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SERiF/src/poly/utils/private/integrators.cpp

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/* ***********************************************************************
//
// Copyright (C) 2025 -- The 4D-STAR Collaboration
// File Author: Emily Boudreaux
// Last Modified: April 21, 2025
//
// 4DSSE is free software; you can use it and/or modify
// it under the terms and restrictions the GNU General Library Public
// License version 3 (GPLv3) as published by the Free Software Foundation.
//
// 4DSSE is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with this software; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// *********************************************************************** */
#include "mfem.hpp"
#include <cmath>
#include "integrators.h"
namespace polyMFEMUtils {
NonlinearPowerIntegrator::NonlinearPowerIntegrator(const double n) :
m_polytropicIndex(n) {}
void NonlinearPowerIntegrator::AssembleElementVector(
const mfem::FiniteElement &el,
mfem::ElementTransformation &Trans,
const mfem::Vector &elfun,
mfem::Vector &elvect) {
const mfem::IntegrationRule *ir = &mfem::IntRules.Get(el.GetGeomType(), 2 * el.GetOrder() + 3);
int dof = el.GetDof();
elvect.SetSize(dof);
elvect = 0.0;
mfem::Vector shape(dof);
for (int iqp = 0; iqp < ir->GetNPoints(); iqp++) {
mfem::IntegrationPoint ip = ir->IntPoint(iqp);
Trans.SetIntPoint(&ip);
double weight = ip.weight * Trans.Weight();
el.CalcShape(ip, shape);
double u_val = 0.0;
for (int j = 0; j < dof; j++) {
u_val += elfun(j) * shape(j);
}
double u_safe = std::max(u_val, 0.0);
double u_nl = std::pow(u_safe, m_polytropicIndex);
double x2_u_nl = u_nl;
for (int i = 0; i < dof; i++){
elvect(i) += shape(i) * x2_u_nl * weight;
}
}
}
void NonlinearPowerIntegrator::AssembleElementGrad (
const mfem::FiniteElement &el,
mfem::ElementTransformation &Trans,
const mfem::Vector &elfun,
mfem::DenseMatrix &elmat) {
const mfem::IntegrationRule *ir = &mfem::IntRules.Get(el.GetGeomType(), 2 * el.GetOrder() + 3);
int dof = el.GetDof();
elmat.SetSize(dof);
elmat = 0.0;
mfem::Vector shape(dof);
for (int iqp = 0; iqp < ir->GetNPoints(); iqp++) {
const mfem::IntegrationPoint &ip = ir->IntPoint(iqp);
Trans.SetIntPoint(&ip);
double weight = ip.weight * Trans.Weight();
el.CalcShape(ip, shape);
double u_val = 0.0;
for (int j = 0; j < dof; j++) {
u_val += elfun(j) * shape(j);
}
// Calculate the Jacobian
double u_safe = std::max(u_val, 0.0);
double d_u_nl = m_polytropicIndex * std::pow(u_safe, m_polytropicIndex - 1);
double x2_d_u_nl = d_u_nl;
for (int i = 0; i < dof; i++) {
for (int j = 0; j < dof; j++) {
elmat(i, j) += shape(i) * x2_d_u_nl * shape(j) * weight;
}
}
}
}
} // namespace polyMFEMUtils