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Darren Dale <dd55@×××××××.edu> (Sat, 22 Oct 2005 14:16:02 -0400): |
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> I am trying to track down the source of a bug in the SciPy development branch |
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> which, so far, has only been reported on a Gentoo platform (mine). It |
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> involves the use of the libc math function "signbit". Here is a clip from the |
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> manpage: |
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> |
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> `signbit' is a generic macro which can work on all real floating- |
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> point types. It returns a non-zero value if the value of X has |
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> its sign bit set. |
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> |
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> On my system, SciPy's signbit function reports that the sign bit is not set |
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> for any number, positive or negative. Could someone here help me understand |
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> how to test the libc signbit function? I have to admit I have no experience |
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> with C programming. |
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|
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Hello Darren, |
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|
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This doesn't have to be a bug. I don't know how SciPy works, but many |
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scientific libraries provide their own number types. In most number |
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encoding schemes (like floating point) the sign of a number is |
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determined by a single bit (the most significant bit of the whole |
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number, for integer types; the most significant bit of the mantissa, for |
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floating point types). |
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|
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The scheme could be totally different for SciPy, so the bit actually |
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reported might be the wrong bit. This is not a bug, but rather a |
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missing feature (signbit() doesn't know the type of the number). |
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|
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Regards. |
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----- |
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Get my public key via GnuPG with one of: |
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gpg --keyserver subkeys.pgp.net --recv-keys CE402012 |
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gpg --keyserver ldap://keyserver.pgp.com/ --recv-keys CE402012 |
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|
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Or via web-based keyserver: |
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http://www.keyserver.de/ |
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|
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Key fingerprint: |
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0F12 0912 DFC8 2FC5 E2B8 A23E 6BAC 998E CE40 2012 |
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