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32 lines
741 B
C
32 lines
741 B
C
#include <math.h>
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#include "genlib.h"
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#define NTAB 32
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double gasdev(long *idum,long *idum2, long *iy, long iv[NTAB])
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/*returns a normally distributed deviate with 0 mean*/
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/*and unit variance, using ran2(idum) as the source */
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/*of uniform deviates */
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{
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double ran2(long *idum,long *idum2, long *iy, long iv[NTAB]);
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static int iset = 0;
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static double gset;
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double fac,rsq,v1,v2;
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if (iset == 0) {
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do {
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v1 = 2.0*ran2(idum,idum2,iy,iv)-1.0;
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v2 = 2.0*ran2(idum,idum2,iy,iv)-1.0;
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rsq = v1*v1+v2*v2;
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} while (rsq >= 1.0 || rsq == 0.0);
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fac = sqrt(-2.0*log(rsq)/rsq);
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gset = v1*fac;
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iset = 1;
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return (v2*fac);
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} else {
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iset = 0;
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return (gset);
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}
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}
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