44 lines
714 B
C
44 lines
714 B
C
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#include <math.h>
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#define MAXIT 30
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float rtflsp(float (*func)(float), float x1, float x2, float xacc)
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{
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void nrerror(char error_text[]);
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int j;
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float fl,fh,xl,xh,swap,dx,del,f,rtf;
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fl=(*func)(x1);
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fh=(*func)(x2);
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if (fl*fh > 0.0) nrerror("Root must be bracketed in rtflsp");
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if (fl < 0.0) {
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xl=x1;
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xh=x2;
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} else {
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xl=x2;
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xh=x1;
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swap=fl;
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fl=fh;
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fh=swap;
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}
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dx=xh-xl;
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for (j=1;j<=MAXIT;j++) {
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rtf=xl+dx*fl/(fl-fh);
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f=(*func)(rtf);
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if (f < 0.0) {
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del=xl-rtf;
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xl=rtf;
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fl=f;
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} else {
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del=xh-rtf;
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xh=rtf;
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fh=f;
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}
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dx=xh-xl;
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if (fabs(del) < xacc || f == 0.0) return rtf;
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}
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nrerror("Maximum number of iterations exceeded in rtflsp");
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return 0.0;
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}
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#undef MAXIT
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