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add support for Huffenberger & Wandelt grid

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This commit is contained in:
Martin Reinecke 2012-11-19 17:10:19 +01:00
parent 5d486e11bc
commit 7a99085e38
3 changed files with 81 additions and 2 deletions
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54
libsharp/sharp_geomhelpers.c
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@ -25,7 +25,7 @@
/*! \file sharp_geomhelpers.c
* Spherical transform library
*
* Copyright (C) 2006-2011 Max-Planck-Society
* Copyright (C) 2006-2012 Max-Planck-Society
* Copyright (C) 2007-2008 Pavel Holoborodko (for gauss_legendre_tbl)
* \author Martin Reinecke \author Pavel Holoborodko
*/
@ -241,3 +241,55 @@ void sharp_make_ecp_geom_info (int nrings, int nphi, double phi0,
DEALLOC(ofs);
DEALLOC(stride_);
}
static double eps(int j, int J)
{
if ((j==0)||(j==J)) return 0.5;
if ((j>0)&&(j<J)) return 1.;
return 0.;
}
/* Weights from Keiner & Potts: "Fast evaluation of quadrature formulae
on the sphere", 2000 */
/* nrings MUST be odd */
void sharp_make_hw_geom_info (int nrings, int ppring, double phi0,
int stride_lon, int stride_lat, sharp_geom_info **geom_info)
{
const double pi=3.141592653589793238462643383279502884197;
double *theta=RALLOC(double,nrings);
double *weight=RALLOC(double,nrings);
int *nph=RALLOC(int,nrings);
double *phi0_=RALLOC(double,nrings);
ptrdiff_t *ofs=RALLOC(ptrdiff_t,nrings);
int *stride_=RALLOC(int,nrings);
UTIL_ASSERT((nrings&1)==1,"nrings must be an odd number");
int lmax=(nrings-1)/2;
for (int m=0; m<nrings; ++m)
{
theta[m]=pi*m/(nrings-1.);
if (theta[m]<1e-15) theta[m]=1e-15;
if (theta[m]>pi-1e-15) theta[m]=pi-1e-15;
nph[m]=ppring;
phi0_[m]=phi0;
ofs[m]=(ptrdiff_t)m*stride_lat;
stride_[m]=stride_lon;
double wgt=0;
double prefac=4*pi*eps(m,2*lmax)/lmax;
for (int l=0; l<=lmax; ++l)
wgt+=eps(l,lmax)/(1-4*l*l)*cos((pi*m*l)/lmax);
weight[m]=prefac*wgt/nph[m];
}
sharp_make_geom_info (nrings, nph, ofs, stride_, phi0_, theta, NULL, weight,
geom_info);
DEALLOC(theta);
DEALLOC(weight);
DEALLOC(nph);
DEALLOC(phi0_);
DEALLOC(ofs);
DEALLOC(stride_);
}