66 lines
1.1 KiB
C++
66 lines
1.1 KiB
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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namespace {
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inline void shft3(DP &a, DP &b, DP &c, const DP d)
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{
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a=b;
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b=c;
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c=d;
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}
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}
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void NR::mnbrak(DP &ax, DP &bx, DP &cx, DP &fa, DP &fb, DP &fc,
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DP func(const DP))
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{
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const DP GOLD=1.618034,GLIMIT=100.0,TINY=1.0e-20;
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DP ulim,u,r,q,fu;
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fa=func(ax);
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fb=func(bx);
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if (fb > fa) {
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SWAP(ax,bx);
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SWAP(fb,fa);
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}
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cx=bx+GOLD*(bx-ax);
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fc=func(cx);
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while (fb > fc) {
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r=(bx-ax)*(fb-fc);
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q=(bx-cx)*(fb-fa);
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u=bx-((bx-cx)*q-(bx-ax)*r)/
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(2.0*SIGN(MAX(fabs(q-r),TINY),q-r));
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ulim=bx+GLIMIT*(cx-bx);
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if ((bx-u)*(u-cx) > 0.0) {
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fu=func(u);
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if (fu < fc) {
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ax=bx;
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bx=u;
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fa=fb;
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fb=fu;
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return;
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} else if (fu > fb) {
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cx=u;
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fc=fu;
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return;
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}
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u=cx+GOLD*(cx-bx);
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fu=func(u);
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} else if ((cx-u)*(u-ulim) > 0.0) {
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fu=func(u);
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if (fu < fc) {
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shft3(bx,cx,u,cx+GOLD*(cx-bx));
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shft3(fb,fc,fu,func(u));
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}
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} else if ((u-ulim)*(ulim-cx) >= 0.0) {
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u=ulim;
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fu=func(u);
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} else {
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u=cx+GOLD*(cx-bx);
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fu=func(u);
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}
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shft3(ax,bx,cx,u);
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shft3(fa,fb,fc,fu);
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}
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}
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