Improve OpenQASM 3 exporter performance for hardware-like circuits #13343
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This reorganises the variable lookups and internal AST generation slightly to improve the OpenQASM 3 exporter performance for the common case of circuits with many singly parametric 1q gates, parametrised by a single `Parameter` expression. This is quite common in high-throughput cases, where the circuit is being used as a parametric template for a backend compiler.
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| @@ -1145,9 +1145,11 @@ def _rebind_scoped_parameters(self, expression): | |||
| # missing, pending a new system in Terra to replace it (2022-03-07). | |||
| if not isinstance(expression, ParameterExpression): | |||
| return expression | |||
| if isinstance(expression, Parameter): | |||
| return self.symbols.get_variable(expression).string | |||
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Is this a different behavior here? I've not looked too much at ParameterExpression, but is it odd for this to return a string rather than an Expression? Perhaps I'm missing something 🙂
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You're not missing anything, it's just abuse of the complete absence of handling for ParameterExpression in the exporter - we literally just call str and hope for the best.
The reason not to construct a ParameterExpression is because the case of a standalone Parameter is very common on the performance critical path, and ParameterExpression (and Parameter) are both very expensive to construct.
kevinhartman
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Nov 1, 2024
joshuasn
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Dec 18, 2024
…cuits (Qiskit#13343)" This reverts commit 8b21013.
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Summary
This reorganises the variable lookups and internal AST generation slightly to improve the OpenQASM 3 exporter performance for the common case of circuits with many singly parametric 1q gates, parametrised by a single
Parameterexpression. This is quite common in high-throughput cases, where the circuit is being used as a parametric template for a backend compiler.Details and comments
Similar to #13342, this was a couple of very easy tweaks I could make within Python space to slightly improve the runtime performance of the OQ3 importer. It's still pretty slow for what it does, but there's little point focussing on its performance while it's still pure Python, and the majority of our data models are moving to Rust.