Add longest_path_length to rustworkx_core::dag_algo#1605
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IvanIsCoding merged 3 commits intoJun 18, 2026
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This commit builds off of Qiskit#1577 which improved the performance of the `longest_path` function to avoid allocating on each iteration of the loop. It was pointed out in that PR and Qiskit#1563 that storing and returning a path for applications that only care about the length is unnecessary overhead. To provide an option for such cases a new function is added to offer a better alternative for these use cases.
Since path weights might be floating point numbers or other types which don't implment Ord we need to handle the case where the comparison isn't possible (e.g. for floats the presence of NaN). Previously we just were treating this as equal which is not correct. This commit updates the logic in the path length function to just return None in the presence of non comparable elements along the longest path and adds documentation to tell users about this and suggestions on how to handle this case in the weight functions.
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I forgot to put in the commit message, but the reason for the seeming duplication here is that internally I changed the typing of the |
IvanIsCoding
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LGTM. The tests are good, existing test pass. It should be an easy merge. It is bound to be faster than the code we had before.
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This commit builds off of #1577 which improved the performance of the
longest_pathfunction to avoid allocating on each iteration of the loop. It was pointed out in that PR and #1563 that storing and returning a path for applications that only care about the length is unnecessary overhead. To provide an option for such cases a new function is added to offer a better alternative for these use cases.