Fix #1405: potential pool.join deadlock in ParallelLinearQubitOperator #1419
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mhucka merged 3 commits intoJul 16, 2026
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Consume imap_unordered results before joining the worker pool to avoid pipe backpressure deadlocks when state vectors are large.
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This pull request resolves a potential deadlock in ParallelLinearQubitOperator._matvec by consuming the results of the multiprocessing pool before calling pool.join(). It also adds a regression test, test_matvec_large_vector_multiprocess, to prevent future regressions. There are no review comments, so I have no feedback to provide.
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Jul 16, 2026
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Nice! Thanks for this. One minor suggestion.
Co-authored-by: Michael Hucka <mhucka@google.com>
Apply mhucka's pool.join() guard correctly: return stays after finally, not inside it.
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@mhucka applied suggestion but ci failed on black cause gh apply dropped the try/finally indentation and moved return result into the finally block. Pushed a fix that keeps your guard (pool.join() always runs) with correct indentation and return after the try/finally. Thanks for the hint <3 |
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Consume imap_unordered results before joining the worker pool to avoid pipe backpressure deadlocks when state vectors are large.
Fixes #1405