quick performance measurements

Ben Gamari ben at smart-cactus.org
Fri Feb 12 20:48:31 UTC 2016

Richard Eisenberg <eir at cis.upenn.edu> writes:

> Hi devs,
> I have a few ideas for tweaks to improve compiler performance. (For
> example, reversing the order of comparisons in a short-circuiting
> comparison operation.) I don't have a particular test case with a
> profile that tells me where the smoking gun is. But I'd like to try
> these easy tweaks just to see if performance improves.
> My question: Is there an easy way to run some command that will give
> me helpful feedback on my performance tweak?
> Of course, I could push to a branch and have perf.haskell.org tell me.
> But that takes a long time. I could compile a few files and examine
> the output manually. But that's a bit painful. Ideally, there would be
> a way to run a portion of the testsuite and have the testsuite tool
> aggregate performance characteristics and report. Or perhaps there's a
> way to get cabal to aggregate performance characteristics, and I could
> just try compiling a few libraries. Any ideas out there?
Indeed I wish we had better infrastructure for this.

There is nofib, which IIRC tracks compile-time performance although the
coverage isn't terribly great. Otherwise, beyond tweaking the testsuite
driver as thomie suggests the options are sadly fairly limited.


- Ben
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