Re: [Numpy-discussion] Portable functions for nans, signbit, etc.
On Thu, Oct 2, 2008 at 11:41 AM, Charles R Harris [EMAIL PROTECTED] wrote: Which is rather clever. I think binary_cast will require some pointer abuse. Yep (the funny thing is that the bit twiddling will likely end up more readable than this C++ stuff) cheers, David ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Portable functions for nans, signbit, etc.
On Thu, Oct 2, 2008 at 2:41 AM, David Cournapeau [EMAIL PROTECTED] wrote: On Thu, Oct 2, 2008 at 11:41 AM, Charles R Harris [EMAIL PROTECTED] wrote: Which is rather clever. I think binary_cast will require some pointer abuse. Yep (the funny thing is that the bit twiddling will likely end up more readable than this C++ stuff) The zip file has the bit twiddling, which is worth looking at if only for the note on the PPC extended precision. Motorola seems to be a problem but I don't think we support any of the 66xx series. Chuck ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
[Numpy-discussion] Portable functions for nans, signbit, etc.
The normal signbit function of gcc without the -std=c99 flag doesn't work
correctly for nans and infs. I found the following code on a boost mailing
list and it might be helpful here for portability.
const boost::uint32_t signbit_mask
= binary_castboost::uint32_t(1.0f)
^ binary_castboost::uint32_t(-1.0f);
inline bool signbit(float x)
{
return binary_castboost::uint32_t(x) signbit_mask;
}
inline bool signbit(double x)
{
return signbit(static_castfloat(x));
}
inline bool signbit(long double x)
{
return signbit(static_castfloat(x));
}
Which is rather clever. I think binary_cast will require some pointer abuse.
There are a bunch of other boost functions here
http://tinyurl.com/3tvj9uthat might prove useful. This file
goog_1222871357985floating_point_utilities_v3.zip
http://www.boostpro.com/vault/index.php?action=downloadfilefilename=floating_point_utilities_v3.zipdirectory=Math%20-%20NumericsPHPSESSID=64b789bb8092caa29b11839ec7526611
portable isnan, fpclassify, signbit etc. + facets for portable handling of
infinity and NaN in text streams
Looks particularly interesting. It's a bit large for the mailing list so I
won't attach it. The Boost license should be compatible with numpy.
Chuck
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