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/* Copyright 2019 Andrew Myers, Maxence Thevenet, Weiqun Zhang
*
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#include <WarpX.H>
#include <BilinearFilter.H>
#include <WarpX_f.H>
#ifdef _OPENMP
#include <omp.h>
#endif
using namespace amrex;
namespace {
void compute_stencil(Gpu::ManagedVector<Real> &stencil, int npass)
{
Gpu::ManagedVector<Real> old_s(1+npass,0.);
Gpu::ManagedVector<Real> new_s(1+npass,0.);
old_s[0] = 1.;
int jmax = 1;
amrex::Real loc;
// Convolve the filter with itself npass times
for(int ipass=1; ipass<npass+1; ipass++){
// element 0 has to be treated in its own way
new_s[0] = 0.5 * old_s[0];
if (1<jmax) new_s[0] += 0.5 * old_s[1];
loc = 0.;
// For each element j, apply the filter to
// old_s to get new_s[j]. loc stores the tmp
// filtered value.
for(int j=1; j<jmax+1; j++){
loc = 0.5 * old_s[j];
loc += 0.25 * old_s[j-1];
if (j<jmax) loc += 0.25 * old_s[j+1];
new_s[j] = loc;
}
// copy new_s into old_s
old_s = new_s;
// extend the stencil length for next iteration
jmax += 1;
}
// we use old_s here to make sure the stencil
// is corrent even when npass = 0
stencil = old_s;
stencil[0] *= 0.5; // because we will use it twice
}
}
void BilinearFilter::ComputeStencils(){
BL_PROFILE("BilinearFilter::ComputeStencils()");
stencil_length_each_dir = npass_each_dir;
stencil_length_each_dir += 1.;
#if (AMREX_SPACEDIM == 3)
// npass_each_dir = npass_x npass_y npass_z
stencil_x.resize( 1 + npass_each_dir[0] );
stencil_y.resize( 1 + npass_each_dir[1] );
stencil_z.resize( 1 + npass_each_dir[2] );
compute_stencil(stencil_x, npass_each_dir[0]);
compute_stencil(stencil_y, npass_each_dir[1]);
compute_stencil(stencil_z, npass_each_dir[2]);
#elif (AMREX_SPACEDIM == 2)
// npass_each_dir = npass_x npass_z
stencil_x.resize( 1 + npass_each_dir[0] );
stencil_z.resize( 1 + npass_each_dir[1] );
compute_stencil(stencil_x, npass_each_dir[0]);
compute_stencil(stencil_z, npass_each_dir[1]);
#endif
slen = stencil_length_each_dir.dim3();
#if (AMREX_SPACEDIM == 2)
slen.z = 1;
#endif
}
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