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author | S. Solomon Darnell | 2025-03-28 21:52:21 -0500 |
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committer | S. Solomon Darnell | 2025-03-28 21:52:21 -0500 |
commit | 4a52a71956a8d46fcb7294ac71734504bb09bcc2 (patch) | |
tree | ee3dc5af3b6313e921cd920906356f5d4febc4ed /.venv/lib/python3.12/site-packages/networkx/algorithms/components | |
parent | cc961e04ba734dd72309fb548a2f97d67d578813 (diff) | |
download | gn-ai-master.tar.gz |
Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/components')
14 files changed, 2150 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/__init__.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/__init__.py new file mode 100644 index 00000000..f9ae2cab --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/__init__.py @@ -0,0 +1,6 @@ +from .connected import * +from .strongly_connected import * +from .weakly_connected import * +from .attracting import * +from .biconnected import * +from .semiconnected import * diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/attracting.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/attracting.py new file mode 100644 index 00000000..3d77cd93 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/attracting.py @@ -0,0 +1,115 @@ +"""Attracting components.""" + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +__all__ = [ + "number_attracting_components", + "attracting_components", + "is_attracting_component", +] + + +@not_implemented_for("undirected") +@nx._dispatchable +def attracting_components(G): + """Generates the attracting components in `G`. + + An attracting component in a directed graph `G` is a strongly connected + component with the property that a random walker on the graph will never + leave the component, once it enters the component. + + The nodes in attracting components can also be thought of as recurrent + nodes. If a random walker enters the attractor containing the node, then + the node will be visited infinitely often. + + To obtain induced subgraphs on each component use: + ``(G.subgraph(c).copy() for c in attracting_components(G))`` + + Parameters + ---------- + G : DiGraph, MultiDiGraph + The graph to be analyzed. + + Returns + ------- + attractors : generator of sets + A generator of sets of nodes, one for each attracting component of G. + + Raises + ------ + NetworkXNotImplemented + If the input graph is undirected. + + See Also + -------- + number_attracting_components + is_attracting_component + + """ + scc = list(nx.strongly_connected_components(G)) + cG = nx.condensation(G, scc) + for n in cG: + if cG.out_degree(n) == 0: + yield scc[n] + + +@not_implemented_for("undirected") +@nx._dispatchable +def number_attracting_components(G): + """Returns the number of attracting components in `G`. + + Parameters + ---------- + G : DiGraph, MultiDiGraph + The graph to be analyzed. + + Returns + ------- + n : int + The number of attracting components in G. + + Raises + ------ + NetworkXNotImplemented + If the input graph is undirected. + + See Also + -------- + attracting_components + is_attracting_component + + """ + return sum(1 for ac in attracting_components(G)) + + +@not_implemented_for("undirected") +@nx._dispatchable +def is_attracting_component(G): + """Returns True if `G` consists of a single attracting component. + + Parameters + ---------- + G : DiGraph, MultiDiGraph + The graph to be analyzed. + + Returns + ------- + attracting : bool + True if `G` has a single attracting component. Otherwise, False. + + Raises + ------ + NetworkXNotImplemented + If the input graph is undirected. + + See Also + -------- + attracting_components + number_attracting_components + + """ + ac = list(attracting_components(G)) + if len(ac) == 1: + return len(ac[0]) == len(G) + return False diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/biconnected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/biconnected.py new file mode 100644 index 00000000..fd0f3865 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/biconnected.py @@ -0,0 +1,394 @@ +"""Biconnected components and articulation points.""" + +from itertools import chain + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +__all__ = [ + "biconnected_components", + "biconnected_component_edges", + "is_biconnected", + "articulation_points", +] + + +@not_implemented_for("directed") +@nx._dispatchable +def is_biconnected(G): + """Returns True if the graph is biconnected, False otherwise. + + A graph is biconnected if, and only if, it cannot be disconnected by + removing only one node (and all edges incident on that node). If + removing a node increases the number of disconnected components + in the graph, that node is called an articulation point, or cut + vertex. A biconnected graph has no articulation points. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Returns + ------- + biconnected : bool + True if the graph is biconnected, False otherwise. + + Raises + ------ + NetworkXNotImplemented + If the input graph is not undirected. + + Examples + -------- + >>> G = nx.path_graph(4) + >>> print(nx.is_biconnected(G)) + False + >>> G.add_edge(0, 3) + >>> print(nx.is_biconnected(G)) + True + + See Also + -------- + biconnected_components + articulation_points + biconnected_component_edges + is_strongly_connected + is_weakly_connected + is_connected + is_semiconnected + + Notes + ----- + The algorithm to find articulation points and biconnected + components is implemented using a non-recursive depth-first-search + (DFS) that keeps track of the highest level that back edges reach + in the DFS tree. A node `n` is an articulation point if, and only + if, there exists a subtree rooted at `n` such that there is no + back edge from any successor of `n` that links to a predecessor of + `n` in the DFS tree. By keeping track of all the edges traversed + by the DFS we can obtain the biconnected components because all + edges of a bicomponent will be traversed consecutively between + articulation points. + + References + ---------- + .. [1] Hopcroft, J.; Tarjan, R. (1973). + "Efficient algorithms for graph manipulation". + Communications of the ACM 16: 372–378. doi:10.1145/362248.362272 + + """ + bccs = biconnected_components(G) + try: + bcc = next(bccs) + except StopIteration: + # No bicomponents (empty graph?) + return False + try: + next(bccs) + except StopIteration: + # Only one bicomponent + return len(bcc) == len(G) + else: + # Multiple bicomponents + return False + + +@not_implemented_for("directed") +@nx._dispatchable +def biconnected_component_edges(G): + """Returns a generator of lists of edges, one list for each biconnected + component of the input graph. + + Biconnected components are maximal subgraphs such that the removal of a + node (and all edges incident on that node) will not disconnect the + subgraph. Note that nodes may be part of more than one biconnected + component. Those nodes are articulation points, or cut vertices. + However, each edge belongs to one, and only one, biconnected component. + + Notice that by convention a dyad is considered a biconnected component. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Returns + ------- + edges : generator of lists + Generator of lists of edges, one list for each bicomponent. + + Raises + ------ + NetworkXNotImplemented + If the input graph is not undirected. + + Examples + -------- + >>> G = nx.barbell_graph(4, 2) + >>> print(nx.is_biconnected(G)) + False + >>> bicomponents_edges = list(nx.biconnected_component_edges(G)) + >>> len(bicomponents_edges) + 5 + >>> G.add_edge(2, 8) + >>> print(nx.is_biconnected(G)) + True + >>> bicomponents_edges = list(nx.biconnected_component_edges(G)) + >>> len(bicomponents_edges) + 1 + + See Also + -------- + is_biconnected, + biconnected_components, + articulation_points, + + Notes + ----- + The algorithm to find articulation points and biconnected + components is implemented using a non-recursive depth-first-search + (DFS) that keeps track of the highest level that back edges reach + in the DFS tree. A node `n` is an articulation point if, and only + if, there exists a subtree rooted at `n` such that there is no + back edge from any successor of `n` that links to a predecessor of + `n` in the DFS tree. By keeping track of all the edges traversed + by the DFS we can obtain the biconnected components because all + edges of a bicomponent will be traversed consecutively between + articulation points. + + References + ---------- + .. [1] Hopcroft, J.; Tarjan, R. (1973). + "Efficient algorithms for graph manipulation". + Communications of the ACM 16: 372–378. doi:10.1145/362248.362272 + + """ + yield from _biconnected_dfs(G, components=True) + + +@not_implemented_for("directed") +@nx._dispatchable +def biconnected_components(G): + """Returns a generator of sets of nodes, one set for each biconnected + component of the graph + + Biconnected components are maximal subgraphs such that the removal of a + node (and all edges incident on that node) will not disconnect the + subgraph. Note that nodes may be part of more than one biconnected + component. Those nodes are articulation points, or cut vertices. The + removal of articulation points will increase the number of connected + components of the graph. + + Notice that by convention a dyad is considered a biconnected component. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Returns + ------- + nodes : generator + Generator of sets of nodes, one set for each biconnected component. + + Raises + ------ + NetworkXNotImplemented + If the input graph is not undirected. + + Examples + -------- + >>> G = nx.lollipop_graph(5, 1) + >>> print(nx.is_biconnected(G)) + False + >>> bicomponents = list(nx.biconnected_components(G)) + >>> len(bicomponents) + 2 + >>> G.add_edge(0, 5) + >>> print(nx.is_biconnected(G)) + True + >>> bicomponents = list(nx.biconnected_components(G)) + >>> len(bicomponents) + 1 + + You can generate a sorted list of biconnected components, largest + first, using sort. + + >>> G.remove_edge(0, 5) + >>> [len(c) for c in sorted(nx.biconnected_components(G), key=len, reverse=True)] + [5, 2] + + If you only want the largest connected component, it's more + efficient to use max instead of sort. + + >>> Gc = max(nx.biconnected_components(G), key=len) + + To create the components as subgraphs use: + ``(G.subgraph(c).copy() for c in biconnected_components(G))`` + + See Also + -------- + is_biconnected + articulation_points + biconnected_component_edges + k_components : this function is a special case where k=2 + bridge_components : similar to this function, but is defined using + 2-edge-connectivity instead of 2-node-connectivity. + + Notes + ----- + The algorithm to find articulation points and biconnected + components is implemented using a non-recursive depth-first-search + (DFS) that keeps track of the highest level that back edges reach + in the DFS tree. A node `n` is an articulation point if, and only + if, there exists a subtree rooted at `n` such that there is no + back edge from any successor of `n` that links to a predecessor of + `n` in the DFS tree. By keeping track of all the edges traversed + by the DFS we can obtain the biconnected components because all + edges of a bicomponent will be traversed consecutively between + articulation points. + + References + ---------- + .. [1] Hopcroft, J.; Tarjan, R. (1973). + "Efficient algorithms for graph manipulation". + Communications of the ACM 16: 372–378. doi:10.1145/362248.362272 + + """ + for comp in _biconnected_dfs(G, components=True): + yield set(chain.from_iterable(comp)) + + +@not_implemented_for("directed") +@nx._dispatchable +def articulation_points(G): + """Yield the articulation points, or cut vertices, of a graph. + + An articulation point or cut vertex is any node whose removal (along with + all its incident edges) increases the number of connected components of + a graph. An undirected connected graph without articulation points is + biconnected. Articulation points belong to more than one biconnected + component of a graph. + + Notice that by convention a dyad is considered a biconnected component. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Yields + ------ + node + An articulation point in the graph. + + Raises + ------ + NetworkXNotImplemented + If the input graph is not undirected. + + Examples + -------- + + >>> G = nx.barbell_graph(4, 2) + >>> print(nx.is_biconnected(G)) + False + >>> len(list(nx.articulation_points(G))) + 4 + >>> G.add_edge(2, 8) + >>> print(nx.is_biconnected(G)) + True + >>> len(list(nx.articulation_points(G))) + 0 + + See Also + -------- + is_biconnected + biconnected_components + biconnected_component_edges + + Notes + ----- + The algorithm to find articulation points and biconnected + components is implemented using a non-recursive depth-first-search + (DFS) that keeps track of the highest level that back edges reach + in the DFS tree. A node `n` is an articulation point if, and only + if, there exists a subtree rooted at `n` such that there is no + back edge from any successor of `n` that links to a predecessor of + `n` in the DFS tree. By keeping track of all the edges traversed + by the DFS we can obtain the biconnected components because all + edges of a bicomponent will be traversed consecutively between + articulation points. + + References + ---------- + .. [1] Hopcroft, J.; Tarjan, R. (1973). + "Efficient algorithms for graph manipulation". + Communications of the ACM 16: 372–378. doi:10.1145/362248.362272 + + """ + seen = set() + for articulation in _biconnected_dfs(G, components=False): + if articulation not in seen: + seen.add(articulation) + yield articulation + + +@not_implemented_for("directed") +def _biconnected_dfs(G, components=True): + # depth-first search algorithm to generate articulation points + # and biconnected components + visited = set() + for start in G: + if start in visited: + continue + discovery = {start: 0} # time of first discovery of node during search + low = {start: 0} + root_children = 0 + visited.add(start) + edge_stack = [] + stack = [(start, start, iter(G[start]))] + edge_index = {} + while stack: + grandparent, parent, children = stack[-1] + try: + child = next(children) + if grandparent == child: + continue + if child in visited: + if discovery[child] <= discovery[parent]: # back edge + low[parent] = min(low[parent], discovery[child]) + if components: + edge_index[parent, child] = len(edge_stack) + edge_stack.append((parent, child)) + else: + low[child] = discovery[child] = len(discovery) + visited.add(child) + stack.append((parent, child, iter(G[child]))) + if components: + edge_index[parent, child] = len(edge_stack) + edge_stack.append((parent, child)) + + except StopIteration: + stack.pop() + if len(stack) > 1: + if low[parent] >= discovery[grandparent]: + if components: + ind = edge_index[grandparent, parent] + yield edge_stack[ind:] + del edge_stack[ind:] + + else: + yield grandparent + low[grandparent] = min(low[parent], low[grandparent]) + elif stack: # length 1 so grandparent is root + root_children += 1 + if components: + ind = edge_index[grandparent, parent] + yield edge_stack[ind:] + del edge_stack[ind:] + if not components: + # root node is articulation point if it has more than 1 child + if root_children > 1: + yield start diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py new file mode 100644 index 00000000..ebe0d8c1 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py @@ -0,0 +1,216 @@ +"""Connected components.""" + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +from ...utils import arbitrary_element + +__all__ = [ + "number_connected_components", + "connected_components", + "is_connected", + "node_connected_component", +] + + +@not_implemented_for("directed") +@nx._dispatchable +def connected_components(G): + """Generate connected components. + + Parameters + ---------- + G : NetworkX graph + An undirected graph + + Returns + ------- + comp : generator of sets + A generator of sets of nodes, one for each component of G. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + Generate a sorted list of connected components, largest first. + + >>> G = nx.path_graph(4) + >>> nx.add_path(G, [10, 11, 12]) + >>> [len(c) for c in sorted(nx.connected_components(G), key=len, reverse=True)] + [4, 3] + + If you only want the largest connected component, it's more + efficient to use max instead of sort. + + >>> largest_cc = max(nx.connected_components(G), key=len) + + To create the induced subgraph of each component use: + + >>> S = [G.subgraph(c).copy() for c in nx.connected_components(G)] + + See Also + -------- + strongly_connected_components + weakly_connected_components + + Notes + ----- + For undirected graphs only. + + """ + seen = set() + n = len(G) + for v in G: + if v not in seen: + c = _plain_bfs(G, n, v) + seen.update(c) + yield c + + +@not_implemented_for("directed") +@nx._dispatchable +def number_connected_components(G): + """Returns the number of connected components. + + Parameters + ---------- + G : NetworkX graph + An undirected graph. + + Returns + ------- + n : integer + Number of connected components + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.Graph([(0, 1), (1, 2), (5, 6), (3, 4)]) + >>> nx.number_connected_components(G) + 3 + + See Also + -------- + connected_components + number_weakly_connected_components + number_strongly_connected_components + + Notes + ----- + For undirected graphs only. + + """ + return sum(1 for cc in connected_components(G)) + + +@not_implemented_for("directed") +@nx._dispatchable +def is_connected(G): + """Returns True if the graph is connected, False otherwise. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Returns + ------- + connected : bool + True if the graph is connected, false otherwise. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.path_graph(4) + >>> print(nx.is_connected(G)) + True + + See Also + -------- + is_strongly_connected + is_weakly_connected + is_semiconnected + is_biconnected + connected_components + + Notes + ----- + For undirected graphs only. + + """ + n = len(G) + if n == 0: + raise nx.NetworkXPointlessConcept( + "Connectivity is undefined for the null graph." + ) + return sum(1 for node in _plain_bfs(G, n, arbitrary_element(G))) == len(G) + + +@not_implemented_for("directed") +@nx._dispatchable +def node_connected_component(G, n): + """Returns the set of nodes in the component of graph containing node n. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + n : node label + A node in G + + Returns + ------- + comp : set + A set of nodes in the component of G containing node n. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.Graph([(0, 1), (1, 2), (5, 6), (3, 4)]) + >>> nx.node_connected_component(G, 0) # nodes of component that contains node 0 + {0, 1, 2} + + See Also + -------- + connected_components + + Notes + ----- + For undirected graphs only. + + """ + return _plain_bfs(G, len(G), n) + + +def _plain_bfs(G, n, source): + """A fast BFS node generator""" + adj = G._adj + seen = {source} + nextlevel = [source] + while nextlevel: + thislevel = nextlevel + nextlevel = [] + for v in thislevel: + for w in adj[v]: + if w not in seen: + seen.add(w) + nextlevel.append(w) + if len(seen) == n: + return seen + return seen diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/semiconnected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/semiconnected.py new file mode 100644 index 00000000..9ca5d762 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/semiconnected.py @@ -0,0 +1,71 @@ +"""Semiconnectedness.""" + +import networkx as nx +from networkx.utils import not_implemented_for, pairwise + +__all__ = ["is_semiconnected"] + + +@not_implemented_for("undirected") +@nx._dispatchable +def is_semiconnected(G): + r"""Returns True if the graph is semiconnected, False otherwise. + + A graph is semiconnected if and only if for any pair of nodes, either one + is reachable from the other, or they are mutually reachable. + + This function uses a theorem that states that a DAG is semiconnected + if for any topological sort, for node $v_n$ in that sort, there is an + edge $(v_i, v_{i+1})$. That allows us to check if a non-DAG `G` is + semiconnected by condensing the graph: i.e. constructing a new graph `H` + with nodes being the strongly connected components of `G`, and edges + (scc_1, scc_2) if there is a edge $(v_1, v_2)$ in `G` for some + $v_1 \in scc_1$ and $v_2 \in scc_2$. That results in a DAG, so we compute + the topological sort of `H` and check if for every $n$ there is an edge + $(scc_n, scc_{n+1})$. + + Parameters + ---------- + G : NetworkX graph + A directed graph. + + Returns + ------- + semiconnected : bool + True if the graph is semiconnected, False otherwise. + + Raises + ------ + NetworkXNotImplemented + If the input graph is undirected. + + NetworkXPointlessConcept + If the graph is empty. + + Examples + -------- + >>> G = nx.path_graph(4, create_using=nx.DiGraph()) + >>> print(nx.is_semiconnected(G)) + True + >>> G = nx.DiGraph([(1, 2), (3, 2)]) + >>> print(nx.is_semiconnected(G)) + False + + See Also + -------- + is_strongly_connected + is_weakly_connected + is_connected + is_biconnected + """ + if len(G) == 0: + raise nx.NetworkXPointlessConcept( + "Connectivity is undefined for the null graph." + ) + + if not nx.is_weakly_connected(G): + return False + + H = nx.condensation(G) + + return all(H.has_edge(u, v) for u, v in pairwise(nx.topological_sort(H))) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/strongly_connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/strongly_connected.py new file mode 100644 index 00000000..393728ff --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/strongly_connected.py @@ -0,0 +1,351 @@ +"""Strongly connected components.""" + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +__all__ = [ + "number_strongly_connected_components", + "strongly_connected_components", + "is_strongly_connected", + "kosaraju_strongly_connected_components", + "condensation", +] + + +@not_implemented_for("undirected") +@nx._dispatchable +def strongly_connected_components(G): + """Generate nodes in strongly connected components of graph. + + Parameters + ---------- + G : NetworkX Graph + A directed graph. + + Returns + ------- + comp : generator of sets + A generator of sets of nodes, one for each strongly connected + component of G. + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + Generate a sorted list of strongly connected components, largest first. + + >>> G = nx.cycle_graph(4, create_using=nx.DiGraph()) + >>> nx.add_cycle(G, [10, 11, 12]) + >>> [ + ... len(c) + ... for c in sorted(nx.strongly_connected_components(G), key=len, reverse=True) + ... ] + [4, 3] + + If you only want the largest component, it's more efficient to + use max instead of sort. + + >>> largest = max(nx.strongly_connected_components(G), key=len) + + See Also + -------- + connected_components + weakly_connected_components + kosaraju_strongly_connected_components + + Notes + ----- + Uses Tarjan's algorithm[1]_ with Nuutila's modifications[2]_. + Nonrecursive version of algorithm. + + References + ---------- + .. [1] Depth-first search and linear graph algorithms, R. Tarjan + SIAM Journal of Computing 1(2):146-160, (1972). + + .. [2] On finding the strongly connected components in a directed graph. + E. Nuutila and E. Soisalon-Soinen + Information Processing Letters 49(1): 9-14, (1994).. + + """ + preorder = {} + lowlink = {} + scc_found = set() + scc_queue = [] + i = 0 # Preorder counter + neighbors = {v: iter(G[v]) for v in G} + for source in G: + if source not in scc_found: + queue = [source] + while queue: + v = queue[-1] + if v not in preorder: + i = i + 1 + preorder[v] = i + done = True + for w in neighbors[v]: + if w not in preorder: + queue.append(w) + done = False + break + if done: + lowlink[v] = preorder[v] + for w in G[v]: + if w not in scc_found: + if preorder[w] > preorder[v]: + lowlink[v] = min([lowlink[v], lowlink[w]]) + else: + lowlink[v] = min([lowlink[v], preorder[w]]) + queue.pop() + if lowlink[v] == preorder[v]: + scc = {v} + while scc_queue and preorder[scc_queue[-1]] > preorder[v]: + k = scc_queue.pop() + scc.add(k) + scc_found.update(scc) + yield scc + else: + scc_queue.append(v) + + +@not_implemented_for("undirected") +@nx._dispatchable +def kosaraju_strongly_connected_components(G, source=None): + """Generate nodes in strongly connected components of graph. + + Parameters + ---------- + G : NetworkX Graph + A directed graph. + + Returns + ------- + comp : generator of sets + A generator of sets of nodes, one for each strongly connected + component of G. + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + Generate a sorted list of strongly connected components, largest first. + + >>> G = nx.cycle_graph(4, create_using=nx.DiGraph()) + >>> nx.add_cycle(G, [10, 11, 12]) + >>> [ + ... len(c) + ... for c in sorted( + ... nx.kosaraju_strongly_connected_components(G), key=len, reverse=True + ... ) + ... ] + [4, 3] + + If you only want the largest component, it's more efficient to + use max instead of sort. + + >>> largest = max(nx.kosaraju_strongly_connected_components(G), key=len) + + See Also + -------- + strongly_connected_components + + Notes + ----- + Uses Kosaraju's algorithm. + + """ + post = list(nx.dfs_postorder_nodes(G.reverse(copy=False), source=source)) + + seen = set() + while post: + r = post.pop() + if r in seen: + continue + c = nx.dfs_preorder_nodes(G, r) + new = {v for v in c if v not in seen} + seen.update(new) + yield new + + +@not_implemented_for("undirected") +@nx._dispatchable +def number_strongly_connected_components(G): + """Returns number of strongly connected components in graph. + + Parameters + ---------- + G : NetworkX graph + A directed graph. + + Returns + ------- + n : integer + Number of strongly connected components + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + >>> G = nx.DiGraph( + ... [(0, 1), (1, 2), (2, 0), (2, 3), (4, 5), (3, 4), (5, 6), (6, 3), (6, 7)] + ... ) + >>> nx.number_strongly_connected_components(G) + 3 + + See Also + -------- + strongly_connected_components + number_connected_components + number_weakly_connected_components + + Notes + ----- + For directed graphs only. + """ + return sum(1 for scc in strongly_connected_components(G)) + + +@not_implemented_for("undirected") +@nx._dispatchable +def is_strongly_connected(G): + """Test directed graph for strong connectivity. + + A directed graph is strongly connected if and only if every vertex in + the graph is reachable from every other vertex. + + Parameters + ---------- + G : NetworkX Graph + A directed graph. + + Returns + ------- + connected : bool + True if the graph is strongly connected, False otherwise. + + Examples + -------- + >>> G = nx.DiGraph([(0, 1), (1, 2), (2, 3), (3, 0), (2, 4), (4, 2)]) + >>> nx.is_strongly_connected(G) + True + >>> G.remove_edge(2, 3) + >>> nx.is_strongly_connected(G) + False + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + See Also + -------- + is_weakly_connected + is_semiconnected + is_connected + is_biconnected + strongly_connected_components + + Notes + ----- + For directed graphs only. + """ + if len(G) == 0: + raise nx.NetworkXPointlessConcept( + """Connectivity is undefined for the null graph.""" + ) + + return len(next(strongly_connected_components(G))) == len(G) + + +@not_implemented_for("undirected") +@nx._dispatchable(returns_graph=True) +def condensation(G, scc=None): + """Returns the condensation of G. + + The condensation of G is the graph with each of the strongly connected + components contracted into a single node. + + Parameters + ---------- + G : NetworkX DiGraph + A directed graph. + + scc: list or generator (optional, default=None) + Strongly connected components. If provided, the elements in + `scc` must partition the nodes in `G`. If not provided, it will be + calculated as scc=nx.strongly_connected_components(G). + + Returns + ------- + C : NetworkX DiGraph + The condensation graph C of G. The node labels are integers + corresponding to the index of the component in the list of + strongly connected components of G. C has a graph attribute named + 'mapping' with a dictionary mapping the original nodes to the + nodes in C to which they belong. Each node in C also has a node + attribute 'members' with the set of original nodes in G that + form the SCC that the node in C represents. + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + Contracting two sets of strongly connected nodes into two distinct SCC + using the barbell graph. + + >>> G = nx.barbell_graph(4, 0) + >>> G.remove_edge(3, 4) + >>> G = nx.DiGraph(G) + >>> H = nx.condensation(G) + >>> H.nodes.data() + NodeDataView({0: {'members': {0, 1, 2, 3}}, 1: {'members': {4, 5, 6, 7}}}) + >>> H.graph["mapping"] + {0: 0, 1: 0, 2: 0, 3: 0, 4: 1, 5: 1, 6: 1, 7: 1} + + Contracting a complete graph into one single SCC. + + >>> G = nx.complete_graph(7, create_using=nx.DiGraph) + >>> H = nx.condensation(G) + >>> H.nodes + NodeView((0,)) + >>> H.nodes.data() + NodeDataView({0: {'members': {0, 1, 2, 3, 4, 5, 6}}}) + + Notes + ----- + After contracting all strongly connected components to a single node, + the resulting graph is a directed acyclic graph. + + """ + if scc is None: + scc = nx.strongly_connected_components(G) + mapping = {} + members = {} + C = nx.DiGraph() + # Add mapping dict as graph attribute + C.graph["mapping"] = mapping + if len(G) == 0: + return C + for i, component in enumerate(scc): + members[i] = component + mapping.update((n, i) for n in component) + number_of_components = i + 1 + C.add_nodes_from(range(number_of_components)) + C.add_edges_from( + (mapping[u], mapping[v]) for u, v in G.edges() if mapping[u] != mapping[v] + ) + # Add a list of members (ie original nodes) to each node (ie scc) in C. + nx.set_node_attributes(C, members, "members") + return C diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/__init__.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/__init__.py new file mode 100644 index 00000000..e69de29b --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/__init__.py diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_attracting.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_attracting.py new file mode 100644 index 00000000..336c40dd --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_attracting.py @@ -0,0 +1,70 @@ +import pytest + +import networkx as nx +from networkx import NetworkXNotImplemented + + +class TestAttractingComponents: + @classmethod + def setup_class(cls): + cls.G1 = nx.DiGraph() + cls.G1.add_edges_from( + [ + (5, 11), + (11, 2), + (11, 9), + (11, 10), + (7, 11), + (7, 8), + (8, 9), + (3, 8), + (3, 10), + ] + ) + cls.G2 = nx.DiGraph() + cls.G2.add_edges_from([(0, 1), (0, 2), (1, 1), (1, 2), (2, 1)]) + + cls.G3 = nx.DiGraph() + cls.G3.add_edges_from([(0, 1), (1, 2), (2, 1), (0, 3), (3, 4), (4, 3)]) + + cls.G4 = nx.DiGraph() + + def test_attracting_components(self): + ac = list(nx.attracting_components(self.G1)) + assert {2} in ac + assert {9} in ac + assert {10} in ac + + ac = list(nx.attracting_components(self.G2)) + ac = [tuple(sorted(x)) for x in ac] + assert ac == [(1, 2)] + + ac = list(nx.attracting_components(self.G3)) + ac = [tuple(sorted(x)) for x in ac] + assert (1, 2) in ac + assert (3, 4) in ac + assert len(ac) == 2 + + ac = list(nx.attracting_components(self.G4)) + assert ac == [] + + def test_number_attacting_components(self): + assert nx.number_attracting_components(self.G1) == 3 + assert nx.number_attracting_components(self.G2) == 1 + assert nx.number_attracting_components(self.G3) == 2 + assert nx.number_attracting_components(self.G4) == 0 + + def test_is_attracting_component(self): + assert not nx.is_attracting_component(self.G1) + assert not nx.is_attracting_component(self.G2) + assert not nx.is_attracting_component(self.G3) + g2 = self.G3.subgraph([1, 2]) + assert nx.is_attracting_component(g2) + assert not nx.is_attracting_component(self.G4) + + def test_connected_raise(self): + G = nx.Graph() + with pytest.raises(NetworkXNotImplemented): + next(nx.attracting_components(G)) + pytest.raises(NetworkXNotImplemented, nx.number_attracting_components, G) + pytest.raises(NetworkXNotImplemented, nx.is_attracting_component, G) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_biconnected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_biconnected.py new file mode 100644 index 00000000..19d2d883 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_biconnected.py @@ -0,0 +1,248 @@ +import pytest + +import networkx as nx +from networkx import NetworkXNotImplemented + + +def assert_components_edges_equal(x, y): + sx = {frozenset(frozenset(e) for e in c) for c in x} + sy = {frozenset(frozenset(e) for e in c) for c in y} + assert sx == sy + + +def assert_components_equal(x, y): + sx = {frozenset(c) for c in x} + sy = {frozenset(c) for c in y} + assert sx == sy + + +def test_barbell(): + G = nx.barbell_graph(8, 4) + nx.add_path(G, [7, 20, 21, 22]) + nx.add_cycle(G, [22, 23, 24, 25]) + pts = set(nx.articulation_points(G)) + assert pts == {7, 8, 9, 10, 11, 12, 20, 21, 22} + + answer = [ + {12, 13, 14, 15, 16, 17, 18, 19}, + {0, 1, 2, 3, 4, 5, 6, 7}, + {22, 23, 24, 25}, + {11, 12}, + {10, 11}, + {9, 10}, + {8, 9}, + {7, 8}, + {21, 22}, + {20, 21}, + {7, 20}, + ] + assert_components_equal(list(nx.biconnected_components(G)), answer) + + G.add_edge(2, 17) + pts = set(nx.articulation_points(G)) + assert pts == {7, 20, 21, 22} + + +def test_articulation_points_repetitions(): + G = nx.Graph() + G.add_edges_from([(0, 1), (1, 2), (1, 3)]) + assert list(nx.articulation_points(G)) == [1] + + +def test_articulation_points_cycle(): + G = nx.cycle_graph(3) + nx.add_cycle(G, [1, 3, 4]) + pts = set(nx.articulation_points(G)) + assert pts == {1} + + +def test_is_biconnected(): + G = nx.cycle_graph(3) + assert nx.is_biconnected(G) + nx.add_cycle(G, [1, 3, 4]) + assert not nx.is_biconnected(G) + + +def test_empty_is_biconnected(): + G = nx.empty_graph(5) + assert not nx.is_biconnected(G) + G.add_edge(0, 1) + assert not nx.is_biconnected(G) + + +def test_biconnected_components_cycle(): + G = nx.cycle_graph(3) + nx.add_cycle(G, [1, 3, 4]) + answer = [{0, 1, 2}, {1, 3, 4}] + assert_components_equal(list(nx.biconnected_components(G)), answer) + + +def test_biconnected_components1(): + # graph example from + # https://web.archive.org/web/20121229123447/http://www.ibluemojo.com/school/articul_algorithm.html + edges = [ + (0, 1), + (0, 5), + (0, 6), + (0, 14), + (1, 5), + (1, 6), + (1, 14), + (2, 4), + (2, 10), + (3, 4), + (3, 15), + (4, 6), + (4, 7), + (4, 10), + (5, 14), + (6, 14), + (7, 9), + (8, 9), + (8, 12), + (8, 13), + (10, 15), + (11, 12), + (11, 13), + (12, 13), + ] + G = nx.Graph(edges) + pts = set(nx.articulation_points(G)) + assert pts == {4, 6, 7, 8, 9} + comps = list(nx.biconnected_component_edges(G)) + answer = [ + [(3, 4), (15, 3), (10, 15), (10, 4), (2, 10), (4, 2)], + [(13, 12), (13, 8), (11, 13), (12, 11), (8, 12)], + [(9, 8)], + [(7, 9)], + [(4, 7)], + [(6, 4)], + [(14, 0), (5, 1), (5, 0), (14, 5), (14, 1), (6, 14), (6, 0), (1, 6), (0, 1)], + ] + assert_components_edges_equal(comps, answer) + + +def test_biconnected_components2(): + G = nx.Graph() + nx.add_cycle(G, "ABC") + nx.add_cycle(G, "CDE") + nx.add_cycle(G, "FIJHG") + nx.add_cycle(G, "GIJ") + G.add_edge("E", "G") + comps = list(nx.biconnected_component_edges(G)) + answer = [ + [ + tuple("GF"), + tuple("FI"), + tuple("IG"), + tuple("IJ"), + tuple("JG"), + tuple("JH"), + tuple("HG"), + ], + [tuple("EG")], + [tuple("CD"), tuple("DE"), tuple("CE")], + [tuple("AB"), tuple("BC"), tuple("AC")], + ] + assert_components_edges_equal(comps, answer) + + +def test_biconnected_davis(): + D = nx.davis_southern_women_graph() + bcc = list(nx.biconnected_components(D))[0] + assert set(D) == bcc # All nodes in a giant bicomponent + # So no articulation points + assert len(list(nx.articulation_points(D))) == 0 + + +def test_biconnected_karate(): + K = nx.karate_club_graph() + answer = [ + { + 0, + 1, + 2, + 3, + 7, + 8, + 9, + 12, + 13, + 14, + 15, + 17, + 18, + 19, + 20, + 21, + 22, + 23, + 24, + 25, + 26, + 27, + 28, + 29, + 30, + 31, + 32, + 33, + }, + {0, 4, 5, 6, 10, 16}, + {0, 11}, + ] + bcc = list(nx.biconnected_components(K)) + assert_components_equal(bcc, answer) + assert set(nx.articulation_points(K)) == {0} + + +def test_biconnected_eppstein(): + # tests from http://www.ics.uci.edu/~eppstein/PADS/Biconnectivity.py + G1 = nx.Graph( + { + 0: [1, 2, 5], + 1: [0, 5], + 2: [0, 3, 4], + 3: [2, 4, 5, 6], + 4: [2, 3, 5, 6], + 5: [0, 1, 3, 4], + 6: [3, 4], + } + ) + G2 = nx.Graph( + { + 0: [2, 5], + 1: [3, 8], + 2: [0, 3, 5], + 3: [1, 2, 6, 8], + 4: [7], + 5: [0, 2], + 6: [3, 8], + 7: [4], + 8: [1, 3, 6], + } + ) + assert nx.is_biconnected(G1) + assert not nx.is_biconnected(G2) + answer_G2 = [{1, 3, 6, 8}, {0, 2, 5}, {2, 3}, {4, 7}] + bcc = list(nx.biconnected_components(G2)) + assert_components_equal(bcc, answer_G2) + + +def test_null_graph(): + G = nx.Graph() + assert not nx.is_biconnected(G) + assert list(nx.biconnected_components(G)) == [] + assert list(nx.biconnected_component_edges(G)) == [] + assert list(nx.articulation_points(G)) == [] + + +def test_connected_raise(): + DG = nx.DiGraph() + with pytest.raises(NetworkXNotImplemented): + next(nx.biconnected_components(DG)) + with pytest.raises(NetworkXNotImplemented): + next(nx.biconnected_component_edges(DG)) + with pytest.raises(NetworkXNotImplemented): + next(nx.articulation_points(DG)) + pytest.raises(NetworkXNotImplemented, nx.is_biconnected, DG) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_connected.py new file mode 100644 index 00000000..207214c1 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_connected.py @@ -0,0 +1,138 @@ +import pytest + +import networkx as nx +from networkx import NetworkXNotImplemented +from networkx import convert_node_labels_to_integers as cnlti +from networkx.classes.tests import dispatch_interface + + +class TestConnected: + @classmethod + def setup_class(cls): + G1 = cnlti(nx.grid_2d_graph(2, 2), first_label=0, ordering="sorted") + G2 = cnlti(nx.lollipop_graph(3, 3), first_label=4, ordering="sorted") + G3 = cnlti(nx.house_graph(), first_label=10, ordering="sorted") + cls.G = nx.union(G1, G2) + cls.G = nx.union(cls.G, G3) + cls.DG = nx.DiGraph([(1, 2), (1, 3), (2, 3)]) + cls.grid = cnlti(nx.grid_2d_graph(4, 4), first_label=1) + + cls.gc = [] + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2), + (2, 3), + (2, 8), + (3, 4), + (3, 7), + (4, 5), + (5, 3), + (5, 6), + (7, 4), + (7, 6), + (8, 1), + (8, 7), + ] + ) + C = [[3, 4, 5, 7], [1, 2, 8], [6]] + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)]) + C = [[2, 3, 4], [1]] + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)]) + C = [[1, 2, 3]] + cls.gc.append((G, C)) + + # Eppstein's tests + G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []}) + C = [[0], [1], [2], [3], [4], [5], [6]] + cls.gc.append((G, C)) + + G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]}) + C = [[0, 1, 2], [3, 4]] + cls.gc.append((G, C)) + + G = nx.DiGraph() + C = [] + cls.gc.append((G, C)) + + def test_connected_components(self): + # Test duplicated below + cc = nx.connected_components + G = self.G + C = { + frozenset([0, 1, 2, 3]), + frozenset([4, 5, 6, 7, 8, 9]), + frozenset([10, 11, 12, 13, 14]), + } + assert {frozenset(g) for g in cc(G)} == C + + def test_connected_components_nx_loopback(self): + # This tests the @nx._dispatchable mechanism, treating nx.connected_components + # as if it were a re-implementation from another package. + # Test duplicated from above + cc = nx.connected_components + G = dispatch_interface.convert(self.G) + C = { + frozenset([0, 1, 2, 3]), + frozenset([4, 5, 6, 7, 8, 9]), + frozenset([10, 11, 12, 13, 14]), + } + if "nx_loopback" in nx.config.backends or not nx.config.backends: + # If `nx.config.backends` is empty, then `_dispatchable.__call__` takes a + # "fast path" and does not check graph inputs, so using an unknown backend + # here will still work. + assert {frozenset(g) for g in cc(G)} == C + else: + # This raises, because "nx_loopback" is not registered as a backend. + with pytest.raises( + ImportError, match="'nx_loopback' backend is not installed" + ): + cc(G) + + def test_number_connected_components(self): + ncc = nx.number_connected_components + assert ncc(self.G) == 3 + + def test_number_connected_components2(self): + ncc = nx.number_connected_components + assert ncc(self.grid) == 1 + + def test_connected_components2(self): + cc = nx.connected_components + G = self.grid + C = {frozenset([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16])} + assert {frozenset(g) for g in cc(G)} == C + + def test_node_connected_components(self): + ncc = nx.node_connected_component + G = self.grid + C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16} + assert ncc(G, 1) == C + + def test_is_connected(self): + assert nx.is_connected(self.grid) + G = nx.Graph() + G.add_nodes_from([1, 2]) + assert not nx.is_connected(G) + + def test_connected_raise(self): + with pytest.raises(NetworkXNotImplemented): + next(nx.connected_components(self.DG)) + pytest.raises(NetworkXNotImplemented, nx.number_connected_components, self.DG) + pytest.raises(NetworkXNotImplemented, nx.node_connected_component, self.DG, 1) + pytest.raises(NetworkXNotImplemented, nx.is_connected, self.DG) + pytest.raises(nx.NetworkXPointlessConcept, nx.is_connected, nx.Graph()) + + def test_connected_mutability(self): + G = self.grid + seen = set() + for component in nx.connected_components(G): + assert len(seen & component) == 0 + seen.update(component) + component.clear() diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_semiconnected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_semiconnected.py new file mode 100644 index 00000000..6376bbfb --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_semiconnected.py @@ -0,0 +1,55 @@ +from itertools import chain + +import pytest + +import networkx as nx + + +class TestIsSemiconnected: + def test_undirected(self): + pytest.raises(nx.NetworkXNotImplemented, nx.is_semiconnected, nx.Graph()) + pytest.raises(nx.NetworkXNotImplemented, nx.is_semiconnected, nx.MultiGraph()) + + def test_empty(self): + pytest.raises(nx.NetworkXPointlessConcept, nx.is_semiconnected, nx.DiGraph()) + pytest.raises( + nx.NetworkXPointlessConcept, nx.is_semiconnected, nx.MultiDiGraph() + ) + + def test_single_node_graph(self): + G = nx.DiGraph() + G.add_node(0) + assert nx.is_semiconnected(G) + + def test_path(self): + G = nx.path_graph(100, create_using=nx.DiGraph()) + assert nx.is_semiconnected(G) + G.add_edge(100, 99) + assert not nx.is_semiconnected(G) + + def test_cycle(self): + G = nx.cycle_graph(100, create_using=nx.DiGraph()) + assert nx.is_semiconnected(G) + G = nx.path_graph(100, create_using=nx.DiGraph()) + G.add_edge(0, 99) + assert nx.is_semiconnected(G) + + def test_tree(self): + G = nx.DiGraph() + G.add_edges_from( + chain.from_iterable([(i, 2 * i + 1), (i, 2 * i + 2)] for i in range(100)) + ) + assert not nx.is_semiconnected(G) + + def test_dumbbell(self): + G = nx.cycle_graph(100, create_using=nx.DiGraph()) + G.add_edges_from((i + 100, (i + 1) % 100 + 100) for i in range(100)) + assert not nx.is_semiconnected(G) # G is disconnected. + G.add_edge(100, 99) + assert nx.is_semiconnected(G) + + def test_alternating_path(self): + G = nx.DiGraph( + chain.from_iterable([(i, i - 1), (i, i + 1)] for i in range(0, 100, 2)) + ) + assert not nx.is_semiconnected(G) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_strongly_connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_strongly_connected.py new file mode 100644 index 00000000..27f40988 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_strongly_connected.py @@ -0,0 +1,193 @@ +import pytest + +import networkx as nx +from networkx import NetworkXNotImplemented + + +class TestStronglyConnected: + @classmethod + def setup_class(cls): + cls.gc = [] + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2), + (2, 3), + (2, 8), + (3, 4), + (3, 7), + (4, 5), + (5, 3), + (5, 6), + (7, 4), + (7, 6), + (8, 1), + (8, 7), + ] + ) + C = {frozenset([3, 4, 5, 7]), frozenset([1, 2, 8]), frozenset([6])} + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)]) + C = {frozenset([2, 3, 4]), frozenset([1])} + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)]) + C = {frozenset([1, 2, 3])} + cls.gc.append((G, C)) + + # Eppstein's tests + G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []}) + C = { + frozenset([0]), + frozenset([1]), + frozenset([2]), + frozenset([3]), + frozenset([4]), + frozenset([5]), + frozenset([6]), + } + cls.gc.append((G, C)) + + G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]}) + C = {frozenset([0, 1, 2]), frozenset([3, 4])} + cls.gc.append((G, C)) + + def test_tarjan(self): + scc = nx.strongly_connected_components + for G, C in self.gc: + assert {frozenset(g) for g in scc(G)} == C + + def test_kosaraju(self): + scc = nx.kosaraju_strongly_connected_components + for G, C in self.gc: + assert {frozenset(g) for g in scc(G)} == C + + def test_number_strongly_connected_components(self): + ncc = nx.number_strongly_connected_components + for G, C in self.gc: + assert ncc(G) == len(C) + + def test_is_strongly_connected(self): + for G, C in self.gc: + if len(C) == 1: + assert nx.is_strongly_connected(G) + else: + assert not nx.is_strongly_connected(G) + + def test_contract_scc1(self): + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2), + (2, 3), + (2, 11), + (2, 12), + (3, 4), + (4, 3), + (4, 5), + (5, 6), + (6, 5), + (6, 7), + (7, 8), + (7, 9), + (7, 10), + (8, 9), + (9, 7), + (10, 6), + (11, 2), + (11, 4), + (11, 6), + (12, 6), + (12, 11), + ] + ) + scc = list(nx.strongly_connected_components(G)) + cG = nx.condensation(G, scc) + # DAG + assert nx.is_directed_acyclic_graph(cG) + # nodes + assert sorted(cG.nodes()) == [0, 1, 2, 3] + # edges + mapping = {} + for i, component in enumerate(scc): + for n in component: + mapping[n] = i + edge = (mapping[2], mapping[3]) + assert cG.has_edge(*edge) + edge = (mapping[2], mapping[5]) + assert cG.has_edge(*edge) + edge = (mapping[3], mapping[5]) + assert cG.has_edge(*edge) + + def test_contract_scc_isolate(self): + # Bug found and fixed in [1687]. + G = nx.DiGraph() + G.add_edge(1, 2) + G.add_edge(2, 1) + scc = list(nx.strongly_connected_components(G)) + cG = nx.condensation(G, scc) + assert list(cG.nodes()) == [0] + assert list(cG.edges()) == [] + + def test_contract_scc_edge(self): + G = nx.DiGraph() + G.add_edge(1, 2) + G.add_edge(2, 1) + G.add_edge(2, 3) + G.add_edge(3, 4) + G.add_edge(4, 3) + scc = list(nx.strongly_connected_components(G)) + cG = nx.condensation(G, scc) + assert sorted(cG.nodes()) == [0, 1] + if 1 in scc[0]: + edge = (0, 1) + else: + edge = (1, 0) + assert list(cG.edges()) == [edge] + + def test_condensation_mapping_and_members(self): + G, C = self.gc[1] + C = sorted(C, key=len, reverse=True) + cG = nx.condensation(G) + mapping = cG.graph["mapping"] + assert all(n in G for n in mapping) + assert all(0 == cN for n, cN in mapping.items() if n in C[0]) + assert all(1 == cN for n, cN in mapping.items() if n in C[1]) + for n, d in cG.nodes(data=True): + assert set(C[n]) == cG.nodes[n]["members"] + + def test_null_graph(self): + G = nx.DiGraph() + assert list(nx.strongly_connected_components(G)) == [] + assert list(nx.kosaraju_strongly_connected_components(G)) == [] + assert len(nx.condensation(G)) == 0 + pytest.raises( + nx.NetworkXPointlessConcept, nx.is_strongly_connected, nx.DiGraph() + ) + + def test_connected_raise(self): + G = nx.Graph() + with pytest.raises(NetworkXNotImplemented): + next(nx.strongly_connected_components(G)) + with pytest.raises(NetworkXNotImplemented): + next(nx.kosaraju_strongly_connected_components(G)) + pytest.raises(NetworkXNotImplemented, nx.is_strongly_connected, G) + pytest.raises(NetworkXNotImplemented, nx.condensation, G) + + strong_cc_methods = ( + nx.strongly_connected_components, + nx.kosaraju_strongly_connected_components, + ) + + @pytest.mark.parametrize("get_components", strong_cc_methods) + def test_connected_mutability(self, get_components): + DG = nx.path_graph(5, create_using=nx.DiGraph) + G = nx.disjoint_union(DG, DG) + seen = set() + for component in get_components(G): + assert len(seen & component) == 0 + seen.update(component) + component.clear() diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_weakly_connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_weakly_connected.py new file mode 100644 index 00000000..f0144789 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/tests/test_weakly_connected.py @@ -0,0 +1,96 @@ +import pytest + +import networkx as nx +from networkx import NetworkXNotImplemented + + +class TestWeaklyConnected: + @classmethod + def setup_class(cls): + cls.gc = [] + G = nx.DiGraph() + G.add_edges_from( + [ + (1, 2), + (2, 3), + (2, 8), + (3, 4), + (3, 7), + (4, 5), + (5, 3), + (5, 6), + (7, 4), + (7, 6), + (8, 1), + (8, 7), + ] + ) + C = [[3, 4, 5, 7], [1, 2, 8], [6]] + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)]) + C = [[2, 3, 4], [1]] + cls.gc.append((G, C)) + + G = nx.DiGraph() + G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)]) + C = [[1, 2, 3]] + cls.gc.append((G, C)) + + # Eppstein's tests + G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []}) + C = [[0], [1], [2], [3], [4], [5], [6]] + cls.gc.append((G, C)) + + G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]}) + C = [[0, 1, 2], [3, 4]] + cls.gc.append((G, C)) + + def test_weakly_connected_components(self): + for G, C in self.gc: + U = G.to_undirected() + w = {frozenset(g) for g in nx.weakly_connected_components(G)} + c = {frozenset(g) for g in nx.connected_components(U)} + assert w == c + + def test_number_weakly_connected_components(self): + for G, C in self.gc: + U = G.to_undirected() + w = nx.number_weakly_connected_components(G) + c = nx.number_connected_components(U) + assert w == c + + def test_is_weakly_connected(self): + for G, C in self.gc: + U = G.to_undirected() + assert nx.is_weakly_connected(G) == nx.is_connected(U) + + def test_null_graph(self): + G = nx.DiGraph() + assert list(nx.weakly_connected_components(G)) == [] + assert nx.number_weakly_connected_components(G) == 0 + with pytest.raises(nx.NetworkXPointlessConcept): + next(nx.is_weakly_connected(G)) + + def test_connected_raise(self): + G = nx.Graph() + with pytest.raises(NetworkXNotImplemented): + next(nx.weakly_connected_components(G)) + pytest.raises(NetworkXNotImplemented, nx.number_weakly_connected_components, G) + pytest.raises(NetworkXNotImplemented, nx.is_weakly_connected, G) + + def test_connected_mutability(self): + DG = nx.path_graph(5, create_using=nx.DiGraph) + G = nx.disjoint_union(DG, DG) + seen = set() + for component in nx.weakly_connected_components(G): + assert len(seen & component) == 0 + seen.update(component) + component.clear() + + +def test_is_weakly_connected_empty_graph_raises(): + G = nx.DiGraph() + with pytest.raises(nx.NetworkXPointlessConcept, match="Connectivity is undefined"): + nx.is_weakly_connected(G) diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/weakly_connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/weakly_connected.py new file mode 100644 index 00000000..ecfac50a --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/weakly_connected.py @@ -0,0 +1,197 @@ +"""Weakly connected components.""" + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +__all__ = [ + "number_weakly_connected_components", + "weakly_connected_components", + "is_weakly_connected", +] + + +@not_implemented_for("undirected") +@nx._dispatchable +def weakly_connected_components(G): + """Generate weakly connected components of G. + + Parameters + ---------- + G : NetworkX graph + A directed graph + + Returns + ------- + comp : generator of sets + A generator of sets of nodes, one for each weakly connected + component of G. + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + Generate a sorted list of weakly connected components, largest first. + + >>> G = nx.path_graph(4, create_using=nx.DiGraph()) + >>> nx.add_path(G, [10, 11, 12]) + >>> [ + ... len(c) + ... for c in sorted(nx.weakly_connected_components(G), key=len, reverse=True) + ... ] + [4, 3] + + If you only want the largest component, it's more efficient to + use max instead of sort: + + >>> largest_cc = max(nx.weakly_connected_components(G), key=len) + + See Also + -------- + connected_components + strongly_connected_components + + Notes + ----- + For directed graphs only. + + """ + seen = set() + n = len(G) # must be outside the loop to avoid performance hit with graph views + for v in G: + if v not in seen: + c = set(_plain_bfs(G, n, v)) + seen.update(c) + yield c + + +@not_implemented_for("undirected") +@nx._dispatchable +def number_weakly_connected_components(G): + """Returns the number of weakly connected components in G. + + Parameters + ---------- + G : NetworkX graph + A directed graph. + + Returns + ------- + n : integer + Number of weakly connected components + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + >>> G = nx.DiGraph([(0, 1), (2, 1), (3, 4)]) + >>> nx.number_weakly_connected_components(G) + 2 + + See Also + -------- + weakly_connected_components + number_connected_components + number_strongly_connected_components + + Notes + ----- + For directed graphs only. + + """ + return sum(1 for wcc in weakly_connected_components(G)) + + +@not_implemented_for("undirected") +@nx._dispatchable +def is_weakly_connected(G): + """Test directed graph for weak connectivity. + + A directed graph is weakly connected if and only if the graph + is connected when the direction of the edge between nodes is ignored. + + Note that if a graph is strongly connected (i.e. the graph is connected + even when we account for directionality), it is by definition weakly + connected as well. + + Parameters + ---------- + G : NetworkX Graph + A directed graph. + + Returns + ------- + connected : bool + True if the graph is weakly connected, False otherwise. + + Raises + ------ + NetworkXNotImplemented + If G is undirected. + + Examples + -------- + >>> G = nx.DiGraph([(0, 1), (2, 1)]) + >>> G.add_node(3) + >>> nx.is_weakly_connected(G) # node 3 is not connected to the graph + False + >>> G.add_edge(2, 3) + >>> nx.is_weakly_connected(G) + True + + See Also + -------- + is_strongly_connected + is_semiconnected + is_connected + is_biconnected + weakly_connected_components + + Notes + ----- + For directed graphs only. + + """ + if len(G) == 0: + raise nx.NetworkXPointlessConcept( + """Connectivity is undefined for the null graph.""" + ) + + return len(next(weakly_connected_components(G))) == len(G) + + +def _plain_bfs(G, n, source): + """A fast BFS node generator + + The direction of the edge between nodes is ignored. + + For directed graphs only. + + """ + Gsucc = G._succ + Gpred = G._pred + seen = {source} + nextlevel = [source] + + yield source + while nextlevel: + thislevel = nextlevel + nextlevel = [] + for v in thislevel: + for w in Gsucc[v]: + if w not in seen: + seen.add(w) + nextlevel.append(w) + yield w + for w in Gpred[v]: + if w not in seen: + seen.add(w) + nextlevel.append(w) + yield w + if len(seen) == n: + return |