new randist/binomial.c

[Brian Gough]

James Theiler writes:
 > Hello,
 >   Awhile back I wrote about how much slower the GSL binomial random
 > variates were than competing algorithms -- thanks again to John
 > Pearson for first pointing this out to me.
 >   I have attached new code for binomial variates which incorporates a
 > state of the art algorithm

Thanks. I'm looking at integrating it.  

 >   3. I have added a new function gsl_ran_binomial_cdf(), which is the
 > cumulative distribution function (akin to the pdf).  I think we should
 > begin filling out the cdf's for all our nonuniform variates.

There are some cdfs in cvs on savannah.gnu.org (none for the
discrete distributions though).

 >   4. Just a quick note, I got a substantial performance gain using
 > gsl_sf_pow_int() in place of pow(), even for very large powers.  GSL
 > developers might keep that in mind when performing x^n type
 > computations.  By the way, I noticed GSL also has a gsl_pow_int()
 > with essentially the same implementation in the sys/pow_int.c file;
 > which is preferred?

gsl_pow_int is preferred. It's part of gsl_pow_int.h (which is
#included by gsl_math.h).

Brian