[issue27761] Private _nth_root function loses accuracy

[Martin Panter]

Martin Panter added the comment:

The problem is more widespread than just Power PC. The same failures (+/-29) are also seen on the three s390x buildbots. There are multiple failures of testExactPowers(Negatives) on
http://buildbot.python.org/all/builders/x86%20Tiger%203.x/builds/11140/steps/test/logs/stdio

The first is
AssertionError: 9.000000000000002 != 9

An slightly different failure happens on AMD64 Free BSD and Open Indiana buildbots:
http://buildbot.python.org/all/builders/AMD64%20OpenIndiana%203.x/builds/11077/steps/test/logs/stdio
======================================================================
FAIL: testFraction (test.test_statistics.Test_Nth_Root)
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Traceback (most recent call last):
  File "/export/home/buildbot/64bits/3.x.cea-indiana-amd64/build/Lib/test/test_statistics.py", line 1247, in testFraction
    self.assertEqual(self.nroot(x**12, 12), float(x))
AssertionError: 1.1866666666666665 != 1.1866666666666668

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title: Private _nth_root function loses accuracy on PowerPC -> Private _nth_root function loses accuracy

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27761>
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