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test_hash(): The test here is different enough from the one in the bug

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report that the stats for expected # of collisions are a little higher.
Updated comments accordingly.
This commit is contained in:
Tim Peters 2004-06-01 18:58:04 +00:00
parent 7897ff0d9a
commit 1f4bcf9edd
1 changed files with 7 additions and 3 deletions
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10
Lib/test/test_tuple.py
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@ -49,9 +49,13 @@ def test_hash(self):
# should not exhibit cancellation in tuples like (x,(x,y))
# should be distinct from element hashes: hash(x)!=hash((x,))
# This test exercises those cases.
# For a pure random hash and N=50, the expected number of collisions
# is 7.3. Here we allow twice that number.
# Any worse and the hash function is sorely suspect.
# For a pure random hash and N=50, the expected number of occupied
# buckets when tossing 252,600 balls into 2**32 buckets
# is 252,592.6, or about 7.4 expected collisions. The
# standard deviation is 2.73. On a box with 64-bit hash
# codes, no collisions are expected. Here we accept no
# more than 15 collisions. Any worse and the hash function
# is sorely suspect.
N=50
base = range(N)