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1f4bcf9edd
report that the stats for expected # of collisions are a little higher. Updated comments accordingly.
72 lines
2.4 KiB
Python
72 lines
2.4 KiB
Python
import unittest
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from test import test_support, seq_tests
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class TupleTest(seq_tests.CommonTest):
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type2test = tuple
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def test_constructors(self):
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super(TupleTest, self).test_len()
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# calling built-in types without argument must return empty
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self.assertEqual(tuple(), ())
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def test_truth(self):
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super(TupleTest, self).test_truth()
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self.assert_(not ())
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self.assert_((42, ))
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def test_len(self):
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super(TupleTest, self).test_len()
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self.assertEqual(len(()), 0)
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self.assertEqual(len((0,)), 1)
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self.assertEqual(len((0, 1, 2)), 3)
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def test_iadd(self):
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super(TupleTest, self).test_iadd()
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u = (0, 1)
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u2 = u
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u += (2, 3)
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self.assert_(u is not u2)
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def test_imul(self):
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super(TupleTest, self).test_imul()
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u = (0, 1)
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u2 = u
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u *= 3
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self.assert_(u is not u2)
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def test_tupleresizebug(self):
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# Check that a specific bug in _PyTuple_Resize() is squashed.
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def f():
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for i in range(1000):
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yield i
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self.assertEqual(list(tuple(f())), range(1000))
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def test_hash(self):
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# See SF bug 942952: Weakness in tuple hash
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# The hash should:
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# be non-commutative
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# should spread-out closely spaced values
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# should not exhibit cancellation in tuples like (x,(x,y))
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# should be distinct from element hashes: hash(x)!=hash((x,))
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# This test exercises those cases.
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# For a pure random hash and N=50, the expected number of occupied
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# buckets when tossing 252,600 balls into 2**32 buckets
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# is 252,592.6, or about 7.4 expected collisions. The
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# standard deviation is 2.73. On a box with 64-bit hash
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# codes, no collisions are expected. Here we accept no
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# more than 15 collisions. Any worse and the hash function
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# is sorely suspect.
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N=50
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base = range(N)
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xp = [(i, j) for i in base for j in base]
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inps = base + [(i, j) for i in base for j in xp] + \
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[(i, j) for i in xp for j in base] + xp + zip(base)
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collisions = len(inps) - len(set(map(hash, inps)))
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self.assert_(collisions <= 15)
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def test_main():
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test_support.run_unittest(TupleTest)
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if __name__=="__main__":
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test_main()
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