test_pow is failing on the alpha Debian buildbot, complaining that a
negative number can't be raised to a fractional power. Now, to work
around some bugs in platform implementations of math.fpow(), pow() does
its own check to see if the exponent is an integer.
The way pow() does that check is to try "iw == floor(iw)", so to see why
the exception was being triggered, I put a couple of extra output lines
into the test and got:
*** Number: 1.2299999999999999e+167
*** Floor: 1.2299999999999997e+167
Given that the magnitude of the exponent significantly exceeds the
precision of an IEEE double, it seems wrong for floor() to be changing
the mantissa like that (and, on my machine, and all of the other
buildbots, it doesn't).
I've added an explicit test for this misbehaviour to test_math so at
least the buildbot gives a clearer indication of what's going wrong, but
I'm not sure what to do with it beyond that.
Cheers,
Nick.
--
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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