45 lines
705 B
C
45 lines
705 B
C
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#include <math.h>
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#define R 0.61803399
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#define C (1.0-R)
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#define SHFT2(a,b,c) (a)=(b);(b)=(c);
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#define SHFT3(a,b,c,d) (a)=(b);(b)=(c);(c)=(d);
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float golden(ax,bx,cx,f,tol,xmin)
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float (*f)(),*xmin,ax,bx,cx,tol;
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{
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float f1,f2,x0,x1,x2,x3;
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x0=ax;
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x3=cx;
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if (fabs(cx-bx) > fabs(bx-ax)) {
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x1=bx;
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x2=bx+C*(cx-bx);
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} else {
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x2=bx;
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x1=bx-C*(bx-ax);
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}
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f1=(*f)(x1);
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f2=(*f)(x2);
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while (fabs(x3-x0) > tol*(fabs(x1)+fabs(x2))) {
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if (f2 < f1) {
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SHFT3(x0,x1,x2,R*x1+C*x3)
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SHFT2(f1,f2,(*f)(x2))
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} else {
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SHFT3(x3,x2,x1,R*x2+C*x0)
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SHFT2(f2,f1,(*f)(x1))
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}
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}
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if (f1 < f2) {
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*xmin=x1;
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return f1;
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} else {
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*xmin=x2;
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return f2;
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}
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}
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#undef C
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#undef R
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#undef SHFT2
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#undef SHFT3
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