faster state_number_enumerate #1594
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When the number of excitations is limited, instead of iterating over all states and discarding the ones with too many excitations, directly choose the limits to only iterate over allowed states. As a small additional optimization, do not redo the same sum every time, but keep track of the sum within the algorithm.
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This and #1593 both look like solid improvements to me, I did a little testing and couldn't break anything. Also your approach makes the code much more readable than it was. Probably @hodgestar can comment on whether it is best to combine them into one? |
Ericgig
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Jul 6, 2021
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I've given it a shot in #1604, together with some other (possible) improvements. |
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Faster state_number_enumerate implementation.
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Description
When the number of excitations in
state_number_enumerateis limited, instead of iterating over all states and discarding the ones with too many excitations, directly choose the limits to only iterate over allowed states. As a small additional optimization, do not redo the same sum every time, but keep track of the sum within the algorithm. For the tests I've made, this is a factor of ~4-10 faster than the current version. Together with #1593, this reduces the runtime ofenr_destroy(which usesstate_number_enumerate) from almost 4s to 15 ms for the case I just treated, and another much bigger case takes 2.5 s now, while it hadn't finished after more than an hour with the previous version.Note that since the two PRs (this one and #1593) are somewhat related, it might make sense to combine them into a single one. I'd be happy to do that.
Changelog
Made state_number_enumerate somewhat faster.