Issue #1772851. Optimization of __hash__ to behave better for big big
numbers.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 4137d06..6ca8bab 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -766,10 +766,17 @@
if self._isnan():
raise TypeError('Cannot hash a NaN value.')
return hash(str(self))
- i = int(self)
- if self == Decimal(i):
- return hash(i)
- assert self.__nonzero__() # '-0' handled by integer case
+ if not self:
+ return 0
+ if self._isinteger():
+ op = _WorkRep(self.to_integral_value())
+ # to make computation feasible for Decimals with large
+ # exponent, we use the fact that hash(n) == hash(m) for
+ # any two nonzero integers n and m such that (i) n and m
+ # have the same sign, and (ii) n is congruent to m modulo
+ # 2**64-1. So we can replace hash((-1)**s*c*10**e) with
+ # hash((-1)**s*c*pow(10, e, 2**64-1).
+ return hash((-1)**op.sign*op.int*pow(10, op.exp, 2**64-1))
return hash(str(self.normalize()))
def as_tuple(self):