Improvement in performance of resolve_parameters

[skushnir123]

This PR is in response to #6091 where it was brought up that cirq.resolve_parameters is very slow. This one-line PR speeds up the performance of the problem mentioned in the issue by a factor of ~6x (at least on my computer) and is comparable with qiskit's bind_parameters. The issue I found was that Sympy's subs function was being run on Floats which didn't do anything but took up the majority of the running time.

Before my change:

Elapsed cirq.resolve_parameters: 0.00469
Elapsed construct from scratch: 0.00033

After my change:

Elapsed cirq.resolve_parameters: 0.00079
Elapsed construct from scratch: 0.00027

Note: difference of ~6x

[tanujkhattar]

Can you post results from running the before/after benchmarks from the original issue and also from https://github.com/quantumlib/Cirq/blob/master/benchmarks/parameter_resolution.py ?

[tanujkhattar]

Can you also run the asv benchmark https://github.com/quantumlib/Cirq/blob/master/benchmarks/parameter_resolution.py ?

[skushnir123]

Can you also run the asv benchmark https://github.com/quantumlib/Cirq/blob/master/benchmarks/parameter_resolution.py ?

Yes, I will. I'm a bit busy today and tomorrow but will do on sunday.

[tanujkhattar]

@skushnir123 We can keep the PR open?

[tanujkhattar]

I ran the benchmarks and it mostly looks good. I also think the parameter resolution benchmark should be probably be rewritten because there's a lot of time that goes in Circuit construction. Either way, this PR is good to merge. Thanks for the fix @skushnir123 !

       before           after         ratio
     [24abfa1d]       [abf0f389]
     <master>         <slow-resolve_parameters>
-        129±10ms          112±4ms     0.87  parameter_resolution.RabiCalibration.time_parameter_resolution(200, 20) [tanujkhattar-macbookpro2.roam.corp.google.com/virtualenv-py3.10-PYTHONOPTIMIZE-O]
-        508±30ms         440±20ms     0.87  parameter_resolution.RabiCalibration.time_parameter_resolution(150, 100) [tanujkhattar-macbookpro2.roam.corp.google.com/virtualenv-py3.10-PYTHONOPTIMIZE-O]
-        551±60ms         422±10ms     0.77  parameter_resolution.RabiCalibration.time_parameter_resolution(200, 80) [tanujkhattar-macbookpro2.roam.corp.google.com/virtualenv-py3.10-PYTHONOPTIMIZE-O]
-       504±100ms         312±20ms     0.62  parameter_resolution.RabiCalibration.time_parameter_resolution(200, 60) [tanujkhattar-macbookpro2.roam.corp.google.com/virtualenv-py3.10-PYTHONOPTIMIZE-O]