50 lines
770 B
C++
50 lines
770 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::mpsqrt(Vec_O_UCHR &w, Vec_O_UCHR &u, Vec_I_UCHR &v)
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{
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const int MF=3;
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const DP BI=1.0/256.0;
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int i,ir,j,mm;
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DP fu,fv;
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int n=u.size();
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int m=v.size();
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Vec_UCHR r(2*n),x(n+m),s(2*n+m),t(3*n+m);
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mm=MIN(m,MF);
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fv=DP(v[mm-1]);
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for (j=mm-2;j>=0;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=0;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);
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mplsh(r);
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mpmul(s,r,v);
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mplsh(s);
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mpneg(s);
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s[0] += (unsigned char) 3;
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mpsdv(s,s,2,ir);
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for (j=1;j<n-1;j++) {
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if (s[j] != 0) {
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mpmul(t,s,u);
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mplsh(t);
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mpmov(u,t);
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break;
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}
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}
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if (j<n-1) continue;
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mpmul(x,u,v);
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mplsh(x);
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mpmov(w,x);
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return;
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}
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}
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