50 lines
829 B
C
50 lines
829 B
C
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#include <math.h>
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#define SWAP(a,b) {dum=(a);(a)=(b);(b)=dum;}
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#define TINY 1.0e-20
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void bandec(a,n,m1,m2,al,indx,d)
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float **a,**al,*d;
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int m1,m2;
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unsigned long indx[],n;
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{
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unsigned long i,j,k,l;
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int mm;
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float dum;
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mm=m1+m2+1;
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l=m1;
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for (i=1;i<=m1;i++) {
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for (j=m1+2-i;j<=mm;j++) a[i][j-l]=a[i][j];
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l--;
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for (j=mm-l;j<=mm;j++) a[i][j]=0.0;
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}
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*d=1.0;
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l=m1;
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for (k=1;k<=n;k++) {
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dum=a[k][1];
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i=k;
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if (l < n) l++;
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for (j=k+1;j<=l;j++) {
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if (fabs(a[j][1]) > fabs(dum)) {
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dum=a[j][1];
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i=j;
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}
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}
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indx[k]=i;
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if (dum == 0.0) a[k][1]=TINY;
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if (i != k) {
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*d = -(*d);
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for (j=1;j<=mm;j++) SWAP(a[k][j],a[i][j])
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}
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for (i=k+1;i<=l;i++) {
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dum=a[i][1]/a[k][1];
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al[k][i-k]=dum;
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for (j=2;j<=mm;j++) a[i][j-1]=a[i][j]-dum*a[k][j];
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a[i][mm]=0.0;
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}
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}
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}
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#undef SWAP
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#undef TINY
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