Optimize UnrollCustomDefinitions pass #10777
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This commit makes some small tweaks to the UnrollCustomDefinitions pass to optimize it's runtime performance. It makes 2 primary changes to improve the efficiency. First, when calling `circuit_to_dag()` the copy_operations flag is set to False. This eliminates an inner deep copy from the conversion which will make the conversion operate more efficiently. The second is previously on every recursive call to run the pass we were previously reconstructing the pass on every execution. Instead this just reuses the existing instance. This will have less measurable of an impact as the pass construction is relatively fast, but it was unecessary work as we already have a pass object that can reused.
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jakelishman
approved these changes
Sep 5, 2023
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This seems correct - a transpiler pass is allowed to consider itself as owning the circuit that comes into it, so the copy=False is sound. Reusing self also just seems better in principle if nothing else - were we to be doing any per-run caching here, there's no reason not to share it between scopes.
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Summary
This commit makes some small tweaks to the UnrollCustomDefinitions pass to optimize it's runtime performance. It makes 2 primary changes to improve the efficiency. First, when calling
circuit_to_dag()the copy_operations flag is set to False. This eliminates an inner deep copy from the conversion which will make the conversion operate more efficiently. The second is previously on every recursive call to run the pass we were previously reconstructing the pass on every execution. Instead this just reuses the existing instance. This will have less measurable of an impact as the pass construction is relatively fast, but it was unecessary work as we already have a pass object that can reused.Details and comments