49 lines
777 B
C
49 lines
777 B
C
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#define MBIG 1000000000
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#define MSEED 161803398
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#define MZ 0
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#define FAC (1.0/MBIG)
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float ran3(idum)
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long *idum;
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{
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static int inext,inextp;
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static long ma[56];
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static int iff=0;
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long mj,mk;
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int i,ii,k;
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if (*idum < 0 || iff == 0) {
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iff=1;
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mj=labs(MSEED-labs(*idum));
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mj %= MBIG;
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ma[55]=mj;
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mk=1;
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for (i=1;i<=54;i++) {
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ii=(21*i) % 55;
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ma[ii]=mk;
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mk=mj-mk;
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if (mk < MZ) mk += MBIG;
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mj=ma[ii];
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}
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for (k=1;k<=4;k++)
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for (i=1;i<=55;i++) {
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ma[i] -= ma[1+(i+30) % 55];
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if (ma[i] < MZ) ma[i] += MBIG;
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}
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inext=0;
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inextp=31;
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*idum=1;
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}
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if (++inext == 56) inext=1;
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if (++inextp == 56) inextp=1;
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mj=ma[inext]-ma[inextp];
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if (mj < MZ) mj += MBIG;
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ma[inext]=mj;
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return mj*FAC;
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}
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#undef MBIG
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#undef MSEED
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#undef MZ
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#undef FAC
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