[issue26163] FAIL: test_hash_effectiveness (test.test_set.TestFrozenSet)
Tim Peters
report at bugs.python.org
Thu Oct 20 21:50:22 EDT 2016
Tim Peters added the comment:
I think Raymond will have to chime in. I assume this is due to the `letter_range` portion of the test suffering hash randomization dealing it a bad hand - but the underlying string hash is "supposed to be" strong regardless of seed. The
self.assertGreater(4*u, t)
AssertionError: 124 not greater than 128
failure says 128 distinct sets hashed to only u = 124/4 = 31 distinct values across their hashes' last 7 bits, and that's worth complaining about. It's way too many collisions.
It _may_ be a flaw in the set hash, or in the string hash, or just plain bad luck, but there's really no way to know which without digging into details.
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nosy: +tim.peters
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