Avoid pointless discards during the reuse and target phases
#3862
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Zac-HD
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Nice! Probably closes #3446, too. |
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This problem was jointly identified in discussion of #3827 with @tybug and @hgoldstein95. Finding this kind of performance issue without knowing to look for it is a great illustration of the value of observability!
It turns out that we're spuriously aborting many test cases with status=Overrun, due to
ConjectureData.from_buffer()limiting the max length to the length of the provided bytestring unlessextend=...is passed. This makes sense in theshrinkphase - any longer buffer cannot be a successful shrink, so we may as well abort early - but not in thereuseortargetphases.reusephase is easy to fix: simply add the relevant argument to allow extending buffers replayed from the database - we'll get different behaviour, but get a performance gain (and maybe avoidHealthCheck.filter_too_much) by finishing this test case rather than retrying in thegeneratephase.targetphase is a little more complicated, and ... it turns out that by the time I worked out how we'd need to thread state through to the shrinker I had 80% of a fix, so this is now a PR rather than an issue 馃槄Tests tbd when I have some more time.