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mfem/fem/derefmat_op.cpp
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// Copyright (c) 2010-2025, Lawrence Livermore National Security, LLC. Produced
// at the Lawrence Livermore National Laboratory. All Rights reserved. See files
// LICENSE and NOTICE for details. LLNL-CODE-806117.
//
// This file is part of the MFEM library. For more information and source code
// availability visit https://mfem.org.
//
// MFEM is free software; you can redistribute it and/or modify it under the
// terms of the BSD-3 license. We welcome feedback and contributions, see file
// CONTRIBUTING.md for details.
#include "derefmat_op.hpp"
#include "fes_kernels.hpp"
/// \cond DO_NOT_DOCUMENT
namespace mfem
{
namespace internal
{
template <Ordering::Type Order, bool Atomic>
static void DerefMultKernelImpl(const DerefineMatrixOp &op, const Vector &x,
Vector &y)
{
DerefineMatrixOpMultFunctor<Order, Atomic> func;
func.xptr = x.Read();
y.UseDevice();
y = 0.;
func.yptr = y.ReadWrite();
func.bsptr = op.block_storage.Read();
func.boptr = op.block_offsets.Read();
func.brptr = op.block_row_idcs_offsets.Read();
func.bcptr = op.block_col_idcs_offsets.Read();
func.rptr = op.row_idcs.Read();
func.cptr = op.col_idcs.Read();
func.vdims = op.fespace->GetVDim();
func.nblocks = op.block_offsets.Size();
func.width = op.Width() / func.vdims;
func.height = op.Height() / func.vdims;
func.Run(op.max_rows);
}
} // namespace internal
DerefineMatrixOp::DerefineMatrixOp(FiniteElementSpace &fespace_, int old_ndofs,
const Table *old_elem_dof,
const Table *old_elem_fos)
: Operator(fespace_.GetVSize(), old_ndofs * fespace_.GetVDim()),
fespace(&fespace_)
{
static Kernels kernels;
constexpr int max_team_size = 256;
/// TODO: Implement DofTransformation support
MFEM_VERIFY(fespace->Nonconforming(),
"Not implemented for conforming meshes.");
MFEM_VERIFY(old_ndofs, "Missing previous (finer) space.");
MFEM_VERIFY(fespace->GetNDofs() <= old_ndofs,
"Previous space is not finer.");
const CoarseFineTransformations &dtrans =
fespace->GetMesh()->ncmesh->GetDerefinementTransforms();
MFEM_ASSERT(dtrans.embeddings.Size() == old_elem_dof->Size(), "");
const bool is_dg = fespace->FEColl()->GetContType()
== FiniteElementCollection::DISCONTINUOUS;
DenseMatrix localRVO; // for variable-order only
DenseTensor localR[Geometry::NumGeom];
int total_rows = 0;
int total_cols = 0;
block_offsets.SetSize(dtrans.embeddings.Size());
block_offsets.HostWrite();
if (fespace->IsVariableOrder())
{
// TODO: any potential for some compression here?
// determine storage size and offsets
block_offsets[0] = 0;
int total_size = 0;
for (int k = 0; k < dtrans.embeddings.Size(); ++k)
{
const Embedding &emb = dtrans.embeddings[k];
const FiniteElement *fe = fespace->GetFE(emb.parent);
const int ldof = fe->GetDof();
if (k + 1 < dtrans.embeddings.Size())
{
block_offsets[k + 1] = block_offsets[k] + ldof * ldof;
}
total_rows += ldof;
total_cols += ldof;
total_size += ldof * ldof;
}
block_storage.SetSize(total_size);
}
else
{
// compression scheme:
// block_offsets is the start of each block, potentially repeated
// only need to store localR for used shapes
Mesh::GeometryList elem_geoms(*fespace->GetMesh());
int geom_offsets[Geometry::NumGeom];
{
int size = 0;
for (int i = 0; i < elem_geoms.Size(); ++i)
{
fespace->GetLocalDerefinementMatrices(elem_geoms[i],
localR[elem_geoms[i]]);
geom_offsets[elem_geoms[i]] = size;
size += localR[elem_geoms[i]].TotalSize();
}
block_storage.SetSize(size);
// copy blocks into block_storage
auto bs_ptr = block_storage.HostWrite();
for (int i = 0; i < elem_geoms.Size(); ++i)
{
std::copy(localR[elem_geoms[i]].Data(),
localR[elem_geoms[i]].Data()
+ localR[elem_geoms[i]].TotalSize(),
bs_ptr);
bs_ptr += localR[elem_geoms[i]].TotalSize();
}
}
for (int k = 0; k < dtrans.embeddings.Size(); ++k)
{
const Embedding &emb = dtrans.embeddings[k];
Geometry::Type geom =
fespace->GetMesh()->GetElementBaseGeometry(emb.parent);
auto size = localR[geom].SizeI() * localR[geom].SizeJ();
total_rows += localR[geom].SizeI();
total_cols += localR[geom].SizeJ();
// set block offsets and sizes
block_offsets[k] = geom_offsets[geom] + size * emb.matrix;
}
}
row_idcs.SetSize(total_rows);
row_idcs.HostWrite();
col_idcs.SetSize(total_cols);
col_idcs.HostWrite();
block_row_idcs_offsets.SetSize(dtrans.embeddings.Size() + 1);
block_row_idcs_offsets.HostWrite();
block_col_idcs_offsets.SetSize(dtrans.embeddings.Size() + 1);
block_col_idcs_offsets.HostWrite();
block_row_idcs_offsets[0] = 0;
block_col_idcs_offsets[0] = 0;
// compute index information
Array<int> dofs, old_dofs;
max_rows = 1;
{
Array<int> mark(fespace->GetNDofs());
mark = 0;
auto bs_ptr = block_storage.HostWrite();
int ridx = 0;
int cidx = 0;
int num_marked = 0;
for (int k = 0; k < dtrans.embeddings.Size(); k++)
{
const Embedding &emb = dtrans.embeddings[k];
Geometry::Type geom =
fespace->GetMesh()->GetElementBaseGeometry(emb.parent);
if (fespace->IsVariableOrder())
{
const FiniteElement *fe = fespace->GetFE(emb.parent);
const DenseTensor &pmats = dtrans.point_matrices[geom];
const int ldof = fe->GetDof();
IsoparametricTransformation isotr;
isotr.SetIdentityTransformation(geom);
localRVO.SetSize(ldof, ldof);
isotr.SetPointMat(pmats(emb.matrix));
// Local restriction is size ldofxldof assuming that the parent
// and child are of same polynomial order.
fe->GetLocalRestriction(isotr, localRVO);
// copy block
auto size = localRVO.Height() * localRVO.Width();
std::copy(localRVO.Data(), localRVO.Data() + size, bs_ptr);
bs_ptr += size;
}
DenseMatrix &lR =
fespace->IsVariableOrder() ? localRVO : localR[geom](emb.matrix);
block_row_idcs_offsets[k + 1] =
block_row_idcs_offsets[k] + lR.Height();
block_col_idcs_offsets[k + 1] = block_col_idcs_offsets[k] + lR.Width();
max_rows = std::max(lR.Height(), max_rows);
// index information
fespace->elem_dof->GetRow(emb.parent, dofs);
old_elem_dof->GetRow(k, old_dofs);
MFEM_VERIFY(old_dofs.Size() == dofs.Size(),
"Parent and child must have same #dofs.");
for (int i = 0; i < lR.Height(); ++i, ++ridx)
{
if (!std::isfinite(lR(i, 0)))
{
row_idcs[ridx] = INT_MAX;
continue;
}
int r = dofs[i];
int m = (r >= 0) ? r : (-1 - r);
if (is_dg || !mark[m])
{
row_idcs[ridx] = r;
mark[m] = 1;
++num_marked;
}
else
{
row_idcs[ridx] = INT_MAX;
}
}
for (int i = 0; i < lR.Width(); ++i, ++cidx)
{
col_idcs[cidx] = old_dofs[i];
}
}
if (!is_dg && !fespace->IsVariableOrder())
{
MFEM_VERIFY(num_marked * fespace->GetVDim() == Height(),
"internal error: not all rows were set.");
}
}
// if not using GPU, set max_rows/max_cols to zero
if (Device::Allows(Backend::DEVICE_MASK))
{
max_rows = std::min(max_rows, max_team_size);
}
else
{
max_rows = 1;
}
}
void DerefineMatrixOp::Mult(const Vector &x, Vector &y) const
{
const bool is_dg = fespace->FEColl()->GetContType()
== FiniteElementCollection::DISCONTINUOUS;
// DG needs atomic summation
MultKernel::Run(fespace->GetOrdering(), is_dg, *this, x, y);
}
DerefineMatrixOp::Kernels::Kernels()
{
MultKernel::Specialization<Ordering::byNODES, false>::Add();
MultKernel::Specialization<Ordering::byVDIM, false>::Add();
MultKernel::Specialization<Ordering::byNODES, true>::Add();
MultKernel::Specialization<Ordering::byVDIM, true>::Add();
}
template <Ordering::Type Order, bool Atomic>
DerefineMatrixOp::MultKernelType DerefineMatrixOp::MultKernel::Kernel()
{
return internal::DerefMultKernelImpl<Order, Atomic>;
}
DerefineMatrixOp::MultKernelType
DerefineMatrixOp::MultKernel::Fallback(Ordering::Type, bool)
{
MFEM_ABORT("invalid MultKernel parameters");
}
} // namespace mfem
/// \endcond DO_NOT_DOCUMENT