=5)
+ G.add_edge("a", "b", weight=3, capacity=4)
+ G.add_edge("a", "c", weight=6, capacity=10)
+ G.add_edge("b", "d", weight=1, capacity=9)
+ G.add_edge("c", "d", weight=2, capacity=5)
+ flowCost, H = nx.network_simplex(G)
+ soln = {"a": {"b": 4, "c": 1}, "b": {"d": 4}, "c": {"d": 1}, "d": {}}
+ assert flowCost == 24
+ assert nx.min_cost_flow_cost(G) == 24
+ assert H == soln
+
+
+def test_negcycle_infcap():
+ G = nx.DiGraph()
+ G.add_node("s", demand=-5)
+ G.add_node("t", demand=5)
+ G.add_edge("s", "a", weight=1, capacity=3)
+ G.add_edge("a", "b", weight=3)
+ G.add_edge("c", "a", weight=-6)
+ G.add_edge("b", "d", weight=1)
+ G.add_edge("d", "c", weight=-2)
+ G.add_edge("d", "t", weight=1, capacity=3)
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_transshipment():
+ G = nx.DiGraph()
+ G.add_node("a", demand=1)
+ G.add_node("b", demand=-2)
+ G.add_node("c", demand=-2)
+ G.add_node("d", demand=3)
+ G.add_node("e", demand=-4)
+ G.add_node("f", demand=-4)
+ G.add_node("g", demand=3)
+ G.add_node("h", demand=2)
+ G.add_node("r", demand=3)
+ G.add_edge("a", "c", weight=3)
+ G.add_edge("r", "a", weight=2)
+ G.add_edge("b", "a", weight=9)
+ G.add_edge("r", "c", weight=0)
+ G.add_edge("b", "r", weight=-6)
+ G.add_edge("c", "d", weight=5)
+ G.add_edge("e", "r", weight=4)
+ G.add_edge("e", "f", weight=3)
+ G.add_edge("h", "b", weight=4)
+ G.add_edge("f", "d", weight=7)
+ G.add_edge("f", "h", weight=12)
+ G.add_edge("g", "d", weight=12)
+ G.add_edge("f", "g", weight=-1)
+ G.add_edge("h", "g", weight=-10)
+ flowCost, H = nx.network_simplex(G)
+ soln = {
+ "a": {"c": 0},
+ "b": {"a": 0, "r": 2},
+ "c": {"d": 3},
+ "d": {},
+ "e": {"r": 3, "f": 1},
+ "f": {"d": 0, "g": 3, "h": 2},
+ "g": {"d": 0},
+ "h": {"b": 0, "g": 0},
+ "r": {"a": 1, "c": 1},
+ }
+ assert flowCost == 41
+ assert H == soln
+
+
+def test_digraph1():
+ # From Bradley, S. P., Hax, A. C. and Magnanti, T. L. Applied
+ # Mathematical Programming. Addison-Wesley, 1977.
+ G = nx.DiGraph()
+ G.add_node(1, demand=-20)
+ G.add_node(4, demand=5)
+ G.add_node(5, demand=15)
+ G.add_edges_from(
+ [
+ (1, 2, {"capacity": 15, "weight": 4}),
+ (1, 3, {"capacity": 8, "weight": 4}),
+ (2, 3, {"weight": 2}),
+ (2, 4, {"capacity": 4, "weight": 2}),
+ (2, 5, {"capacity": 10, "weight": 6}),
+ (3, 4, {"capacity": 15, "weight": 1}),
+ (3, 5, {"capacity": 5, "weight": 3}),
+ (4, 5, {"weight": 2}),
+ (5, 3, {"capacity": 4, "weight": 1}),
+ ]
+ )
+ flowCost, H = nx.network_simplex(G)
+ soln = {
+ 1: {2: 12, 3: 8},
+ 2: {3: 8, 4: 4, 5: 0},
+ 3: {4: 11, 5: 5},
+ 4: {5: 10},
+ 5: {3: 0},
+ }
+ assert flowCost == 150
+ assert nx.min_cost_flow_cost(G) == 150
+ assert H == soln
+
+
+def test_zero_capacity_edges():
+ """Address issue raised in ticket #617 by arv."""
+ G = nx.DiGraph()
+ G.add_edges_from(
+ [
+ (1, 2, {"capacity": 1, "weight": 1}),
+ (1, 5, {"capacity": 1, "weight": 1}),
+ (2, 3, {"capacity": 0, "weight": 1}),
+ (2, 5, {"capacity": 1, "weight": 1}),
+ (5, 3, {"capacity": 2, "weight": 1}),
+ (5, 4, {"capacity": 0, "weight": 1}),
+ (3, 4, {"capacity": 2, "weight": 1}),
+ ]
+ )
+ G.nodes[1]["demand"] = -1
+ G.nodes[2]["demand"] = -1
+ G.nodes[4]["demand"] = 2
+
+ flowCost, H = nx.network_simplex(G)
+ soln = {1: {2: 0, 5: 1}, 2: {3: 0, 5: 1}, 3: {4: 2}, 4: {}, 5: {3: 2, 4: 0}}
+ assert flowCost == 6
+ assert nx.min_cost_flow_cost(G) == 6
+ assert H == soln
+
+
+def test_digon():
+ """Check if digons are handled properly. Taken from ticket
+ #618 by arv."""
+ nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})]
+ edges = [
+ (1, 2, {"capacity": 3, "weight": 600000}),
+ (2, 1, {"capacity": 2, "weight": 0}),
+ (2, 3, {"capacity": 5, "weight": 714285}),
+ (3, 2, {"capacity": 2, "weight": 0}),
+ ]
+ G = nx.DiGraph(edges)
+ G.add_nodes_from(nodes)
+ flowCost, H = nx.network_simplex(G)
+ soln = {1: {2: 0}, 2: {1: 0, 3: 4}, 3: {2: 0}}
+ assert flowCost == 2857140
+
+
+def test_deadend():
+ """Check if one-node cycles are handled properly. Taken from ticket
+ #2906 from @sshraven."""
+ G = nx.DiGraph()
+
+ G.add_nodes_from(range(5), demand=0)
+ G.nodes[4]["demand"] = -13
+ G.nodes[3]["demand"] = 13
+
+ G.add_edges_from([(0, 2), (0, 3), (2, 1)], capacity=20, weight=0.1)
+ pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
+
+
+def test_infinite_capacity_neg_digon():
+ """An infinite capacity negative cost digon results in an unbounded
+ instance."""
+ nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})]
+ edges = [
+ (1, 2, {"weight": -600}),
+ (2, 1, {"weight": 0}),
+ (2, 3, {"capacity": 5, "weight": 714285}),
+ (3, 2, {"capacity": 2, "weight": 0}),
+ ]
+ G = nx.DiGraph(edges)
+ G.add_nodes_from(nodes)
+ pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G)
+
+
+def test_multidigraph():
+ """Multidigraphs are acceptable."""
+ G = nx.MultiDiGraph()
+ G.add_weighted_edges_from([(1, 2, 1), (2, 3, 2)], weight="capacity")
+ flowCost, H = nx.network_simplex(G)
+ assert flowCost == 0
+ assert H == {1: {2: {0: 0}}, 2: {3: {0: 0}}, 3: {}}
+
+
+def test_negative_selfloops():
+ """Negative selfloops should cause an exception if uncapacitated and
+ always be saturated otherwise.
+ """
+ G = nx.DiGraph()
+ G.add_edge(1, 1, weight=-1)
+ pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G)
+
+ G[1][1]["capacity"] = 2
+ flowCost, H = nx.network_simplex(G)
+ assert flowCost == -2
+ assert H == {1: {1: 2}}
+
+ G = nx.MultiDiGraph()
+ G.add_edge(1, 1, "x", weight=-1)
+ G.add_edge(1, 1, "y", weight=1)
+ pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G)
+
+ G[1][1]["x"]["capacity"] = 2
+ flowCost, H = nx.network_simplex(G)
+ assert flowCost == -2
+ assert H == {1: {1: {"x": 2, "y": 0}}}
+
+
+def test_bone_shaped():
+ # From #1283
+ G = nx.DiGraph()
+ G.add_node(0, demand=-4)
+ G.add_node(1, demand=2)
+ G.add_node(2, demand=2)
+ G.add_node(3, demand=4)
+ G.add_node(4, demand=-2)
+ G.add_node(5, demand=-2)
+ G.add_edge(0, 1, capacity=4)
+ G.add_edge(0, 2, capacity=4)
+ G.add_edge(4, 3, capacity=4)
+ G.add_edge(5, 3, capacity=4)
+ G.add_edge(0, 3, capacity=0)
+ flowCost, H = nx.network_simplex(G)
+ assert flowCost == 0
+ assert H == {0: {1: 2, 2: 2, 3: 0}, 1: {}, 2: {}, 3: {}, 4: {3: 2}, 5: {3: 2}}
+
+
+def test_graphs_type_exceptions():
+ G = nx.Graph()
+ pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G)
+ G = nx.MultiGraph()
+ pytest.raises(nx.NetworkXNotImplemented, nx.network_simplex, G)
+ G = nx.DiGraph()
+ pytest.raises(nx.NetworkXError, nx.network_simplex, G)
diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/wlm3.gpickle.bz2 b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/wlm3.gpickle.bz2 Binary files differnew file mode 100644 index 00000000..8ce935a8 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/flow/tests/wlm3.gpickle.bz2 |