Optimization: Avoid quadratic behavior in IdMaker.make_unique_parameterset_ids#14739
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Optimization: Avoid quadratic behavior in IdMaker.make_unique_parameterset_ids#14739NoxiousTab wants to merge 2 commits into
NoxiousTab wants to merge 2 commits into
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make_unique_parameterset_ids rebuilt set(resolved_ids) from scratch on every candidate suffix it tried while de-duplicating parametrize ids. For parametrizations with many colliding ids this made the method scale O(n^2) with the number of parameter sets. Build the set of in-use ids once and keep it updated incrementally instead, bringing this down to linear time. Confirmed with a manual benchmark, runtime dropped from ~0.64s to ~0.01s, and the doubling ratio changed from ~4x (quadratic) to ~2x (linear).
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The Problem
IdMaker.make_unique_parameterset_ids(used to generate node ids for@pytest.mark.parametrize) rebuiltset(resolved_ids)from scratch onevery candidate suffix it tried while de-duplicating colliding ids.
That set-rebuild is O(n), and it sat inside a loop over every parameter
set, making the whole de-duplication step O(n**2) in the number of
parameter sets whenever many of them produce the same id (e.g.
parametrizing with many values that stringify identically, or with
duplicate user-provided ids).
Fix
Build the set of in-use ids once, and update it incrementally as new
ids are assigned, instead of rebuilding it from the list on every
check. This brings the de-duplication step down to O(n).
Testing
make_unique_parameterset_ids()directly with N colliding ids:runtime scaling went from ~4x per doubling of N (quadratic) to ~2x
per doubling (linear), roughly 55x faster at N=8000.
testing/python/metafunc.py::TestMetafunc::test_idmaker_*tests pass unchanged.
testing/python/suite passes (629 passed, 24 skipped, 2 xfailed— the xfails are pre-existing and unrelated to this change).