Use numpy sum instead of comprehension in _score_heuristic #5403
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In sabre_swap the comprehension in _score_heuristic() with the basic heuristic starts to become a bottleneck as the size of the coupling map increases. This probably becomes the top bottleneck in a transpilation after Qiskit#5316, Qiskit#5183, Qiskit#5294, Qiskit#5267, and Qiskit#5272 are merged. This commit is an attempt to try and mitigate that a bit by using numpy native operations instead of a python comprehension in sum(). If this is insufficient we'll likely have to either avoid doing a sum like this or drop down to a lower level with cython or rust and operate on the array directly to remove this bottleneck.
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Still need to benchmark this to see if it actually makes a difference or not. Since to really see the bottleneck we need a bunch of PRs at once I'll have to setup an environment to benchmark this reliably. |
itoko
reviewed
Nov 18, 2020
Comment on lines
318
to
320
| if self.coupling_map._dist_matrix is None: | ||
| self.coupling_map._compute_distance_matrix() | ||
| return self.coupling_map._dist_matrix[ |
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It might be better to put these lines to dist_matrix property in CouplingMap class (if we don't mind one function call).
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Yeah, that's a good idea. I made this change in: 8df570f
ajavadia
approved these changes
Nov 24, 2020
Merged
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Summary
In sabre_swap the comprehension in _score_heuristic() with the basic
heuristic starts to become a bottleneck as the size of the coupling map
increases. This probably becomes the top bottleneck in a transpilation
with sabre after #5316, #5183, #5294, #5267, and #5272 are merged. This commit is
an attempt to try and mitigate that a bit by using numpy native
operations instead of a python comprehension in sum(). If this is
insufficient we'll likely have to either avoid doing a sum like this or
drop down to a lower level with cython or rust and operate on the array
directly to remove this bottleneck.
Details and comments