46 lines
859 B
C
46 lines
859 B
C
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#include <math.h>
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#define EPS 3.0e-14
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#define MAXIT 10
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void gaulag(x,w,n,alf)
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float alf,w[],x[];
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int n;
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{
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float gammln();
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void nrerror();
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int i,its,j;
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float ai;
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double p1,p2,p3,pp,z,z1;
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for (i=1;i<=n;i++) {
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if (i == 1) {
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z=(1.0+alf)*(3.0+0.92*alf)/(1.0+2.4*n+1.8*alf);
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} else if (i == 2) {
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z += (15.0+6.25*alf)/(1.0+0.9*alf+2.5*n);
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} else {
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ai=i-2;
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z += ((1.0+2.55*ai)/(1.9*ai)+1.26*ai*alf/
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(1.0+3.5*ai))*(z-x[i-2])/(1.0+0.3*alf);
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}
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for (its=1;its<=MAXIT;its++) {
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p1=1.0;
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p2=0.0;
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for (j=1;j<=n;j++) {
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p3=p2;
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p2=p1;
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p1=((2*j-1+alf-z)*p2-(j-1+alf)*p3)/j;
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}
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pp=(n*p1-(n+alf)*p2)/z;
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z1=z;
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z=z1-p1/pp;
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if (fabs(z-z1) <= EPS) break;
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}
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if (its > MAXIT) nrerror("too many iterations in gaulag");
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x[i]=z;
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w[i] = -exp(gammln(alf+n)-gammln((float)n))/(pp*n*p2);
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}
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}
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#undef EPS
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#undef MAXIT
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