41 lines
914 B
C
41 lines
914 B
C
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#include "nrutil.h"
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#define C0 0.4829629131445341
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#define C1 0.8365163037378079
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#define C2 0.2241438680420134
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#define C3 -0.1294095225512604
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void daub4(a,n,isign)
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float a[];
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int isign;
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unsigned long n;
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{
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float *wksp;
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unsigned long nh,nh1,i,j;
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if (n < 4) return;
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wksp=vector(1,n);
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nh1=(nh=n >> 1)+1;
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if (isign >= 0) {
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for (i=1,j=1;j<=n-3;j+=2,i++) {
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wksp[i]=C0*a[j]+C1*a[j+1]+C2*a[j+2]+C3*a[j+3];
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wksp[i+nh] = C3*a[j]-C2*a[j+1]+C1*a[j+2]-C0*a[j+3];
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}
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wksp[i]=C0*a[n-1]+C1*a[n]+C2*a[1]+C3*a[2];
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wksp[i+nh] = C3*a[n-1]-C2*a[n]+C1*a[1]-C0*a[2];
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} else {
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wksp[1]=C2*a[nh]+C1*a[n]+C0*a[1]+C3*a[nh1];
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wksp[2] = C3*a[nh]-C0*a[n]+C1*a[1]-C2*a[nh1];
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for (i=1,j=3;i<nh;i++) {
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wksp[j++]=C2*a[i]+C1*a[i+nh]+C0*a[i+1]+C3*a[i+nh1];
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wksp[j++] = C3*a[i]-C0*a[i+nh]+C1*a[i+1]-C2*a[i+nh1];
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}
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}
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for (i=1;i<=n;i++) a[i]=wksp[i];
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free_vector(wksp,1,n);
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}
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#undef C0
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#undef C1
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#undef C2
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#undef C3
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