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diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/similarity.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/similarity.py new file mode 100644 index 00000000..3c601a72 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/similarity.py @@ -0,0 +1,1780 @@ +"""Functions measuring similarity using graph edit distance. + +The graph edit distance is the number of edge/node changes needed +to make two graphs isomorphic. + +The default algorithm/implementation is sub-optimal for some graphs. +The problem of finding the exact Graph Edit Distance (GED) is NP-hard +so it is often slow. If the simple interface `graph_edit_distance` +takes too long for your graph, try `optimize_graph_edit_distance` +and/or `optimize_edit_paths`. + +At the same time, I encourage capable people to investigate +alternative GED algorithms, in order to improve the choices available. +""" + +import math +import time +import warnings +from dataclasses import dataclass +from itertools import product + +import networkx as nx +from networkx.utils import np_random_state + +__all__ = [ + "graph_edit_distance", + "optimal_edit_paths", + "optimize_graph_edit_distance", + "optimize_edit_paths", + "simrank_similarity", + "panther_similarity", + "generate_random_paths", +] + + +def debug_print(*args, **kwargs): + print(*args, **kwargs) + + +@nx._dispatchable( + graphs={"G1": 0, "G2": 1}, preserve_edge_attrs=True, preserve_node_attrs=True +) +def graph_edit_distance( + G1, + G2, + node_match=None, + edge_match=None, + node_subst_cost=None, + node_del_cost=None, + node_ins_cost=None, + edge_subst_cost=None, + edge_del_cost=None, + edge_ins_cost=None, + roots=None, + upper_bound=None, + timeout=None, +): + """Returns GED (graph edit distance) between graphs G1 and G2. + + Graph edit distance is a graph similarity measure analogous to + Levenshtein distance for strings. It is defined as minimum cost + of edit path (sequence of node and edge edit operations) + transforming graph G1 to graph isomorphic to G2. + + Parameters + ---------- + G1, G2: graphs + The two graphs G1 and G2 must be of the same type. + + node_match : callable + A function that returns True if node n1 in G1 and n2 in G2 + should be considered equal during matching. + + The function will be called like + + node_match(G1.nodes[n1], G2.nodes[n2]). + + That is, the function will receive the node attribute + dictionaries for n1 and n2 as inputs. + + Ignored if node_subst_cost is specified. If neither + node_match nor node_subst_cost are specified then node + attributes are not considered. + + edge_match : callable + A function that returns True if the edge attribute dictionaries + for the pair of nodes (u1, v1) in G1 and (u2, v2) in G2 should + be considered equal during matching. + + The function will be called like + + edge_match(G1[u1][v1], G2[u2][v2]). + + That is, the function will receive the edge attribute + dictionaries of the edges under consideration. + + Ignored if edge_subst_cost is specified. If neither + edge_match nor edge_subst_cost are specified then edge + attributes are not considered. + + node_subst_cost, node_del_cost, node_ins_cost : callable + Functions that return the costs of node substitution, node + deletion, and node insertion, respectively. + + The functions will be called like + + node_subst_cost(G1.nodes[n1], G2.nodes[n2]), + node_del_cost(G1.nodes[n1]), + node_ins_cost(G2.nodes[n2]). + + That is, the functions will receive the node attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function node_subst_cost overrides node_match if specified. + If neither node_match nor node_subst_cost are specified then + default node substitution cost of 0 is used (node attributes + are not considered during matching). + + If node_del_cost is not specified then default node deletion + cost of 1 is used. If node_ins_cost is not specified then + default node insertion cost of 1 is used. + + edge_subst_cost, edge_del_cost, edge_ins_cost : callable + Functions that return the costs of edge substitution, edge + deletion, and edge insertion, respectively. + + The functions will be called like + + edge_subst_cost(G1[u1][v1], G2[u2][v2]), + edge_del_cost(G1[u1][v1]), + edge_ins_cost(G2[u2][v2]). + + That is, the functions will receive the edge attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function edge_subst_cost overrides edge_match if specified. + If neither edge_match nor edge_subst_cost are specified then + default edge substitution cost of 0 is used (edge attributes + are not considered during matching). + + If edge_del_cost is not specified then default edge deletion + cost of 1 is used. If edge_ins_cost is not specified then + default edge insertion cost of 1 is used. + + roots : 2-tuple + Tuple where first element is a node in G1 and the second + is a node in G2. + These nodes are forced to be matched in the comparison to + allow comparison between rooted graphs. + + upper_bound : numeric + Maximum edit distance to consider. Return None if no edit + distance under or equal to upper_bound exists. + + timeout : numeric + Maximum number of seconds to execute. + After timeout is met, the current best GED is returned. + + Examples + -------- + >>> G1 = nx.cycle_graph(6) + >>> G2 = nx.wheel_graph(7) + >>> nx.graph_edit_distance(G1, G2) + 7.0 + + >>> G1 = nx.star_graph(5) + >>> G2 = nx.star_graph(5) + >>> nx.graph_edit_distance(G1, G2, roots=(0, 0)) + 0.0 + >>> nx.graph_edit_distance(G1, G2, roots=(1, 0)) + 8.0 + + See Also + -------- + optimal_edit_paths, optimize_graph_edit_distance, + + is_isomorphic: test for graph edit distance of 0 + + References + ---------- + .. [1] Zeina Abu-Aisheh, Romain Raveaux, Jean-Yves Ramel, Patrick + Martineau. An Exact Graph Edit Distance Algorithm for Solving + Pattern Recognition Problems. 4th International Conference on + Pattern Recognition Applications and Methods 2015, Jan 2015, + Lisbon, Portugal. 2015, + <10.5220/0005209202710278>. <hal-01168816> + https://hal.archives-ouvertes.fr/hal-01168816 + + """ + bestcost = None + for _, _, cost in optimize_edit_paths( + G1, + G2, + node_match, + edge_match, + node_subst_cost, + node_del_cost, + node_ins_cost, + edge_subst_cost, + edge_del_cost, + edge_ins_cost, + upper_bound, + True, + roots, + timeout, + ): + # assert bestcost is None or cost < bestcost + bestcost = cost + return bestcost + + +@nx._dispatchable(graphs={"G1": 0, "G2": 1}) +def optimal_edit_paths( + G1, + G2, + node_match=None, + edge_match=None, + node_subst_cost=None, + node_del_cost=None, + node_ins_cost=None, + edge_subst_cost=None, + edge_del_cost=None, + edge_ins_cost=None, + upper_bound=None, +): + """Returns all minimum-cost edit paths transforming G1 to G2. + + Graph edit path is a sequence of node and edge edit operations + transforming graph G1 to graph isomorphic to G2. Edit operations + include substitutions, deletions, and insertions. + + Parameters + ---------- + G1, G2: graphs + The two graphs G1 and G2 must be of the same type. + + node_match : callable + A function that returns True if node n1 in G1 and n2 in G2 + should be considered equal during matching. + + The function will be called like + + node_match(G1.nodes[n1], G2.nodes[n2]). + + That is, the function will receive the node attribute + dictionaries for n1 and n2 as inputs. + + Ignored if node_subst_cost is specified. If neither + node_match nor node_subst_cost are specified then node + attributes are not considered. + + edge_match : callable + A function that returns True if the edge attribute dictionaries + for the pair of nodes (u1, v1) in G1 and (u2, v2) in G2 should + be considered equal during matching. + + The function will be called like + + edge_match(G1[u1][v1], G2[u2][v2]). + + That is, the function will receive the edge attribute + dictionaries of the edges under consideration. + + Ignored if edge_subst_cost is specified. If neither + edge_match nor edge_subst_cost are specified then edge + attributes are not considered. + + node_subst_cost, node_del_cost, node_ins_cost : callable + Functions that return the costs of node substitution, node + deletion, and node insertion, respectively. + + The functions will be called like + + node_subst_cost(G1.nodes[n1], G2.nodes[n2]), + node_del_cost(G1.nodes[n1]), + node_ins_cost(G2.nodes[n2]). + + That is, the functions will receive the node attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function node_subst_cost overrides node_match if specified. + If neither node_match nor node_subst_cost are specified then + default node substitution cost of 0 is used (node attributes + are not considered during matching). + + If node_del_cost is not specified then default node deletion + cost of 1 is used. If node_ins_cost is not specified then + default node insertion cost of 1 is used. + + edge_subst_cost, edge_del_cost, edge_ins_cost : callable + Functions that return the costs of edge substitution, edge + deletion, and edge insertion, respectively. + + The functions will be called like + + edge_subst_cost(G1[u1][v1], G2[u2][v2]), + edge_del_cost(G1[u1][v1]), + edge_ins_cost(G2[u2][v2]). + + That is, the functions will receive the edge attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function edge_subst_cost overrides edge_match if specified. + If neither edge_match nor edge_subst_cost are specified then + default edge substitution cost of 0 is used (edge attributes + are not considered during matching). + + If edge_del_cost is not specified then default edge deletion + cost of 1 is used. If edge_ins_cost is not specified then + default edge insertion cost of 1 is used. + + upper_bound : numeric + Maximum edit distance to consider. + + Returns + ------- + edit_paths : list of tuples (node_edit_path, edge_edit_path) + - node_edit_path : list of tuples ``(u, v)`` indicating node transformations + between `G1` and `G2`. ``u`` is `None` for insertion, ``v`` is `None` + for deletion. + - edge_edit_path : list of tuples ``((u1, v1), (u2, v2))`` indicating edge + transformations between `G1` and `G2`. ``(None, (u2,v2))`` for insertion + and ``((u1,v1), None)`` for deletion. + + cost : numeric + Optimal edit path cost (graph edit distance). When the cost + is zero, it indicates that `G1` and `G2` are isomorphic. + + Examples + -------- + >>> G1 = nx.cycle_graph(4) + >>> G2 = nx.wheel_graph(5) + >>> paths, cost = nx.optimal_edit_paths(G1, G2) + >>> len(paths) + 40 + >>> cost + 5.0 + + Notes + ----- + To transform `G1` into a graph isomorphic to `G2`, apply the node + and edge edits in the returned ``edit_paths``. + In the case of isomorphic graphs, the cost is zero, and the paths + represent different isomorphic mappings (isomorphisms). That is, the + edits involve renaming nodes and edges to match the structure of `G2`. + + See Also + -------- + graph_edit_distance, optimize_edit_paths + + References + ---------- + .. [1] Zeina Abu-Aisheh, Romain Raveaux, Jean-Yves Ramel, Patrick + Martineau. An Exact Graph Edit Distance Algorithm for Solving + Pattern Recognition Problems. 4th International Conference on + Pattern Recognition Applications and Methods 2015, Jan 2015, + Lisbon, Portugal. 2015, + <10.5220/0005209202710278>. <hal-01168816> + https://hal.archives-ouvertes.fr/hal-01168816 + + """ + paths = [] + bestcost = None + for vertex_path, edge_path, cost in optimize_edit_paths( + G1, + G2, + node_match, + edge_match, + node_subst_cost, + node_del_cost, + node_ins_cost, + edge_subst_cost, + edge_del_cost, + edge_ins_cost, + upper_bound, + False, + ): + # assert bestcost is None or cost <= bestcost + if bestcost is not None and cost < bestcost: + paths = [] + paths.append((vertex_path, edge_path)) + bestcost = cost + return paths, bestcost + + +@nx._dispatchable(graphs={"G1": 0, "G2": 1}) +def optimize_graph_edit_distance( + G1, + G2, + node_match=None, + edge_match=None, + node_subst_cost=None, + node_del_cost=None, + node_ins_cost=None, + edge_subst_cost=None, + edge_del_cost=None, + edge_ins_cost=None, + upper_bound=None, +): + """Returns consecutive approximations of GED (graph edit distance) + between graphs G1 and G2. + + Graph edit distance is a graph similarity measure analogous to + Levenshtein distance for strings. It is defined as minimum cost + of edit path (sequence of node and edge edit operations) + transforming graph G1 to graph isomorphic to G2. + + Parameters + ---------- + G1, G2: graphs + The two graphs G1 and G2 must be of the same type. + + node_match : callable + A function that returns True if node n1 in G1 and n2 in G2 + should be considered equal during matching. + + The function will be called like + + node_match(G1.nodes[n1], G2.nodes[n2]). + + That is, the function will receive the node attribute + dictionaries for n1 and n2 as inputs. + + Ignored if node_subst_cost is specified. If neither + node_match nor node_subst_cost are specified then node + attributes are not considered. + + edge_match : callable + A function that returns True if the edge attribute dictionaries + for the pair of nodes (u1, v1) in G1 and (u2, v2) in G2 should + be considered equal during matching. + + The function will be called like + + edge_match(G1[u1][v1], G2[u2][v2]). + + That is, the function will receive the edge attribute + dictionaries of the edges under consideration. + + Ignored if edge_subst_cost is specified. If neither + edge_match nor edge_subst_cost are specified then edge + attributes are not considered. + + node_subst_cost, node_del_cost, node_ins_cost : callable + Functions that return the costs of node substitution, node + deletion, and node insertion, respectively. + + The functions will be called like + + node_subst_cost(G1.nodes[n1], G2.nodes[n2]), + node_del_cost(G1.nodes[n1]), + node_ins_cost(G2.nodes[n2]). + + That is, the functions will receive the node attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function node_subst_cost overrides node_match if specified. + If neither node_match nor node_subst_cost are specified then + default node substitution cost of 0 is used (node attributes + are not considered during matching). + + If node_del_cost is not specified then default node deletion + cost of 1 is used. If node_ins_cost is not specified then + default node insertion cost of 1 is used. + + edge_subst_cost, edge_del_cost, edge_ins_cost : callable + Functions that return the costs of edge substitution, edge + deletion, and edge insertion, respectively. + + The functions will be called like + + edge_subst_cost(G1[u1][v1], G2[u2][v2]), + edge_del_cost(G1[u1][v1]), + edge_ins_cost(G2[u2][v2]). + + That is, the functions will receive the edge attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function edge_subst_cost overrides edge_match if specified. + If neither edge_match nor edge_subst_cost are specified then + default edge substitution cost of 0 is used (edge attributes + are not considered during matching). + + If edge_del_cost is not specified then default edge deletion + cost of 1 is used. If edge_ins_cost is not specified then + default edge insertion cost of 1 is used. + + upper_bound : numeric + Maximum edit distance to consider. + + Returns + ------- + Generator of consecutive approximations of graph edit distance. + + Examples + -------- + >>> G1 = nx.cycle_graph(6) + >>> G2 = nx.wheel_graph(7) + >>> for v in nx.optimize_graph_edit_distance(G1, G2): + ... minv = v + >>> minv + 7.0 + + See Also + -------- + graph_edit_distance, optimize_edit_paths + + References + ---------- + .. [1] Zeina Abu-Aisheh, Romain Raveaux, Jean-Yves Ramel, Patrick + Martineau. An Exact Graph Edit Distance Algorithm for Solving + Pattern Recognition Problems. 4th International Conference on + Pattern Recognition Applications and Methods 2015, Jan 2015, + Lisbon, Portugal. 2015, + <10.5220/0005209202710278>. <hal-01168816> + https://hal.archives-ouvertes.fr/hal-01168816 + """ + for _, _, cost in optimize_edit_paths( + G1, + G2, + node_match, + edge_match, + node_subst_cost, + node_del_cost, + node_ins_cost, + edge_subst_cost, + edge_del_cost, + edge_ins_cost, + upper_bound, + True, + ): + yield cost + + +@nx._dispatchable( + graphs={"G1": 0, "G2": 1}, preserve_edge_attrs=True, preserve_node_attrs=True +) +def optimize_edit_paths( + G1, + G2, + node_match=None, + edge_match=None, + node_subst_cost=None, + node_del_cost=None, + node_ins_cost=None, + edge_subst_cost=None, + edge_del_cost=None, + edge_ins_cost=None, + upper_bound=None, + strictly_decreasing=True, + roots=None, + timeout=None, +): + """GED (graph edit distance) calculation: advanced interface. + + Graph edit path is a sequence of node and edge edit operations + transforming graph G1 to graph isomorphic to G2. Edit operations + include substitutions, deletions, and insertions. + + Graph edit distance is defined as minimum cost of edit path. + + Parameters + ---------- + G1, G2: graphs + The two graphs G1 and G2 must be of the same type. + + node_match : callable + A function that returns True if node n1 in G1 and n2 in G2 + should be considered equal during matching. + + The function will be called like + + node_match(G1.nodes[n1], G2.nodes[n2]). + + That is, the function will receive the node attribute + dictionaries for n1 and n2 as inputs. + + Ignored if node_subst_cost is specified. If neither + node_match nor node_subst_cost are specified then node + attributes are not considered. + + edge_match : callable + A function that returns True if the edge attribute dictionaries + for the pair of nodes (u1, v1) in G1 and (u2, v2) in G2 should + be considered equal during matching. + + The function will be called like + + edge_match(G1[u1][v1], G2[u2][v2]). + + That is, the function will receive the edge attribute + dictionaries of the edges under consideration. + + Ignored if edge_subst_cost is specified. If neither + edge_match nor edge_subst_cost are specified then edge + attributes are not considered. + + node_subst_cost, node_del_cost, node_ins_cost : callable + Functions that return the costs of node substitution, node + deletion, and node insertion, respectively. + + The functions will be called like + + node_subst_cost(G1.nodes[n1], G2.nodes[n2]), + node_del_cost(G1.nodes[n1]), + node_ins_cost(G2.nodes[n2]). + + That is, the functions will receive the node attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function node_subst_cost overrides node_match if specified. + If neither node_match nor node_subst_cost are specified then + default node substitution cost of 0 is used (node attributes + are not considered during matching). + + If node_del_cost is not specified then default node deletion + cost of 1 is used. If node_ins_cost is not specified then + default node insertion cost of 1 is used. + + edge_subst_cost, edge_del_cost, edge_ins_cost : callable + Functions that return the costs of edge substitution, edge + deletion, and edge insertion, respectively. + + The functions will be called like + + edge_subst_cost(G1[u1][v1], G2[u2][v2]), + edge_del_cost(G1[u1][v1]), + edge_ins_cost(G2[u2][v2]). + + That is, the functions will receive the edge attribute + dictionaries as inputs. The functions are expected to return + positive numeric values. + + Function edge_subst_cost overrides edge_match if specified. + If neither edge_match nor edge_subst_cost are specified then + default edge substitution cost of 0 is used (edge attributes + are not considered during matching). + + If edge_del_cost is not specified then default edge deletion + cost of 1 is used. If edge_ins_cost is not specified then + default edge insertion cost of 1 is used. + + upper_bound : numeric + Maximum edit distance to consider. + + strictly_decreasing : bool + If True, return consecutive approximations of strictly + decreasing cost. Otherwise, return all edit paths of cost + less than or equal to the previous minimum cost. + + roots : 2-tuple + Tuple where first element is a node in G1 and the second + is a node in G2. + These nodes are forced to be matched in the comparison to + allow comparison between rooted graphs. + + timeout : numeric + Maximum number of seconds to execute. + After timeout is met, the current best GED is returned. + + Returns + ------- + Generator of tuples (node_edit_path, edge_edit_path, cost) + node_edit_path : list of tuples (u, v) + edge_edit_path : list of tuples ((u1, v1), (u2, v2)) + cost : numeric + + See Also + -------- + graph_edit_distance, optimize_graph_edit_distance, optimal_edit_paths + + References + ---------- + .. [1] Zeina Abu-Aisheh, Romain Raveaux, Jean-Yves Ramel, Patrick + Martineau. An Exact Graph Edit Distance Algorithm for Solving + Pattern Recognition Problems. 4th International Conference on + Pattern Recognition Applications and Methods 2015, Jan 2015, + Lisbon, Portugal. 2015, + <10.5220/0005209202710278>. <hal-01168816> + https://hal.archives-ouvertes.fr/hal-01168816 + + """ + # TODO: support DiGraph + + import numpy as np + import scipy as sp + + @dataclass + class CostMatrix: + C: ... + lsa_row_ind: ... + lsa_col_ind: ... + ls: ... + + def make_CostMatrix(C, m, n): + # assert(C.shape == (m + n, m + n)) + lsa_row_ind, lsa_col_ind = sp.optimize.linear_sum_assignment(C) + + # Fixup dummy assignments: + # each substitution i<->j should have dummy assignment m+j<->n+i + # NOTE: fast reduce of Cv relies on it + # Create masks for substitution and dummy indices + is_subst = (lsa_row_ind < m) & (lsa_col_ind < n) + is_dummy = (lsa_row_ind >= m) & (lsa_col_ind >= n) + + # Map dummy assignments to the correct indices + lsa_row_ind[is_dummy] = lsa_col_ind[is_subst] + m + lsa_col_ind[is_dummy] = lsa_row_ind[is_subst] + n + + return CostMatrix( + C, lsa_row_ind, lsa_col_ind, C[lsa_row_ind, lsa_col_ind].sum() + ) + + def extract_C(C, i, j, m, n): + # assert(C.shape == (m + n, m + n)) + row_ind = [k in i or k - m in j for k in range(m + n)] + col_ind = [k in j or k - n in i for k in range(m + n)] + return C[row_ind, :][:, col_ind] + + def reduce_C(C, i, j, m, n): + # assert(C.shape == (m + n, m + n)) + row_ind = [k not in i and k - m not in j for k in range(m + n)] + col_ind = [k not in j and k - n not in i for k in range(m + n)] + return C[row_ind, :][:, col_ind] + + def reduce_ind(ind, i): + # assert set(ind) == set(range(len(ind))) + rind = ind[[k not in i for k in ind]] + for k in set(i): + rind[rind >= k] -= 1 + return rind + + def match_edges(u, v, pending_g, pending_h, Ce, matched_uv=None): + """ + Parameters: + u, v: matched vertices, u=None or v=None for + deletion/insertion + pending_g, pending_h: lists of edges not yet mapped + Ce: CostMatrix of pending edge mappings + matched_uv: partial vertex edit path + list of tuples (u, v) of previously matched vertex + mappings u<->v, u=None or v=None for + deletion/insertion + + Returns: + list of (i, j): indices of edge mappings g<->h + localCe: local CostMatrix of edge mappings + (basically submatrix of Ce at cross of rows i, cols j) + """ + M = len(pending_g) + N = len(pending_h) + # assert Ce.C.shape == (M + N, M + N) + + # only attempt to match edges after one node match has been made + # this will stop self-edges on the first node being automatically deleted + # even when a substitution is the better option + if matched_uv is None or len(matched_uv) == 0: + g_ind = [] + h_ind = [] + else: + g_ind = [ + i + for i in range(M) + if pending_g[i][:2] == (u, u) + or any( + pending_g[i][:2] in ((p, u), (u, p), (p, p)) for p, q in matched_uv + ) + ] + h_ind = [ + j + for j in range(N) + if pending_h[j][:2] == (v, v) + or any( + pending_h[j][:2] in ((q, v), (v, q), (q, q)) for p, q in matched_uv + ) + ] + + m = len(g_ind) + n = len(h_ind) + + if m or n: + C = extract_C(Ce.C, g_ind, h_ind, M, N) + # assert C.shape == (m + n, m + n) + + # Forbid structurally invalid matches + # NOTE: inf remembered from Ce construction + for k, i in enumerate(g_ind): + g = pending_g[i][:2] + for l, j in enumerate(h_ind): + h = pending_h[j][:2] + if nx.is_directed(G1) or nx.is_directed(G2): + if any( + g == (p, u) and h == (q, v) or g == (u, p) and h == (v, q) + for p, q in matched_uv + ): + continue + else: + if any( + g in ((p, u), (u, p)) and h in ((q, v), (v, q)) + for p, q in matched_uv + ): + continue + if g == (u, u) or any(g == (p, p) for p, q in matched_uv): + continue + if h == (v, v) or any(h == (q, q) for p, q in matched_uv): + continue + C[k, l] = inf + + localCe = make_CostMatrix(C, m, n) + ij = [ + ( + g_ind[k] if k < m else M + h_ind[l], + h_ind[l] if l < n else N + g_ind[k], + ) + for k, l in zip(localCe.lsa_row_ind, localCe.lsa_col_ind) + if k < m or l < n + ] + + else: + ij = [] + localCe = CostMatrix(np.empty((0, 0)), [], [], 0) + + return ij, localCe + + def reduce_Ce(Ce, ij, m, n): + if len(ij): + i, j = zip(*ij) + m_i = m - sum(1 for t in i if t < m) + n_j = n - sum(1 for t in j if t < n) + return make_CostMatrix(reduce_C(Ce.C, i, j, m, n), m_i, n_j) + return Ce + + def get_edit_ops( + matched_uv, pending_u, pending_v, Cv, pending_g, pending_h, Ce, matched_cost + ): + """ + Parameters: + matched_uv: partial vertex edit path + list of tuples (u, v) of vertex mappings u<->v, + u=None or v=None for deletion/insertion + pending_u, pending_v: lists of vertices not yet mapped + Cv: CostMatrix of pending vertex mappings + pending_g, pending_h: lists of edges not yet mapped + Ce: CostMatrix of pending edge mappings + matched_cost: cost of partial edit path + + Returns: + sequence of + (i, j): indices of vertex mapping u<->v + Cv_ij: reduced CostMatrix of pending vertex mappings + (basically Cv with row i, col j removed) + list of (x, y): indices of edge mappings g<->h + Ce_xy: reduced CostMatrix of pending edge mappings + (basically Ce with rows x, cols y removed) + cost: total cost of edit operation + NOTE: most promising ops first + """ + m = len(pending_u) + n = len(pending_v) + # assert Cv.C.shape == (m + n, m + n) + + # 1) a vertex mapping from optimal linear sum assignment + i, j = min( + (k, l) for k, l in zip(Cv.lsa_row_ind, Cv.lsa_col_ind) if k < m or l < n + ) + xy, localCe = match_edges( + pending_u[i] if i < m else None, + pending_v[j] if j < n else None, + pending_g, + pending_h, + Ce, + matched_uv, + ) + Ce_xy = reduce_Ce(Ce, xy, len(pending_g), len(pending_h)) + # assert Ce.ls <= localCe.ls + Ce_xy.ls + if prune(matched_cost + Cv.ls + localCe.ls + Ce_xy.ls): + pass + else: + # get reduced Cv efficiently + Cv_ij = CostMatrix( + reduce_C(Cv.C, (i,), (j,), m, n), + reduce_ind(Cv.lsa_row_ind, (i, m + j)), + reduce_ind(Cv.lsa_col_ind, (j, n + i)), + Cv.ls - Cv.C[i, j], + ) + yield (i, j), Cv_ij, xy, Ce_xy, Cv.C[i, j] + localCe.ls + + # 2) other candidates, sorted by lower-bound cost estimate + other = [] + fixed_i, fixed_j = i, j + if m <= n: + candidates = ( + (t, fixed_j) + for t in range(m + n) + if t != fixed_i and (t < m or t == m + fixed_j) + ) + else: + candidates = ( + (fixed_i, t) + for t in range(m + n) + if t != fixed_j and (t < n or t == n + fixed_i) + ) + for i, j in candidates: + if prune(matched_cost + Cv.C[i, j] + Ce.ls): + continue + Cv_ij = make_CostMatrix( + reduce_C(Cv.C, (i,), (j,), m, n), + m - 1 if i < m else m, + n - 1 if j < n else n, + ) + # assert Cv.ls <= Cv.C[i, j] + Cv_ij.ls + if prune(matched_cost + Cv.C[i, j] + Cv_ij.ls + Ce.ls): + continue + xy, localCe = match_edges( + pending_u[i] if i < m else None, + pending_v[j] if j < n else None, + pending_g, + pending_h, + Ce, + matched_uv, + ) + if prune(matched_cost + Cv.C[i, j] + Cv_ij.ls + localCe.ls): + continue + Ce_xy = reduce_Ce(Ce, xy, len(pending_g), len(pending_h)) + # assert Ce.ls <= localCe.ls + Ce_xy.ls + if prune(matched_cost + Cv.C[i, j] + Cv_ij.ls + localCe.ls + Ce_xy.ls): + continue + other.append(((i, j), Cv_ij, xy, Ce_xy, Cv.C[i, j] + localCe.ls)) + + yield from sorted(other, key=lambda t: t[4] + t[1].ls + t[3].ls) + + def get_edit_paths( + matched_uv, + pending_u, + pending_v, + Cv, + matched_gh, + pending_g, + pending_h, + Ce, + matched_cost, + ): + """ + Parameters: + matched_uv: partial vertex edit path + list of tuples (u, v) of vertex mappings u<->v, + u=None or v=None for deletion/insertion + pending_u, pending_v: lists of vertices not yet mapped + Cv: CostMatrix of pending vertex mappings + matched_gh: partial edge edit path + list of tuples (g, h) of edge mappings g<->h, + g=None or h=None for deletion/insertion + pending_g, pending_h: lists of edges not yet mapped + Ce: CostMatrix of pending edge mappings + matched_cost: cost of partial edit path + + Returns: + sequence of (vertex_path, edge_path, cost) + vertex_path: complete vertex edit path + list of tuples (u, v) of vertex mappings u<->v, + u=None or v=None for deletion/insertion + edge_path: complete edge edit path + list of tuples (g, h) of edge mappings g<->h, + g=None or h=None for deletion/insertion + cost: total cost of edit path + NOTE: path costs are non-increasing + """ + # debug_print('matched-uv:', matched_uv) + # debug_print('matched-gh:', matched_gh) + # debug_print('matched-cost:', matched_cost) + # debug_print('pending-u:', pending_u) + # debug_print('pending-v:', pending_v) + # debug_print(Cv.C) + # assert list(sorted(G1.nodes)) == list(sorted(list(u for u, v in matched_uv if u is not None) + pending_u)) + # assert list(sorted(G2.nodes)) == list(sorted(list(v for u, v in matched_uv if v is not None) + pending_v)) + # debug_print('pending-g:', pending_g) + # debug_print('pending-h:', pending_h) + # debug_print(Ce.C) + # assert list(sorted(G1.edges)) == list(sorted(list(g for g, h in matched_gh if g is not None) + pending_g)) + # assert list(sorted(G2.edges)) == list(sorted(list(h for g, h in matched_gh if h is not None) + pending_h)) + # debug_print() + + if prune(matched_cost + Cv.ls + Ce.ls): + return + + if not max(len(pending_u), len(pending_v)): + # assert not len(pending_g) + # assert not len(pending_h) + # path completed! + # assert matched_cost <= maxcost_value + nonlocal maxcost_value + maxcost_value = min(maxcost_value, matched_cost) + yield matched_uv, matched_gh, matched_cost + + else: + edit_ops = get_edit_ops( + matched_uv, + pending_u, + pending_v, + Cv, + pending_g, + pending_h, + Ce, + matched_cost, + ) + for ij, Cv_ij, xy, Ce_xy, edit_cost in edit_ops: + i, j = ij + # assert Cv.C[i, j] + sum(Ce.C[t] for t in xy) == edit_cost + if prune(matched_cost + edit_cost + Cv_ij.ls + Ce_xy.ls): + continue + + # dive deeper + u = pending_u.pop(i) if i < len(pending_u) else None + v = pending_v.pop(j) if j < len(pending_v) else None + matched_uv.append((u, v)) + for x, y in xy: + len_g = len(pending_g) + len_h = len(pending_h) + matched_gh.append( + ( + pending_g[x] if x < len_g else None, + pending_h[y] if y < len_h else None, + ) + ) + sortedx = sorted(x for x, y in xy) + sortedy = sorted(y for x, y in xy) + G = [ + (pending_g.pop(x) if x < len(pending_g) else None) + for x in reversed(sortedx) + ] + H = [ + (pending_h.pop(y) if y < len(pending_h) else None) + for y in reversed(sortedy) + ] + + yield from get_edit_paths( + matched_uv, + pending_u, + pending_v, + Cv_ij, + matched_gh, + pending_g, + pending_h, + Ce_xy, + matched_cost + edit_cost, + ) + + # backtrack + if u is not None: + pending_u.insert(i, u) + if v is not None: + pending_v.insert(j, v) + matched_uv.pop() + for x, g in zip(sortedx, reversed(G)): + if g is not None: + pending_g.insert(x, g) + for y, h in zip(sortedy, reversed(H)): + if h is not None: + pending_h.insert(y, h) + for _ in xy: + matched_gh.pop() + + # Initialization + + pending_u = list(G1.nodes) + pending_v = list(G2.nodes) + + initial_cost = 0 + if roots: + root_u, root_v = roots + if root_u not in pending_u or root_v not in pending_v: + raise nx.NodeNotFound("Root node not in graph.") + + # remove roots from pending + pending_u.remove(root_u) + pending_v.remove(root_v) + + # cost matrix of vertex mappings + m = len(pending_u) + n = len(pending_v) + C = np.zeros((m + n, m + n)) + if node_subst_cost: + C[0:m, 0:n] = np.array( + [ + node_subst_cost(G1.nodes[u], G2.nodes[v]) + for u in pending_u + for v in pending_v + ] + ).reshape(m, n) + if roots: + initial_cost = node_subst_cost(G1.nodes[root_u], G2.nodes[root_v]) + elif node_match: + C[0:m, 0:n] = np.array( + [ + 1 - int(node_match(G1.nodes[u], G2.nodes[v])) + for u in pending_u + for v in pending_v + ] + ).reshape(m, n) + if roots: + initial_cost = 1 - node_match(G1.nodes[root_u], G2.nodes[root_v]) + else: + # all zeroes + pass + # assert not min(m, n) or C[0:m, 0:n].min() >= 0 + if node_del_cost: + del_costs = [node_del_cost(G1.nodes[u]) for u in pending_u] + else: + del_costs = [1] * len(pending_u) + # assert not m or min(del_costs) >= 0 + if node_ins_cost: + ins_costs = [node_ins_cost(G2.nodes[v]) for v in pending_v] + else: + ins_costs = [1] * len(pending_v) + # assert not n or min(ins_costs) >= 0 + inf = C[0:m, 0:n].sum() + sum(del_costs) + sum(ins_costs) + 1 + C[0:m, n : n + m] = np.array( + [del_costs[i] if i == j else inf for i in range(m) for j in range(m)] + ).reshape(m, m) + C[m : m + n, 0:n] = np.array( + [ins_costs[i] if i == j else inf for i in range(n) for j in range(n)] + ).reshape(n, n) + Cv = make_CostMatrix(C, m, n) + # debug_print(f"Cv: {m} x {n}") + # debug_print(Cv.C) + + pending_g = list(G1.edges) + pending_h = list(G2.edges) + + # cost matrix of edge mappings + m = len(pending_g) + n = len(pending_h) + C = np.zeros((m + n, m + n)) + if edge_subst_cost: + C[0:m, 0:n] = np.array( + [ + edge_subst_cost(G1.edges[g], G2.edges[h]) + for g in pending_g + for h in pending_h + ] + ).reshape(m, n) + elif edge_match: + C[0:m, 0:n] = np.array( + [ + 1 - int(edge_match(G1.edges[g], G2.edges[h])) + for g in pending_g + for h in pending_h + ] + ).reshape(m, n) + else: + # all zeroes + pass + # assert not min(m, n) or C[0:m, 0:n].min() >= 0 + if edge_del_cost: + del_costs = [edge_del_cost(G1.edges[g]) for g in pending_g] + else: + del_costs = [1] * len(pending_g) + # assert not m or min(del_costs) >= 0 + if edge_ins_cost: + ins_costs = [edge_ins_cost(G2.edges[h]) for h in pending_h] + else: + ins_costs = [1] * len(pending_h) + # assert not n or min(ins_costs) >= 0 + inf = C[0:m, 0:n].sum() + sum(del_costs) + sum(ins_costs) + 1 + C[0:m, n : n + m] = np.array( + [del_costs[i] if i == j else inf for i in range(m) for j in range(m)] + ).reshape(m, m) + C[m : m + n, 0:n] = np.array( + [ins_costs[i] if i == j else inf for i in range(n) for j in range(n)] + ).reshape(n, n) + Ce = make_CostMatrix(C, m, n) + # debug_print(f'Ce: {m} x {n}') + # debug_print(Ce.C) + # debug_print() + + maxcost_value = Cv.C.sum() + Ce.C.sum() + 1 + + if timeout is not None: + if timeout <= 0: + raise nx.NetworkXError("Timeout value must be greater than 0") + start = time.perf_counter() + + def prune(cost): + if timeout is not None: + if time.perf_counter() - start > timeout: + return True + if upper_bound is not None: + if cost > upper_bound: + return True + if cost > maxcost_value: + return True + if strictly_decreasing and cost >= maxcost_value: + return True + return False + + # Now go! + + done_uv = [] if roots is None else [roots] + + for vertex_path, edge_path, cost in get_edit_paths( + done_uv, pending_u, pending_v, Cv, [], pending_g, pending_h, Ce, initial_cost + ): + # assert sorted(G1.nodes) == sorted(u for u, v in vertex_path if u is not None) + # assert sorted(G2.nodes) == sorted(v for u, v in vertex_path if v is not None) + # assert sorted(G1.edges) == sorted(g for g, h in edge_path if g is not None) + # assert sorted(G2.edges) == sorted(h for g, h in edge_path if h is not None) + # print(vertex_path, edge_path, cost, file = sys.stderr) + # assert cost == maxcost_value + yield list(vertex_path), list(edge_path), float(cost) + + +@nx._dispatchable +def simrank_similarity( + G, + source=None, + target=None, + importance_factor=0.9, + max_iterations=1000, + tolerance=1e-4, +): + """Returns the SimRank similarity of nodes in the graph ``G``. + + SimRank is a similarity metric that says "two objects are considered + to be similar if they are referenced by similar objects." [1]_. + + The pseudo-code definition from the paper is:: + + def simrank(G, u, v): + in_neighbors_u = G.predecessors(u) + in_neighbors_v = G.predecessors(v) + scale = C / (len(in_neighbors_u) * len(in_neighbors_v)) + return scale * sum( + simrank(G, w, x) for w, x in product(in_neighbors_u, in_neighbors_v) + ) + + where ``G`` is the graph, ``u`` is the source, ``v`` is the target, + and ``C`` is a float decay or importance factor between 0 and 1. + + The SimRank algorithm for determining node similarity is defined in + [2]_. + + Parameters + ---------- + G : NetworkX graph + A NetworkX graph + + source : node + If this is specified, the returned dictionary maps each node + ``v`` in the graph to the similarity between ``source`` and + ``v``. + + target : node + If both ``source`` and ``target`` are specified, the similarity + value between ``source`` and ``target`` is returned. If + ``target`` is specified but ``source`` is not, this argument is + ignored. + + importance_factor : float + The relative importance of indirect neighbors with respect to + direct neighbors. + + max_iterations : integer + Maximum number of iterations. + + tolerance : float + Error tolerance used to check convergence. When an iteration of + the algorithm finds that no similarity value changes more than + this amount, the algorithm halts. + + Returns + ------- + similarity : dictionary or float + If ``source`` and ``target`` are both ``None``, this returns a + dictionary of dictionaries, where keys are node pairs and value + are similarity of the pair of nodes. + + If ``source`` is not ``None`` but ``target`` is, this returns a + dictionary mapping node to the similarity of ``source`` and that + node. + + If neither ``source`` nor ``target`` is ``None``, this returns + the similarity value for the given pair of nodes. + + Raises + ------ + ExceededMaxIterations + If the algorithm does not converge within ``max_iterations``. + + NodeNotFound + If either ``source`` or ``target`` is not in `G`. + + Examples + -------- + >>> G = nx.cycle_graph(2) + >>> nx.simrank_similarity(G) + {0: {0: 1.0, 1: 0.0}, 1: {0: 0.0, 1: 1.0}} + >>> nx.simrank_similarity(G, source=0) + {0: 1.0, 1: 0.0} + >>> nx.simrank_similarity(G, source=0, target=0) + 1.0 + + The result of this function can be converted to a numpy array + representing the SimRank matrix by using the node order of the + graph to determine which row and column represent each node. + Other ordering of nodes is also possible. + + >>> import numpy as np + >>> sim = nx.simrank_similarity(G) + >>> np.array([[sim[u][v] for v in G] for u in G]) + array([[1., 0.], + [0., 1.]]) + >>> sim_1d = nx.simrank_similarity(G, source=0) + >>> np.array([sim[0][v] for v in G]) + array([1., 0.]) + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/SimRank + .. [2] G. Jeh and J. Widom. + "SimRank: a measure of structural-context similarity", + In KDD'02: Proceedings of the Eighth ACM SIGKDD + International Conference on Knowledge Discovery and Data Mining, + pp. 538--543. ACM Press, 2002. + """ + import numpy as np + + nodelist = list(G) + if source is not None: + if source not in nodelist: + raise nx.NodeNotFound(f"Source node {source} not in G") + else: + s_indx = nodelist.index(source) + else: + s_indx = None + + if target is not None: + if target not in nodelist: + raise nx.NodeNotFound(f"Target node {target} not in G") + else: + t_indx = nodelist.index(target) + else: + t_indx = None + + x = _simrank_similarity_numpy( + G, s_indx, t_indx, importance_factor, max_iterations, tolerance + ) + + if isinstance(x, np.ndarray): + if x.ndim == 1: + return dict(zip(G, x.tolist())) + # else x.ndim == 2 + return {u: dict(zip(G, row)) for u, row in zip(G, x.tolist())} + return float(x) + + +def _simrank_similarity_python( + G, + source=None, + target=None, + importance_factor=0.9, + max_iterations=1000, + tolerance=1e-4, +): + """Returns the SimRank similarity of nodes in the graph ``G``. + + This pure Python version is provided for pedagogical purposes. + + Examples + -------- + >>> G = nx.cycle_graph(2) + >>> nx.similarity._simrank_similarity_python(G) + {0: {0: 1, 1: 0.0}, 1: {0: 0.0, 1: 1}} + >>> nx.similarity._simrank_similarity_python(G, source=0) + {0: 1, 1: 0.0} + >>> nx.similarity._simrank_similarity_python(G, source=0, target=0) + 1 + """ + # build up our similarity adjacency dictionary output + newsim = {u: {v: 1 if u == v else 0 for v in G} for u in G} + + # These functions compute the update to the similarity value of the nodes + # `u` and `v` with respect to the previous similarity values. + def avg_sim(s): + return sum(newsim[w][x] for (w, x) in s) / len(s) if s else 0.0 + + Gadj = G.pred if G.is_directed() else G.adj + + def sim(u, v): + return importance_factor * avg_sim(list(product(Gadj[u], Gadj[v]))) + + for its in range(max_iterations): + oldsim = newsim + newsim = {u: {v: sim(u, v) if u != v else 1 for v in G} for u in G} + is_close = all( + all( + abs(newsim[u][v] - old) <= tolerance * (1 + abs(old)) + for v, old in nbrs.items() + ) + for u, nbrs in oldsim.items() + ) + if is_close: + break + + if its + 1 == max_iterations: + raise nx.ExceededMaxIterations( + f"simrank did not converge after {max_iterations} iterations." + ) + + if source is not None and target is not None: + return newsim[source][target] + if source is not None: + return newsim[source] + return newsim + + +def _simrank_similarity_numpy( + G, + source=None, + target=None, + importance_factor=0.9, + max_iterations=1000, + tolerance=1e-4, +): + """Calculate SimRank of nodes in ``G`` using matrices with ``numpy``. + + The SimRank algorithm for determining node similarity is defined in + [1]_. + + Parameters + ---------- + G : NetworkX graph + A NetworkX graph + + source : node + If this is specified, the returned dictionary maps each node + ``v`` in the graph to the similarity between ``source`` and + ``v``. + + target : node + If both ``source`` and ``target`` are specified, the similarity + value between ``source`` and ``target`` is returned. If + ``target`` is specified but ``source`` is not, this argument is + ignored. + + importance_factor : float + The relative importance of indirect neighbors with respect to + direct neighbors. + + max_iterations : integer + Maximum number of iterations. + + tolerance : float + Error tolerance used to check convergence. When an iteration of + the algorithm finds that no similarity value changes more than + this amount, the algorithm halts. + + Returns + ------- + similarity : numpy array or float + If ``source`` and ``target`` are both ``None``, this returns a + 2D array containing SimRank scores of the nodes. + + If ``source`` is not ``None`` but ``target`` is, this returns an + 1D array containing SimRank scores of ``source`` and that + node. + + If neither ``source`` nor ``target`` is ``None``, this returns + the similarity value for the given pair of nodes. + + Examples + -------- + >>> G = nx.cycle_graph(2) + >>> nx.similarity._simrank_similarity_numpy(G) + array([[1., 0.], + [0., 1.]]) + >>> nx.similarity._simrank_similarity_numpy(G, source=0) + array([1., 0.]) + >>> nx.similarity._simrank_similarity_numpy(G, source=0, target=0) + 1.0 + + References + ---------- + .. [1] G. Jeh and J. Widom. + "SimRank: a measure of structural-context similarity", + In KDD'02: Proceedings of the Eighth ACM SIGKDD + International Conference on Knowledge Discovery and Data Mining, + pp. 538--543. ACM Press, 2002. + """ + # This algorithm follows roughly + # + # S = max{C * (A.T * S * A), I} + # + # where C is the importance factor, A is the column normalized + # adjacency matrix, and I is the identity matrix. + import numpy as np + + adjacency_matrix = nx.to_numpy_array(G) + + # column-normalize the ``adjacency_matrix`` + s = np.array(adjacency_matrix.sum(axis=0)) + s[s == 0] = 1 + adjacency_matrix /= s # adjacency_matrix.sum(axis=0) + + newsim = np.eye(len(G), dtype=np.float64) + for its in range(max_iterations): + prevsim = newsim.copy() + newsim = importance_factor * ((adjacency_matrix.T @ prevsim) @ adjacency_matrix) + np.fill_diagonal(newsim, 1.0) + + if np.allclose(prevsim, newsim, atol=tolerance): + break + + if its + 1 == max_iterations: + raise nx.ExceededMaxIterations( + f"simrank did not converge after {max_iterations} iterations." + ) + + if source is not None and target is not None: + return float(newsim[source, target]) + if source is not None: + return newsim[source] + return newsim + + +@nx._dispatchable(edge_attrs="weight") +def panther_similarity( + G, source, k=5, path_length=5, c=0.5, delta=0.1, eps=None, weight="weight" +): + r"""Returns the Panther similarity of nodes in the graph `G` to node ``v``. + + Panther is a similarity metric that says "two objects are considered + to be similar if they frequently appear on the same paths." [1]_. + + Parameters + ---------- + G : NetworkX graph + A NetworkX graph + source : node + Source node for which to find the top `k` similar other nodes + k : int (default = 5) + The number of most similar nodes to return. + path_length : int (default = 5) + How long the randomly generated paths should be (``T`` in [1]_) + c : float (default = 0.5) + A universal positive constant used to scale the number + of sample random paths to generate. + delta : float (default = 0.1) + The probability that the similarity $S$ is not an epsilon-approximation to (R, phi), + where $R$ is the number of random paths and $\phi$ is the probability + that an element sampled from a set $A \subseteq D$, where $D$ is the domain. + eps : float or None (default = None) + The error bound. Per [1]_, a good value is ``sqrt(1/|E|)``. Therefore, + if no value is provided, the recommended computed value will be used. + weight : string or None, optional (default="weight") + The name of an edge attribute that holds the numerical value + used as a weight. If None then each edge has weight 1. + + Returns + ------- + similarity : dictionary + Dictionary of nodes to similarity scores (as floats). Note: + the self-similarity (i.e., ``v``) will not be included in + the returned dictionary. So, for ``k = 5``, a dictionary of + top 4 nodes and their similarity scores will be returned. + + Raises + ------ + NetworkXUnfeasible + If `source` is an isolated node. + + NodeNotFound + If `source` is not in `G`. + + Notes + ----- + The isolated nodes in `G` are ignored. + + Examples + -------- + >>> G = nx.star_graph(10) + >>> sim = nx.panther_similarity(G, 0) + + References + ---------- + .. [1] Zhang, J., Tang, J., Ma, C., Tong, H., Jing, Y., & Li, J. + Panther: Fast top-k similarity search on large networks. + In Proceedings of the ACM SIGKDD International Conference + on Knowledge Discovery and Data Mining (Vol. 2015-August, pp. 1445–1454). + Association for Computing Machinery. https://doi.org/10.1145/2783258.2783267. + """ + import numpy as np + + if source not in G: + raise nx.NodeNotFound(f"Source node {source} not in G") + + isolates = set(nx.isolates(G)) + + if source in isolates: + raise nx.NetworkXUnfeasible( + f"Panther similarity is not defined for the isolated source node {source}." + ) + + G = G.subgraph([node for node in G.nodes if node not in isolates]).copy() + + num_nodes = G.number_of_nodes() + if num_nodes < k: + warnings.warn( + f"Number of nodes is {num_nodes}, but requested k is {k}. " + "Setting k to number of nodes." + ) + k = num_nodes + # According to [1], they empirically determined + # a good value for ``eps`` to be sqrt( 1 / |E| ) + if eps is None: + eps = np.sqrt(1.0 / G.number_of_edges()) + + inv_node_map = {name: index for index, name in enumerate(G.nodes)} + node_map = np.array(G) + + # Calculate the sample size ``R`` for how many paths + # to randomly generate + t_choose_2 = math.comb(path_length, 2) + sample_size = int((c / eps**2) * (np.log2(t_choose_2) + 1 + np.log(1 / delta))) + index_map = {} + _ = list( + generate_random_paths( + G, sample_size, path_length=path_length, index_map=index_map, weight=weight + ) + ) + S = np.zeros(num_nodes) + + inv_sample_size = 1 / sample_size + + source_paths = set(index_map[source]) + + # Calculate the path similarities + # between ``source`` (v) and ``node`` (v_j) + # using our inverted index mapping of + # vertices to paths + for node, paths in index_map.items(): + # Only consider paths where both + # ``node`` and ``source`` are present + common_paths = source_paths.intersection(paths) + S[inv_node_map[node]] = len(common_paths) * inv_sample_size + + # Retrieve top ``k`` similar + # Note: the below performed anywhere from 4-10x faster + # (depending on input sizes) vs the equivalent ``np.argsort(S)[::-1]`` + top_k_unsorted = np.argpartition(S, -k)[-k:] + top_k_sorted = top_k_unsorted[np.argsort(S[top_k_unsorted])][::-1] + + # Add back the similarity scores + top_k_with_val = dict( + zip(node_map[top_k_sorted].tolist(), S[top_k_sorted].tolist()) + ) + + # Remove the self-similarity + top_k_with_val.pop(source, None) + return top_k_with_val + + +@np_random_state(5) +@nx._dispatchable(edge_attrs="weight") +def generate_random_paths( + G, sample_size, path_length=5, index_map=None, weight="weight", seed=None +): + """Randomly generate `sample_size` paths of length `path_length`. + + Parameters + ---------- + G : NetworkX graph + A NetworkX graph + sample_size : integer + The number of paths to generate. This is ``R`` in [1]_. + path_length : integer (default = 5) + The maximum size of the path to randomly generate. + This is ``T`` in [1]_. According to the paper, ``T >= 5`` is + recommended. + index_map : dictionary, optional + If provided, this will be populated with the inverted + index of nodes mapped to the set of generated random path + indices within ``paths``. + weight : string or None, optional (default="weight") + The name of an edge attribute that holds the numerical value + used as a weight. If None then each edge has weight 1. + seed : integer, random_state, or None (default) + Indicator of random number generation state. + See :ref:`Randomness<randomness>`. + + Returns + ------- + paths : generator of lists + Generator of `sample_size` paths each with length `path_length`. + + Examples + -------- + Note that the return value is the list of paths: + + >>> G = nx.star_graph(3) + >>> random_path = nx.generate_random_paths(G, 2) + + By passing a dictionary into `index_map`, it will build an + inverted index mapping of nodes to the paths in which that node is present: + + >>> G = nx.star_graph(3) + >>> index_map = {} + >>> random_path = nx.generate_random_paths(G, 3, index_map=index_map) + >>> paths_containing_node_0 = [ + ... random_path[path_idx] for path_idx in index_map.get(0, []) + ... ] + + References + ---------- + .. [1] Zhang, J., Tang, J., Ma, C., Tong, H., Jing, Y., & Li, J. + Panther: Fast top-k similarity search on large networks. + In Proceedings of the ACM SIGKDD International Conference + on Knowledge Discovery and Data Mining (Vol. 2015-August, pp. 1445–1454). + Association for Computing Machinery. https://doi.org/10.1145/2783258.2783267. + """ + import numpy as np + + randint_fn = ( + seed.integers if isinstance(seed, np.random.Generator) else seed.randint + ) + + # Calculate transition probabilities between + # every pair of vertices according to Eq. (3) + adj_mat = nx.to_numpy_array(G, weight=weight) + inv_row_sums = np.reciprocal(adj_mat.sum(axis=1)).reshape(-1, 1) + transition_probabilities = adj_mat * inv_row_sums + + node_map = list(G) + num_nodes = G.number_of_nodes() + + for path_index in range(sample_size): + # Sample current vertex v = v_i uniformly at random + node_index = randint_fn(num_nodes) + node = node_map[node_index] + + # Add v into p_r and add p_r into the path set + # of v, i.e., P_v + path = [node] + + # Build the inverted index (P_v) of vertices to paths + if index_map is not None: + if node in index_map: + index_map[node].add(path_index) + else: + index_map[node] = {path_index} + + starting_index = node_index + for _ in range(path_length): + # Randomly sample a neighbor (v_j) according + # to transition probabilities from ``node`` (v) to its neighbors + nbr_index = seed.choice( + num_nodes, p=transition_probabilities[starting_index] + ) + + # Set current vertex (v = v_j) + starting_index = nbr_index + + # Add v into p_r + nbr_node = node_map[nbr_index] + path.append(nbr_node) + + # Add p_r into P_v + if index_map is not None: + if nbr_node in index_map: + index_map[nbr_node].add(path_index) + else: + index_map[nbr_node] = {path_index} + + yield path |