Fix preservation of order in align_right in cirq-core/cirq/transformers/align.py#6899
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dstrain115 merged 9 commits intoquantumlib:mainfrom Jan 15, 2025
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Order was not preserved for non-commutable measurements and controls in the same moment. Reversing the circuit's moments did not reverse the ops within those moments. The subsequent `align_left` could split those ops into separate moments. Then reversing the moments again would have the end result of reversing the order of those operations in the final circuit. This PR makes sure to reverse the order of ops within the moment prior to the call to `align_left`.
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #6899 +/- ##
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Coverage 97.87% 97.87%
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Files 1084 1084
Lines 94420 94465 +45
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+ Hits 92409 92455 +46
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Seems like test hit an unrelated glitch. Can someone rerun? cc @mhucka |
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@daxfohl Ack, sorry I didn't see this notification sooner. I just restarted the test run. |
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* Fix order preservation in align_right Order was not preserved for non-commutable measurements and controls in the same moment. Reversing the circuit's moments did not reverse the ops within those moments. The subsequent `align_left` could split those ops into separate moments. Then reversing the moments again would have the end result of reversing the order of those operations in the final circuit. This PR makes sure to reverse the order of ops within the moment prior to the call to `align_left`.
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align_rightwas implemented as e.g.reverse(align_left(reverse(circuit.moments))). However this did not guarantee order preservation for non-commuting operations in the same moment. Reversing the circuit's moments did not reverse the ops within those moments. The subsequentalign_leftcould split those ops into separate moments. Then reversing the moments again would have the end result of swapping the order of those operations in the final circuit.This PR ensures order is preserved, by making sure to reverse the order of ops within each moment prior to the call to
align_leftand re-reversing them prior to returning.Fixes #6727