On 05/31/12 10:45, John Baldwin wrote:
On Monday, May 28, 2012 7:02:18 pm Steve Kargl wrote:
On Tue, May 29, 2012 at 07:05:07AM +1000, Peter Jeremy wrote:
On 2012-May-28 11:01:24 -0500, Stephen Montgomery-Smith
<step...@missouri.edu> wrote:
One thing that could be done is to have a "math/cephes" port that adds
the extra C99 math functions. This is already done in the math/sage
port, using a rather clever patch due to Peter Jeremy, that applies to
the cephes code.
What it would do is to create a /usr/local/lib/libm.so that would
provide the extra functions not currently included in /lib/libm.so, and
then link in /lib/libm.so as well. It would also create its own
/usr/local/include/math.h and /usr/local/include/complex.h as well.
Basically, as long as the compiler searches /usr/local/{include,lib}
before the base include/lib then<math.h>,<complex.h> and -lm give
the application a complete C99 math implementation by using base
functions where they exist and cephes functions where they don't.
The patch I wrote for sage can be found at
http://trac.sagemath.org/sage_trac/ticket/9543
If there's any interest, I could produce a port for this.
Another option would be to import cephes into base and use it to
provide the missing C99 functions. Cephes includes copyright notices
but the closest I can find to a license is:
" Some software in this archive may be from the book _Methods and
Programs for Mathematical Functions_ (Prentice-Hall or Simon& Schuster
International, 1989) or from the Cephes Mathematical Library, a
commercial product. In either event, it is copyrighted by the author.
What you see here may be used freely but it comes with no support or
guarantee."
Please talk to das@ (although I believe he's finishing up his
dissertation). I recall that he's stated that he looked into
using cephes, and concluded that it is not suitable for libm.
Note there is also
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/147599
which I've also objected to importing into libm.
I do think we should provide something in ports as an interim solution.
There are other 3rd party applications looking to drop FreeBSD support
because we are missing APIs that almost all other OS's have. I'm fine
if the interim lives in ports and that we don't import substandard
routines into the base. I would even be fine with calling it
/usr/local/lib/libm_inaccurate.so. However, I do think we need an option.
I think it should be called libm.so. Otherwise we have to do a serious
editing job on the Makefiles/configure scripts.
sed -E 's/[[:<:]]-lm[[:>:]]/-lm_inaccuarate/'
might have some false positives and false negatives. (Did I even get
the sed syntax correct?)
By the way, I was looking through:
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/147599
They say they compute cosh(2y) - cos(2x) using Taylor's series. I would
agree with Steve that this is seriously low quality. Floating point
errors are likely to be truly horrible. This will fail even for
non-edge cases. (This was the same error that openoffice used to have
for computing erf(x), that gave things like erf(100) = -4353243242.)
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