PNC k shortest simple path (for directed graphs) #40284
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…o this implementation)
src/sage/graphs/path_enumeration.pyx
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| G.delete_edges(G.incoming_edges(source, labels=False)) | ||
| G.delete_edges(G.outgoing_edges(target, labels=False)) | ||
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| if weight_function is not None: |
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this is done by the call to _get_weight_function. No need to duplicate.
src/sage/graphs/path_enumeration.pyx
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| if self.has_loops() or self.allows_multiple_edges(): | ||
| G = self.to_simple(to_undirected=False, keep_label='min', immutable=False) | ||
| else: | ||
| G = self.copy() |
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to be on the safe side, use self.copy(immutable=False)
src/sage/graphs/path_enumeration.pyx
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| reverse_graph = G.reverse() | ||
| dist, successor = shortest_paths(reverse_graph, target, weight_function=reverse_weight_function, | ||
| algorithm='Dijkstra_Boost') | ||
| cdef set unnecessary_vertices = set(G) - set(dist) # no path to target |
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always add 2 spaces before a comment at the end of a line, so set(list) # vertices with no path to target
src/sage/graphs/path_enumeration.pyx
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| # ancestor_idx_dict[v] := the first vertex reachable by edges of | ||
| # first shortest path tree from v | ||
| ancestor_idx_dict = dict() |
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ancestor_idx_dict = {v: i for I, v in enumerate(path)}
Because I want to use priority_queue of C++ standard library, the type of PathCandidate must be struct of C++. Thus, I think I need definition of PathCandidate in .h file. However, There may be another way of doing so without .h file. I am looking for it. |
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isn't it possible to use a tuple instead of PathCandidate ? or may be |
src/sage/graphs/path_enumeration.pyx
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| @@ -36,6 +36,7 @@ from sage.misc.misc_c import prod | |||
| from libcpp.queue cimport priority_queue | |||
| from libcpp.pair cimport pair | |||
| from sage.rings.integer_ring import ZZ | |||
| from sage.graphs.path_enumeration cimport PathCandidate | |||
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remove this line. Otherwise it fails to compile.
| sage: list(pnc_k_shortest_simple_paths(g, 1, 5, by_weight=True)) | ||
| [[1, 3, 5], [1, 2, 5], [1, 4, 5]] | ||
| TESTS: |
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add another test to compare the results with Yen, at least the sequence of weights. Paths with the same weight may be reported in different orders.
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something goes wrong in the algorithm. Paths are not reported in increasing order of weight sage: g = DiGraph(graphs.Grid2dGraph(2, 6).relabel(inplace=False))
sage: for u, v in g.edge_iterator(labels=False):
....: g.set_edge_label(u, v, 1)
sage: %time X = [w for w, P in pnc_k_shortest_simple_paths(g, 5, 1, by_weight=True, report_weight=True, labels=True, report_edges=True)]
CPU times: user 1.39 ms, sys: 0 ns, total: 1.39 ms
Wall time: 1.4 ms
sage: print(X)
[4.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 10.0, 10.0, 10.0, 10.0, 8.0] |
src/sage/graphs/path_enumeration.pyx
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| [4.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 6.0, 8.0, 8.0, | ||
| 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 8.0, 10.0, 10.0, 10.0, 10.0] | ||
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| Same tests as yen_k_shortest_simple_paths:: |
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You should rebase the branch on the last beta. If you do another commit, you can add the doi to the paper |
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It's not fully fixed sage: from sage.graphs.path_enumeration import yen_k_shortest_simple_paths as yen
sage: from sage.graphs.path_enumeration import feng_k_shortest_simple_paths as feng
sage: from sage.graphs.path_enumeration import pnc_k_shortest_simple_paths as pnc
sage: D = graphs.Grid2dGraph(5, 5).relabel(inplace=False).to_directed()
sage: %time len(list(yen(D, 0, 24)))
CPU times: user 14 s, sys: 408 µs, total: 14 s
Wall time: 14.1 s
8512
sage: %time len(list(feng(D, 0, 24)))
CPU times: user 1.23 s, sys: 988 µs, total: 1.23 s
Wall time: 1.24 s
8512
sage: %time len(list(pnc(D, 0, 24)))
CPU times: user 427 ms, sys: 995 µs, total: 428 ms
Wall time: 428 ms
8530 |
Implement PNC k shortest simple path for directed graphs.
I implemented for only directed graphs for simplicity first.
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⌛ Dependencies
#40248
#40217