Delta::Delta(int _N, double _L, int _nover, double thresh, Mask3D& _mask)
// RS 2010/07/06: Comments!
{
// Cache values
N=_N; L=_L; nover=_nover; maskptr=&_mask; rmasksmooth = 0.0;
// Set up the density
// RS: dg2 is some kind of local variable; dg1 is a class member.
// W and _W are contents of a grid of the same size and dimensions
// as dg1 and dg2.
DensityGrid dg2(N, L);
dg1.Init(N, L);
_W = dg1.Allocate();
W = dg1.Allocate(); VecSet(W, 0.0);
// Now do the randoms
// RS: "Doing" the randoms in this context means "oversampling" each grid
// cell into subcells, where the main cell is nover times as large as each
// subcell and hence there are nover^3 subcells to a cell.
nrand=0.0;
double nexp, nthresh;
nexp = pow((double) nover, 3);
// RS: thresh is the *fraction* of the main cell's volume to be included
// inside the mask for it to be counted as not masked, so nthresh is the
// corresponding number of subcells.
nthresh = nexp*thresh;
{
double tmp = 1./nover, dx, dy, dz;
VecSet(_W, 0.0); // Manually set to zero
Vec W1; VecDuplicate(_W, &W1);
// RS: Loop over all subcell *offsets*. The loop over actual grid cells
// is implicit in the calls to methods like GridInitialize below.
for (int ix = 0; ix < nover; ++ix) {
PetscPrintf(PETSC_COMM_WORLD,"Starting random loop %i of %i....\n",ix,nover-1);
dx = ix*tmp + tmp/2.0;
for (int iy = 0; iy < nover; ++iy) {
dy = iy*tmp + tmp/2.0;
for (int iz = 0; iz < nover; ++iz) {
dz = iz*tmp + tmp/2.0;
Particle rr; // Definition here is important, since it ensures destruction, before recreating
// RS: Generate a bunch of particles uniformly spaced, and offset
// from the low-(x,y,z) corner of each grid cell by (dx,dy,dz).
rr.GridInitialize(N, dx, dy, dz, L);
// RS: Remove from the list any particles which were not allowed
// by the mask. Add to the total.
rr.TrimMask(*maskptr); nrand += rr.npart;
// rr.SlabDecompose(dg2); We don't need to slab decompose because nproc divides N by construction
// RS: CIC assign remaining particles to temporary grid vector W1.
dg1.CIC(W1, rr, false); // No overdensity
// RS: Now add to _W the CIC contents of W1.
VecAXPY(_W, 1.0, W1);
}
}
}
}
// RS: At this point, nrand equals the total number of oversampled subcells
// found to be allowed by the masked region. _W contains the number of
// particles allowed by an oversampled mask at each grid location.
PetscPrintf(PETSC_COMM_WORLD, "%f grid particles accumulated....\n", nrand);
// Now set the mask
// RS: For each cell, if the contents of _W exceed nthresh, set W = 1.
// Use dg1 and dg2 as wrappers to index the copies of _W and W.
int lo, hi;
dg1.slab(lo, hi);
dg1.Pull(_W); dg2.Pull(W);
for (int ix=lo; ix < hi; ++ix)
for (int iy=0; iy < N; ++iy)
for (int iz=0; iz < N; ++iz)
if (dg1(ix, iy,iz) > nthresh) {
dg2(ix, iy,iz) = 1.0;
} else {
dg1(ix, iy, iz) = 0.0; // Good to explicitly set this to zero as well
}
dg1.Push(_W, INSERT_VALUES, false);
dg2.Push(W, INSERT_VALUES, false);
double tmp;
VecSum(W, &tmp);
PetscPrintf(PETSC_COMM_WORLD,"Nonzero grid points in W : %f\n",tmp);
VecSum(_W, &nrand);
PetscPrintf(PETSC_COMM_WORLD,"Sum of background density vector : %f\n",nrand);
}
void BuildDensityGrid(int N, double L, Mask3D& mask, Particle& pp, int nover, double thresh, Vec& delta, Vec& W, double smooth) {
/* Parameters :
* INPUT ---
* N : grid size
* L : box size
* mask : A 3D positive mask (assumed to be 1 or 0)
* nover : Oversampling rate for defining the mean density (we use the GridInitialize routine)
* This determines the displacement.
* For a periodic box, nover means there will be nover**3 particles per grid.
* thresh: Fractional threshold below which to remove grid point from survey
* smooth: This is an optional parameter -- if set to > 0, it will smooth the density and mask
* fields before computing the overdensity.
* OUTPUT ---
* delta : What do think this is???
* W : Window function, 1 in survey, 0 elsewhere.
* Note that the output vectors are not cleared, so you had better make sure you don't leak memory.
*/
// Allocate two density grids
DensityGrid dg1(N,L), dg2(N,L);
delta = dg1.Allocate();
W = dg2.Allocate();
// First the particles
pp.TrimMask(mask);
pp.SlabDecompose(dg1);
dg2.CIC(delta,pp, false);
PetscPrintf(PETSC_COMM_WORLD, "Particles assigned to the grid.....\n");
// Now do the randoms
double nrand=0.0, nexp, nthresh;
nexp = pow((double) nover, 3);
nthresh = nexp*thresh;
{
double tmp = 1./nover, dx, dy, dz;
VecSet(W, 0.0); // Manually set to zero
Vec W1; VecDuplicate(W, &W1);
for (int ix = 0; ix < nover; ++ix) {
PetscPrintf(PETSC_COMM_WORLD,"Starting random loop %i of %i....\n",ix,nover-1);
dx = ix*tmp + tmp/2.0;
for (int iy = 0; iy < nover; ++iy) {
dy = iy*tmp + tmp/2.0;
for (int iz = 0; iz < nover; ++iz) {
dz = iz*tmp + tmp/2.0;
Particle rr; // Definition here is important, since it ensures destruction, before recreating
rr.GridInitialize(N, dx, dy, dz, L);
rr.TrimMask(mask); nrand += rr.npart;
// rr.SlabDecompose(dg2); We don't need to slab decompose because nproc divides N by construction
dg2.CIC(W1, rr, false); // No overdensity
VecAXPY(W, 1.0, W1);
}
}
}
}
PetscPrintf(PETSC_COMM_WORLD, "%f grid particles accumulated....\n", nrand);
PetscPrintf(PETSC_COMM_WORLD, "Expected number of particles=%f, threshold=%f\n", nexp, nthresh);
// Smooth if desired
if (smooth > 1.e-5) {
dg1.GaussSmooth(delta, smooth);
dg2.GaussSmooth(W, smooth);
}
// Now build up delta
int lo, hi;
nrand /= pp.npart;
dg1.slab(lo, hi);
dg1.Pull(delta); dg2.Pull(W);
for (int ix=lo; ix < hi; ++ix)
for (int iy=0; iy < N; ++iy)
for (int iz=0; iz < N; ++iz) {
if (dg2(ix, iy,iz) > nthresh) {
dg1(ix, iy,iz) = (dg1(ix,iy,iz)/dg2(ix, iy, iz)) * nrand - 1.0;
dg2(ix, iy,iz) = 1.0;
} else {
dg1(ix, iy, iz) = 0.0;
dg2(ix, iy, iz) = 0.0;
}
}
dg1.Push(delta, INSERT_VALUES, false);
dg2.Push(W, INSERT_VALUES, false);
VecSum(W, &nrand);
PetscPrintf(PETSC_COMM_WORLD,"Nonzero grid points in W : %f\n",nrand);
}
