39 lines
840 B
C++
39 lines
840 B
C++
#include "nr.h"
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DP NR::ran2(int &idum)
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{
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const int IM1=2147483563,IM2=2147483399;
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const int IA1=40014,IA2=40692,IQ1=53668,IQ2=52774;
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const int IR1=12211,IR2=3791,NTAB=32,IMM1=IM1-1;
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const int NDIV=1+IMM1/NTAB;
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const DP EPS=3.0e-16,RNMX=1.0-EPS,AM=1.0/DP(IM1);
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static int idum2=123456789,iy=0;
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static Vec_INT iv(NTAB);
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int j,k;
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DP temp;
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if (idum <= 0) {
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idum=(idum==0 ? 1 : -idum);
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idum2=idum;
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for (j=NTAB+7;j>=0;j--) {
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k=idum/IQ1;
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idum=IA1*(idum-k*IQ1)-k*IR1;
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if (idum < 0) idum += IM1;
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if (j < NTAB) iv[j] = idum;
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}
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iy=iv[0];
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}
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k=idum/IQ1;
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idum=IA1*(idum-k*IQ1)-k*IR1;
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if (idum < 0) idum += IM1;
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k=idum2/IQ2;
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idum2=IA2*(idum2-k*IQ2)-k*IR2;
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if (idum2 < 0) idum2 += IM2;
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j=iy/NDIV;
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iy=iv[j]-idum2;
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iv[j] = idum;
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if (iy < 1) iy += IMM1;
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if ((temp=AM*iy) > RNMX) return RNMX;
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else return temp;
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}
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