67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
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#include <math.h>
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#define NRANSI
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#include "nrutil.h"
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#define TINY 1.0e-10
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#define NMAX 5000
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#define GET_PSUM \
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for (j=1;j<=ndim;j++) {\
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for (sum=0.0,i=1;i<=mpts;i++) sum += p[i][j];\
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psum[j]=sum;}
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#define SWAP(a,b) {swap=(a);(a)=(b);(b)=swap;}
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void amoeba(float **p, float y[], int ndim, float ftol,
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float (*funk)(float []), int *nfunk)
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{
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float amotry(float **p, float y[], float psum[], int ndim,
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float (*funk)(float []), int ihi, float fac);
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int i,ihi,ilo,inhi,j,mpts=ndim+1;
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float rtol,sum,swap,ysave,ytry,*psum;
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psum=vector(1,ndim);
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*nfunk=0;
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GET_PSUM
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for (;;) {
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ilo=1;
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ihi = y[1]>y[2] ? (inhi=2,1) : (inhi=1,2);
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for (i=1;i<=mpts;i++) {
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if (y[i] <= y[ilo]) ilo=i;
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if (y[i] > y[ihi]) {
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inhi=ihi;
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ihi=i;
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} else if (y[i] > y[inhi] && i != ihi) inhi=i;
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}
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rtol=2.0*fabs(y[ihi]-y[ilo])/(fabs(y[ihi])+fabs(y[ilo])+TINY);
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if (rtol < ftol) {
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SWAP(y[1],y[ilo])
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for (i=1;i<=ndim;i++) SWAP(p[1][i],p[ilo][i])
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break;
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}
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if (*nfunk >= NMAX) nrerror("NMAX exceeded");
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*nfunk += 2;
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ytry=amotry(p,y,psum,ndim,funk,ihi,-1.0);
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if (ytry <= y[ilo])
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ytry=amotry(p,y,psum,ndim,funk,ihi,2.0);
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else if (ytry >= y[inhi]) {
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ysave=y[ihi];
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ytry=amotry(p,y,psum,ndim,funk,ihi,0.5);
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if (ytry >= ysave) {
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for (i=1;i<=mpts;i++) {
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if (i != ilo) {
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for (j=1;j<=ndim;j++)
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p[i][j]=psum[j]=0.5*(p[i][j]+p[ilo][j]);
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y[i]=(*funk)(psum);
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}
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}
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*nfunk += ndim;
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GET_PSUM
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}
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} else --(*nfunk);
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}
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free_vector(psum,1,ndim);
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}
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#undef SWAP
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#undef GET_PSUM
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#undef NMAX
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#undef NRANSI
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