Update NC k shortest simple path for Undirected graphs #40547
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
Documentation preview for this PR (built with commit 7fb197d; changes) is ready! 🎉 |
dcoudert
suggested changes
Aug 7, 2025
src/sage/graphs/path_enumeration.pyx
Outdated
| @@ -1163,9 +1174,11 @@ def nc_k_shortest_simple_paths(self, source, target, weight_function=None, | |||
| return | |||
|
|
|||
| if self.has_loops() or self.allows_multiple_edges(): | |||
| G = self.to_simple(to_undirected=False, keep_label='min', immutable=False) | |||
| G = self.to_simple(to_undirected=self.is_directed(), keep_label='min', immutable=False) | |||
There was a problem hiding this comment.
Here you force conversion to undirected graph. This seems wrong.
src/sage/graphs/path_enumeration.pyx
Outdated
| else: | ||
| G = self.copy(immutable=False) | ||
| if not G.is_directed(): |
There was a problem hiding this comment.
we can sometimes save a copy
if self.has_loops() or self.allows_multiple_edges():
G = self.to_simple(to_undirected=False, keep_label='min', immutable=False)
if not G.is_directed():
G = G.to_directed()
elif not self.is_directed():
# Turn the graph into a mutable directed graph
G = self.to_directed(data_structure='sparse')
else:
G = self.copy(immutable=False)
src/sage/graphs/path_enumeration.pyx
Outdated
| sage: list(nc_k_shortest_simple_paths(g, 5, 1, by_weight=True)) | ||
| [[5, 3, 1], [5, 2, 1], [5, 4, 1]] | ||
| sage: list(nc_k_shortest_simple_paths(g, 5, 1)) | ||
| [[5, 2, 1], [5, 4, 1], [5, 3, 1]] |
There was a problem hiding this comment.
The order in which the paths are reported may not always be the same. To make the test robust, you could report the length of the paths.
sage: [len(P) for P in nc_k_shortest_simple_paths(g, 5, 1)]
[3, 3, 3]the alternative is to use a lexicographic sorting of the paths
sage: sorted(nc_k_shortest_simple_paths(g, 5, 1))
[[5, 2, 1], [5, 3, 1], [5, 4, 1]]
src/sage/graphs/path_enumeration.pyx
Outdated
| Check that "Yen", "Feng" and "PNC" provide same results on random undirected graphs:: | ||
|
|
||
| sage: from sage.graphs.generators.random import RandomGNP | ||
| sage: G = RandomGNP(30, .05) |
There was a problem hiding this comment.
you could simply use G = graphs.RandomGNP(30, .05).
Also, consider increasing the number of edges. With p=0.05 the graph has roughly 20 edges.
vbraun
pushed a commit
to vbraun/sage
that referenced
this pull request
Aug 10, 2025
sagemathgh-40547: Update NC k shortest simple path for Undirected graphs <!-- ^ Please provide a concise and informative title. --> <!-- ^ Don't put issue numbers in the title, do this in the PR description below. --> <!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method to calculate 1 + 2". --> <!-- v Describe your changes below in detail. --> <!-- v Why is this change required? What problem does it solve? --> <!-- v If this PR resolves an open issue, please link to it here. For example, "Fixes sagemath#12345". --> Update nc_k_shortest_simple_path algorithm for undirected graphs. ### 📝 Checklist <!-- Put an `x` in all the boxes that apply. --> - [x] The title is concise and informative. - [x] The description explains in detail what this PR is about. - [x] I have linked a relevant issue or discussion. - [x] I have created tests covering the changes. - [ ] I have updated the documentation and checked the documentation preview. ### ⌛ Dependencies <!-- List all open PRs that this PR logically depends on. For example, --> <!-- - sagemath#12345: short description why this is a dependency --> <!-- - sagemath#34567: ... --> sagemath#40510 URL: sagemath#40547 Reported by: Yuta Inoue Reviewer(s): David Coudert
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Update nc_k_shortest_simple_path algorithm for undirected graphs.
📝 Checklist
⌛ Dependencies
#40510