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36 lines
813 B
C
36 lines
813 B
C
#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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void splint(double xa[], double ya[], double y2a[], int n, double x, double *y)
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{
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void nrerror(char error_text[]);
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int klo,khi,k,i;
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double h,b,a;
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klo=1;
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khi=n;
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while (khi-klo > 1) {
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k=(khi+klo) >> 1;
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if (xa[k] > x) khi=k;
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else klo=k;
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}
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h=xa[khi]-xa[klo];
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if(h == 0.0) {
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printf("BADXA %d %f\n",n,x);
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fflush(stdout);
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}
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if (h == 0.0) nrerror("Bad xa input to routine splint");
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a=(xa[khi]-x)/h;
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b=(x-xa[klo])/h;
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*y=a*ya[klo]+b*ya[khi]+((a*a*a-a)*y2a[klo]+(b*b*b-b)*y2a[khi])*(h*h)/6.0;
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if(isnan(*y))
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{
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/*
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fprintf(stdout,"NAN %e %e %d %e %e %e %e %e %e\n",a,b,n,x,ya[klo],ya[khi],
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y2a[khi],y2a[klo],h);
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for(i=1;i<=n;++i)
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printf("NAN %d %e %e %e %e\n",i,xa[i],ya[i],y2a[i],x);
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*/
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*y=0;
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}
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}
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