/* randist/logarithmic.c *  * Copyright (C) 1996, 1997, 1998, 1999, 2000 James Theiler, Brian Gough *  * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or (at * your option) any later version. *  * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * General Public License for more details. *  * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */#include <config.h>#include <math.h>#include <gsl/gsl_rng.h>#include <gsl/gsl_randist.h>/* Logarithmic distribution    prob(n) =   p^n / (n log(1/(1-p)) for n = 1, 2, 3, ...   We use Kemp's second accelerated generator, from Luc Devroye's book   on "Non-Uniform Random Variate Generation", Springer */unsigned intgsl_ran_logarithmic (const gsl_rng * r, const double p){  double c = log (1-p) ;  double v = gsl_rng_uniform_pos (r);    if (v >= p)    {      return 1 ;    }  else    {      double u = gsl_rng_uniform_pos (r);            double q = 1 - exp (c * u);      if (v <= q*q)        {          double x = 1 + log(v)/log(q) ;          return x ;        }      else if (v <= q)        {          return 2;        }      else        {          return 1 ;        }    }}doublegsl_ran_logarithmic_pdf (const unsigned int k, const double p){  if (k == 0)    {      return 0 ;    }  else     {      double P = pow(p, (double)k) / (double) k / log(1/(1-p)) ;      return P;    }}