35 lines
541 B
C
35 lines
541 B
C
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#include <math.h>
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float gamdev(ia,idum)
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int ia;
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long *idum;
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{
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float ran1();
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void nrerror();
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int j;
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float am,e,s,v1,v2,x,y;
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if (ia < 1) nrerror("Error in routine gamdev");
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if (ia < 6) {
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x=1.0;
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for (j=1;j<=ia;j++) x *= ran1(idum);
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x = -log(x);
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} else {
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do {
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do {
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do {
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v1=ran1(idum);
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v2=2.0*ran1(idum)-1.0;
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} while (v1*v1+v2*v2 > 1.0);
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y=v2/v1;
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am=ia-1;
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s=sqrt(2.0*am+1.0);
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x=s*y+am;
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} while (x <= 0.0);
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e=(1.0+y*y)*exp(am*log(x/am)-s*y);
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} while (ran1(idum) > e);
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}
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return x;
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}
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