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#include <math.h>
#define PI 3.141592654
float poidev(float xm, int *idum)
{
float gammln(float xx);
float ran1(int *idum);
static float sq,alxm,g,oldm=(-1.0);
float em,t,y;
if (xm < 12.0) {
if (xm != oldm) {
oldm=xm;
g=exp(-xm);
}
em = -1;
t=1.0;
do {
++em;
t *= ran1(idum);
} while (t > g);
} else {
if (xm != oldm) {
oldm=xm;
sq=sqrt(2.0*xm);
alxm=log(xm);
g=xm*alxm-gammln(xm+1.0);
}
do {
do {
y=tan(PI*ran1(idum));
em=sq*y+xm;
} while (em < 0.0);
em=floor(em);
t=0.9*(1.0+y*y)*exp(em*alxm-gammln(em+1.0)-g);
} while (ran1(idum) > t);
}
return em;
}
float poidev_copy(float xm, int *idum)
{
float gammln(float xx);
float ran1_copy(int *idum);
static float sq1,alxm1,g1,oldm1=(-1.0);
float em,t,y;
if (xm < 12.0) {
if (xm != oldm1) {
oldm1=xm;
g1=exp(-xm);
}
em = -1;
t=1.0;
do {
++em;
t *= ran1_copy(idum);
} while (t > g1);
} else {
if (xm != oldm1) {
oldm1=xm;
sq1=sqrt(2.0*xm);
alxm1=log(xm);
g1=xm*alxm1-gammln(xm+1.0);
}
do {
do {
y=tan(PI*ran1_copy(idum));
em=sq1*y+xm;
} while (em < 0.0);
em=floor(em);
t=0.9*(1.0+y*y)*exp(em*alxm1-gammln(em+1.0)-g1);
} while (ran1_copy(idum) > t);
}
return em;
}
#undef PI
/* (C) Copr. 1986-92 Numerical Recipes Software )1!. */