29 lines
791 B
C++
29 lines
791 B
C++
#include "nr.h"
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void NR::daub4(Vec_IO_DP &a, const int n, const int isign)
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{
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const DP C0=0.4829629131445341,C1=0.8365163037378079,
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C2=0.2241438680420134,C3=-0.1294095225512604;
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int nh,i,j;
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if (n < 4) return;
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Vec_DP wksp(n);
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nh=n >> 1;
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if (isign >= 0) {
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for (i=0,j=0;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-2]+C1*a[n-1]+C2*a[0]+C3*a[1];
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wksp[i+nh]=C3*a[n-2]-C2*a[n-1]+C1*a[0]-C0*a[1];
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} else {
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wksp[0]=C2*a[nh-1]+C1*a[n-1]+C0*a[0]+C3*a[nh];
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wksp[1]=C3*a[nh-1]-C0*a[n-1]+C1*a[0]-C2*a[nh];
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for (i=0,j=2;i<nh-1;i++) {
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wksp[j++]=C2*a[i]+C1*a[i+nh]+C0*a[i+1]+C3*a[i+nh+1];
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wksp[j++]=C3*a[i]-C0*a[i+nh]+C1*a[i+1]-C2*a[i+nh+1];
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}
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}
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for (i=0;i<n;i++) a[i]=wksp[i];
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}
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