#include "ran1.h" /* note #undef's at end of file */ /* returns a uniform random deviate between 0 and 1 (exclusive of the endpoint values)*/ /* call with idum a negative integer to initialize (if you use a positive integer the deviates you obtain is independet of the seed); * do not alter idum between successive deviates in a sequence * If the value of idum is not initialized you will always obtain the same deviates */ #define IA 16807 #define IM 2147483647 #define AM (1.0/IM) #define IQ 127773 #define IR 2836 #define NTAB 32 #define NDIV (1+(IM-1)/NTAB) #define EPS 1.2e-7 #define RNMX (1.0-EPS) float ran1(long *idum) /* ran1 ha in input un puntatore a long, ma poi nel codice sfrutta il valore puntato, non il suo indirizzo*/ { int j; long k; static long iy=0; static long iv[NTAB]; float temp; if (*idum <= 0 || !iy) { if (-(*idum) < 1) *idum=1; else *idum = -(*idum); for (j=NTAB+7;j>=0;j--) { k=(*idum)/IQ; *idum=IA*(*idum-k*IQ)-IR*k; if (*idum < 0) *idum += IM; if (j < NTAB) iv[j] = *idum; } iy=iv[0]; } k=(*idum)/IQ; *idum=IA*(*idum-k*IQ)-IR*k; if (*idum < 0) *idum += IM; j=iy/NDIV; iy=iv[j]; iv[j] = *idum; if ((temp=AM*iy) > RNMX) return RNMX; else return temp; } #undef IA #undef IM #undef AM #undef IQ #undef IR #undef NTAB #undef NDIV #undef EPS #undef RNMX