Avoid inner-loop allocations in longest_path#1577
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jakelishman wants to merge 1 commit intoQiskit:mainfrom
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Avoid inner-loop allocations in longest_path#1577jakelishman wants to merge 1 commit intoQiskit:mainfrom
longest_path#1577jakelishman wants to merge 1 commit intoQiskit:mainfrom
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The only use of the per-node `Vec` is to consume it immediately into a `max_by` iterator. Rewriting the allocating loop as a single `try_fold` removes the unnecessary allocation. On a test 1.6 million gate circuit over on Qiskit, this sped up our use of `longest_path` from 150ms to 100ms, and there's further follow-on improvements available by changing the interfaces to allow path-length calculation without constructing the path itself.
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The only use of the per-node
Vecis to consume it immediately into amax_byiterator. Rewriting the allocating loop as a singletry_foldremoves the unnecessary allocation.On a test 1.6 million gate circuit over on Qiskit, this sped up our use of
longest_pathfrom 150ms to 50ms, so a 3x improvement.