[SciPy-user] special.jn(3,x) became inexact in recent versions

Amit Aronovitch aronovitch at gmail.com
Sun Jan 21 15:07:58 CST 2007


Robert Kern wrote:
> 
> And several other C runtimes as well. For some reason I was under the impression
> that at least j0 was part of the C99 standard, but I do not see any of the
> Bessel functions in the standard itself (section 7.12):
> 
>   http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf
> 
> It would be possible to check for each of these and construct a configuration
> header with HAVE_LIBM_JN #defines. The #define hackery that renames jn to
> cephes_jn would be conditional on the HAVE_LIBM settings.
> 
> I hesitate to add more to the configuration steps, though. Better all around
> would be for us to find (or write) a suitably licensed implementation that's better.
> 
The code for these functions in glibc seems to be related (and almost
identical to) Sun's "unbundled" libm, which is freely available from netlib:
  http://www.netlib.org/fdlibm/
(not sure about the exact ancestry - possibly came through NetBSD)

I've no idea how it compares to cephes, but I see no problems with the
license. Might be worth running some benchmarks.
   Regards,
      AA



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