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Issue #12080: Fix a performance issue in Decimal._power_exact that causes some corner-case Decimal.__pow__ calls to take an unreasonably long time.

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This commit is contained in:
Mark Dickinson 2011-06-04 18:14:23 +01:00
parent 4dfcb1a00d
commit 7ce0fa8775
3 changed files with 96 additions and 37 deletions
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13
Lib/test/decimaltestdata/extra.decTest
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@ -222,12 +222,25 @@ extr1700 power 10 1e-999999999 -> 1.000000000000000 Inexact Rounded
extr1701 power 100.0 -557.71e-742888888 -> 1.000000000000000 Inexact Rounded
extr1702 power 10 1e-100 -> 1.000000000000000 Inexact Rounded
-- Another one (see issue #12080). Thanks again to Stefan Krah.
extr1703 power 4 -1.2e-999999999 -> 1.000000000000000 Inexact Rounded
-- A couple of interesting exact cases for power. Note that the specification
-- requires these to be reported as Inexact.
extr1710 power 1e375 56e-3 -> 1.000000000000000E+21 Inexact Rounded
extr1711 power 10000 0.75 -> 1000.000000000000 Inexact Rounded
extr1712 power 1e-24 0.875 -> 1.000000000000000E-21 Inexact Rounded
-- Some more exact cases, exercising power with negative second argument.
extr1720 power 400 -0.5 -> 0.05000000000000000 Inexact Rounded
extr1721 power 4096 -0.75 -> 0.001953125000000000 Inexact Rounded
extr1722 power 625e4 -0.25 -> 0.02000000000000000 Inexact Rounded
-- Nonexact cases, to exercise some of the early exit conditions from
-- _power_exact.
extr1730 power 2048 -0.75 -> 0.003284751622084822 Inexact Rounded
-- Tests for the is_* boolean operations
precision: 9
maxExponent: 999