55 lines
862 B
C
55 lines
862 B
C
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#include <math.h>
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#include "nrutil.h"
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#define MF 3
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#define BI (1.0/256)
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void mpsqrt(w,u,v,n,m)
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int m,n;
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unsigned char u[],v[],w[];
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{
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void mplsh(),mpmov(),mpmul(),mpneg(),mpsdv();
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int i,ir,j,mm;
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float fu,fv;
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unsigned char *r,*s;
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r=cvector(1,n<<1);
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s=cvector(1,n<<1);
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mm=IMIN(m,MF);
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fv=(float) v[mm];
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for (j=mm-1;j>=1;j--) {
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fv *= BI;
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fv += v[j];
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}
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fu=1.0/sqrt(fv);
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for (j=1;j<=n;j++) {
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i=(int) fu;
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u[j]=(unsigned char) i;
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fu=256.0*(fu-i);
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}
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for (;;) {
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mpmul(r,u,u,n,n);
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mplsh(r,n);
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mpmul(s,r,v,n,IMIN(m,n));
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mplsh(s,n);
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mpneg(s,n);
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s[1] -= 253;
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mpsdv(s,s,n,2,&ir);
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for (j=2;j<n;j++) {
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if (s[j]) {
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mpmul(r,s,u,n,n);
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mpmov(u,&r[1],n);
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break;
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}
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}
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if (j<n) continue;
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mpmul(r,u,v,n,IMIN(m,n));
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mpmov(w,&r[1],n);
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free_cvector(s,1,n<<1);
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free_cvector(r,1,n<<1);
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return;
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}
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}
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#undef MF
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#undef BI
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