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switch to FFT for weight generation

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This commit is contained in:
Martin Reinecke 2012-11-26 23:34:08 +01:00
parent 94c6a99ad8
commit c631d58b24
1 changed files with 17 additions and 7 deletions
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24
libsharp/sharp_geomhelpers.c
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@ -31,8 +31,10 @@
*/
#include <math.h>
#include <complex.h>
#include "sharp_geomhelpers.h"
#include "c_utils.h"
#include "ls_fft.h"
void sharp_make_healpix_geom_info (int nside, int stride,
sharp_geom_info **geom_info)
@ -101,7 +103,7 @@ void sharp_make_weighted_healpix_geom_info (int nside, int stride,
}
static inline double one_minus_x2 (double x)
{ return (fabs(x)>0.1) ? (1+x)*(1-x) : 1.-x*x; }
{ return (fabs(x)>0.1) ? (1.+x)*(1.-x) : 1.-x*x; }
/* Function adapted from GNU GSL file glfixed.c
Original author: Pavel Holoborodko (http://www.holoborodko.com)
@ -204,6 +206,18 @@ void sharp_make_ecp_geom_info (int nrings, int ppring, double phi0,
double *phi0_=RALLOC(double,nrings);
ptrdiff_t *ofs=RALLOC(ptrdiff_t,nrings);
int *stride_=RALLOC(int,nrings);
complex double *cwgt=RALLOC(complex double, nrings);
cwgt[0]=2.;
for (int k=1; k<=(nrings-1)/2; ++k)
{
cwgt[k]=2./(1.-4.*k*k)*cexp(_Complex_I*((k*pi)/nrings));
cwgt[nrings-k]=conj(cwgt[k]);
}
if ((nrings&1)==0) cwgt[nrings/2]=0.;
complex_plan plan = make_complex_plan(nrings);
complex_plan_backward(plan,(double *)cwgt);
kill_complex_plan(plan);
for (int m=0; m<(nrings+1)/2; ++m)
{
@ -214,17 +228,13 @@ void sharp_make_ecp_geom_info (int nrings, int ppring, double phi0,
ofs[m]=(ptrdiff_t)m*stride_lat;
ofs[nrings-1-m]=(ptrdiff_t)((nrings-1-m)*stride_lat);
stride_[m]=stride_[nrings-1-m]=stride_lon;
double wgt=0;
int n=nrings;
for (int j=1; j<=n/2; ++j)
wgt += cos(((j*(2*m+1))%(2*n))*(pi/nrings))/(4.*j*j-1.);
wgt = 2./n*(1.-2*wgt)*2*pi/nph[m];
weight[m]=weight[nrings-1-m]=wgt;
weight[m]=weight[nrings-1-m]=creal(cwgt[m])*(2*pi/(nrings*nph[m]));
}
sharp_make_geom_info (nrings, nph, ofs, stride_, phi0_, theta, NULL, weight,
geom_info);
DEALLOC(cwgt);
DEALLOC(theta);
DEALLOC(weight);
DEALLOC(nph);