double k_at(cow_domain *d, int i, int j, int k, double *kvec)
// -----------------------------------------------------------------------------
// Here, we populate the wave vectors on the Fourier lattice. The convention
// used by FFTW is the same as that used by numpy, described at the link
// below. For N odd, the (positive) Nyquist frequency is placed in the middle
// bin.
//
// http://docs.scipy.org/doc/numpy/reference/generated/numpy.fft.fftfreq.html
// -----------------------------------------------------------------------------
{
const int Nx = cow_domain_getnumglobalzones(d, 0);
const int Ny = cow_domain_getnumglobalzones(d, 1);
const int Nz = cow_domain_getnumglobalzones(d, 2);
i += cow_domain_getglobalstartindex(d, 0);
j += cow_domain_getglobalstartindex(d, 1);
k += cow_domain_getglobalstartindex(d, 2);
kvec[0] = (Nx % 2 == 0) ?
((i< Nx /2) ? i : i-Nx): // N even
((i<=(Nx-1)/2) ? i : i-Nx); // N odd
kvec[1] = (Ny % 2 == 0) ?
((j< Ny /2) ? j : j-Ny):
((j<=(Ny-1)/2) ? j : j-Ny);
kvec[2] = (Nz % 2 == 0) ?
((k< Nz /2) ? k : k-Nz):
((k<=(Nz-1)/2) ? k : k-Nz);
return sqrt(kvec[0]*kvec[0] + kvec[1]*kvec[1] + kvec[2]*kvec[2]);
}
void cow_dfield_sampleglobalind(cow_dfield *f, int i, int j, int k, double **x,
int *n0)
{
int ng = f->domain->n_ghst;
double xin[3];
i -= cow_domain_getglobalstartindex(f->domain, 0);
j -= cow_domain_getglobalstartindex(f->domain, 1);
k -= cow_domain_getglobalstartindex(f->domain, 2);
xin[0] = cow_domain_positionatindex(f->domain, 0, i + ng);
xin[1] = cow_domain_positionatindex(f->domain, 1, j + ng);
xin[2] = cow_domain_positionatindex(f->domain, 2, k + ng);
cow_dfield_setsamplecoords(f, xin, 1, 3);
cow_dfield_setsamplemode(f, COW_SAMPLE_NEAREST);
cow_dfield_sampleexecute(f);
cow_dfield_getsampleresult(f, x, NULL, n0);
}
struct fft_plan_3d *call_fft_plan_3d(cow_domain *d, int *nbuf)
{
const int i0 = cow_domain_getglobalstartindex(d, 0);
const int i1 = cow_domain_getnumlocalzonesinterior(d, 0) + i0 - 1;
const int j0 = cow_domain_getglobalstartindex(d, 1);
const int j1 = cow_domain_getnumlocalzonesinterior(d, 1) + j0 - 1;
const int k0 = cow_domain_getglobalstartindex(d, 2);
const int k1 = cow_domain_getnumlocalzonesinterior(d, 2) + k0 - 1;
const int Nx = cow_domain_getnumglobalzones(d, 0);
const int Ny = cow_domain_getnumglobalzones(d, 1);
const int Nz = cow_domain_getnumglobalzones(d, 2);
return fft_3d_create_plan(d->mpi_cart,
Nz, Ny, Nx,
k0,k1, j0,j1, i0,i1,
k0,k1, j0,j1, i0,i1,
SCALED_NOT, PERMUTE_NONE, nbuf);
}
