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mfem/fem/ceed/interface/mixed_integrator.hpp
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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.
#ifndef MFEM_LIBCEED_MIXED_INTEGRATOR
#define MFEM_LIBCEED_MIXED_INTEGRATOR
#include "ceed.hpp"
#include "integrator.hpp"
#include <unordered_map>
namespace mfem
{
namespace ceed
{
/** @brief This class wraps a `ceed::PAIntegrator` or `ceed::MFIntegrator` to
support mixed finite element spaces. */
template <typename CeedInteg>
class MixedIntegrator : public ceed::Operator
{
#ifdef MFEM_USE_CEED
using ElementKey = std::pair<int, int>; //< Element::Type, Order >
struct key_hash
{
std::size_t operator()(const ElementKey& k) const
{
return k.first + 2 * k.second;
}
};
using ElementsMap = std::unordered_map<const ElementKey, int*, key_hash>;
std::vector<CeedInteg*> sub_ops;
public:
template <typename Integrator, typename CeedOperatorInfo, typename CoeffType>
void Assemble(const Integrator &integ,
CeedOperatorInfo &info,
const mfem::FiniteElementSpace &fes,
CoeffType *Q)
{
ElementsMap count;
ElementsMap element_indices;
ElementsMap offsets;
// Count the number of elements of each type
for (int i = 0; i < fes.GetNE(); i++)
{
ElementKey key(fes.GetElementType(i), fes.GetElementOrder(i));
auto value = count.find(key);
if (value == count.end())
{
count[key] = new int(1);
}
else
{
(*value->second)++;
}
}
// Initialization of the arrays
for ( const auto& value : count )
{
element_indices[value.first] = new int[*value.second];
offsets[value.first] = new int(0);
}
// Populates the indices arrays for each element type
for (int i = 0; i < fes.GetNE(); i++)
{
ElementKey key(fes.GetElementType(i), fes.GetElementOrder(i));
int &offset = *(offsets[key]);
int* indices_array = element_indices[key];
indices_array[offset] = i;
offset++;
}
// Create composite CeedOperator
CeedOperatorCreateComposite(internal::ceed, &oper);
// Create each sub-CeedOperator
sub_ops.reserve(element_indices.size());
for (const auto& value : element_indices)
{
const int* indices = value.second;
const int first_index = indices[0];
const mfem::FiniteElement &el = *fes.GetFE(first_index);
auto &T = *fes.GetMesh()->GetElementTransformation(first_index);
MFEM_ASSERT(!integ.GetIntRule(),
"Mixed mesh integrators should not have an"
" IntegrationRule.");
const IntegrationRule &ir = GetRule(integ, el, el, T);
auto sub_op = new CeedInteg();
int nelem = *count[value.first];
sub_op->Assemble(info, fes, ir, nelem, indices, Q);
sub_ops.push_back(sub_op);
CeedOperatorCompositeAddSub(oper, sub_op->GetCeedOperator());
}
const int ndofs = fes.GetVDim() * fes.GetNDofs();
CeedVectorCreate(internal::ceed, ndofs, &u);
CeedVectorCreate(internal::ceed, ndofs, &v);
}
virtual ~MixedIntegrator()
{
for (auto sub_op : sub_ops)
{
delete sub_op;
}
}
#endif
};
} // namespace ceed
} // namespace mfem
#endif // MFEM_LIBCEED_MIXED_INTEGRATOR