Issue #1772851. Optimization of __hash__ to behave better for big big
numbers.
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@ -766,10 +766,17 @@ class Decimal(object):
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if self._isnan():
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raise TypeError('Cannot hash a NaN value.')
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return hash(str(self))
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i = int(self)
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if self == Decimal(i):
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return hash(i)
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assert self.__nonzero__() # '-0' handled by integer case
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if not self:
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return 0
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if self._isinteger():
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op = _WorkRep(self.to_integral_value())
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# to make computation feasible for Decimals with large
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# exponent, we use the fact that hash(n) == hash(m) for
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# any two nonzero integers n and m such that (i) n and m
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# have the same sign, and (ii) n is congruent to m modulo
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# 2**64-1. So we can replace hash((-1)**s*c*10**e) with
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# hash((-1)**s*c*pow(10, e, 2**64-1).
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return hash((-1)**op.sign*op.int*pow(10, op.exp, 2**64-1))
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return hash(str(self.normalize()))
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def as_tuple(self):
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@ -910,6 +910,38 @@ class DecimalUsabilityTest(unittest.TestCase):
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def test_hash_method(self):
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#just that it's hashable
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hash(Decimal(23))
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test_values = [Decimal(sign*(2**m + n))
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for m in [0, 14, 15, 16, 17, 30, 31,
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32, 33, 62, 63, 64, 65, 66]
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for n in range(-10, 10)
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for sign in [-1, 1]]
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test_values.extend([
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Decimal("-0"), # zeros
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Decimal("0.00"),
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Decimal("-0.000"),
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Decimal("0E10"),
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Decimal("-0E12"),
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Decimal("10.0"), # negative exponent
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Decimal("-23.00000"),
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Decimal("1230E100"), # positive exponent
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Decimal("-4.5678E50"),
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# a value for which hash(n) != hash(n % (2**64-1))
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# in Python pre-2.6
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Decimal(2**64 + 2**32 - 1),
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# selection of values which fail with the old (before
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# version 2.6) long.__hash__
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Decimal("1.634E100"),
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Decimal("90.697E100"),
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Decimal("188.83E100"),
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Decimal("1652.9E100"),
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Decimal("56531E100"),
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])
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# check that hash(d) == hash(int(d)) for integral values
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for value in test_values:
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self.assertEqual(hash(value), hash(int(value)))
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#the same hash that to an int
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self.assertEqual(hash(Decimal(23)), hash(23))
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self.assertRaises(TypeError, hash, Decimal('NaN'))
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