25 lines
483 B
C
25 lines
483 B
C
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#include <math.h>
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#define JMAX 20
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float rtnewt(void (*funcd)(float, float *, float *), float x1, float x2,
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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 df,dx,f,rtn;
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rtn=0.5*(x1+x2);
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for (j=1;j<=JMAX;j++) {
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(*funcd)(rtn,&f,&df);
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dx=f/df;
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rtn -= dx;
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if ((x1-rtn)*(rtn-x2) < 0.0)
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nrerror("Jumped out of brackets in rtnewt");
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if (fabs(dx) < xacc) return rtn;
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}
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nrerror("Maximum number of iterations exceeded in rtnewt");
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return 0.0;
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}
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#undef JMAX
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