gammainc & GSL

[Teemu Ikonen]

I had some problems with the function gammainc which gives wrong results 
with large argument values (see my bugreport in bug-octave). When
investigating further I found out that the reason was that Octave is
trying to calculate gammainc by calling a fortran routine from SLATEC for
a slightly different form of the function (Tricomis form, 
x^-a * gammainc(x, a)) and then correcting the result, which fails with
large a and x.

I tried to dug a real implementation from the net and found a nice looking
one from GNU scientific library [1]. Adding GSL routines to Octave
isn't trivial because of GSL's error handling and other supporting
functions which would have to be changed to comply with Octave, but GSL
contains a lot of useful code (in C!), especially in the special functions
section, so we could have quite a lot more functionality as a result.

Now if I start to integrate GSL into libcruft, is there any chance that
the modifications could be included in the Octave distribution?

Teemu

[1] http://sources.redhat.com/gsl/