Investigate test_set.TestFrozenSet.test_hash_effectiveness performance

[dchiquito]

Summary

test_set.TestFrozenSet.test_hash_effectiveness verifies some properties of frozenset.__hash__. One of the steps involves calculating the hash of powerset(range(18)). This part of the test runs so slowly that the parameters had to be reduced for it to finish.

Expected

The test runs as written in an acceptable time frame.

Actual

The test has been modified to powerset(range(13)).

Code in question

        def powerset(s):
            for i in range(len(s)+1):
                yield from map(frozenset, itertools.combinations(s, i))

        for n in range(18):
            t = 2 ** n
            mask = t - 1
            for nums in (range, zf_range):
                u = len({h & mask for h in map(hash, powerset(nums(n)))})
                self.assertGreater(4*u, t)

I suspect the problem is in generating the powerset, not calculating the hash.