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mfem/tests/unit/fem/test_getderivative.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 "unit_tests.hpp"
#include "mfem.hpp"
using namespace mfem;
namespace test_GetDerivative_parallel
{
double func(const Vector &coord)
{
if (coord.Size() == 1) { return std::sin(coord(0)); }
if (coord.Size() == 2) { return std::sin(coord(0)*coord(1)); }
return std::sin(coord(0)*coord(1)*coord(2));
}
#ifdef MFEM_USE_MPI
// Compares serial vs parallel result of GetDerivative.
TEST_CASE("GetDerivative", "[Parallel]")
{
for (int dimension = 1; dimension <= 3; ++dimension)
{
int num_procs;
MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
int myid;
MPI_Comm_rank(MPI_COMM_WORLD, &myid);
Mesh mesh;
if (dimension == 1)
{
mesh = Mesh::MakeCartesian1D(100, 1.0);
}
else if (dimension == 2)
{
mesh = Mesh::LoadFromFile("../../data/star-mixed-p2.mesh");
}
else
{
mesh = Mesh::LoadFromFile("../../data/fichera-mixed-p2.mesh");
}
for (int i = 0; i < 2; i++) { mesh.UniformRefinement(); }
ParMesh pmesh(MPI_COMM_WORLD, mesh);
FunctionCoefficient x_coeff(func);
H1_FECollection fec(3, dimension);
// Serial.
FiniteElementSpace fes(&mesh, &fec);
GridFunction gf(&fes), gf_grad(&fes);
gf.ProjectCoefficient(x_coeff);
// Parallel.
ParFiniteElementSpace pfes(&pmesh, &fec);
ParGridFunction pgf(&pfes), pgf_grad(&pfes);
pgf.ProjectCoefficient(x_coeff);
ConstantCoefficient zero(0.0);
for (int d = 0; d < dimension; d++)
{
gf.GetDerivative(1, d, gf_grad);
pgf.GetDerivative(1, d, pgf_grad);
REQUIRE(gf_grad.ComputeL2Error(zero) -
pgf_grad.ComputeL2Error(zero) == MFEM_Approx(0.0));
}
}
}
#endif
}