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SERiF/src/poly/solver/private/polySolver.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 "polySolver.h"
#include <memory>
#include <stdexcept>
#include <string>
#include <utility>
#include "mfem.hpp"
#include "4DSTARTypes.h"
#include "config.h"
#include "integrators.h"
#include "mfem.hpp"
#include "operator.h"
#include "polyCoeff.h"
#include "probe.h"
#include "resourceManager.h"
#include "resourceManagerTypes.h"
#include "quill/LogMacros.h"
namespace laneEmden {
double a (const int k, const double n) { // NOLINT(*-no-recursion)
if ( k == 0 ) { return 1; }
if ( k == 1 ) { return 0; }
else { return -(c(k-2, n)/(std::pow(k, 2)+k)); }
}
double c(const int m, const double n) { // NOLINT(*-no-recursion)
if ( m == 0 ) { return std::pow(a(0, n), n); }
else {
double termOne = 1.0/(m*a(0, n));
double acc = 0;
for (int k = 1; k <= m; k++) {
acc += (k*n-m+k)*a(k, n)*c(m-k, n);
}
return termOne*acc;
}
}
double thetaSeriesExpansion(const double xi, const double n, const int order) {
double acc = 0;
for (int k = 0; k < order; k++) {
acc += a(k, n) * std::pow(xi, k);
}
return acc;
}
}
PolySolver::PolySolver(mfem::Mesh& mesh, const double n, const double order)
: m_config(Config::getInstance()),
m_logManager(Probe::LogManager::getInstance()),
m_logger(m_logManager.getLogger("log")),
m_polytropicIndex(n),
m_feOrder(order),
m_mesh(mesh) {
// Use feOrder - 1 for the RT space to satisfy Brezzi-Babuska condition
// for the H1 and RT [H(div)] spaces
m_fecH1 = std::make_unique<mfem::H1_FECollection>(m_feOrder, m_mesh.SpaceDimension());
m_fecRT = std::make_unique<mfem::RT_FECollection>(m_feOrder - 1, m_mesh.SpaceDimension());
m_feTheta = std::make_unique<mfem::FiniteElementSpace>(&m_mesh, m_fecH1.get());
m_fePhi = std::make_unique<mfem::FiniteElementSpace>(&m_mesh, m_fecRT.get());
m_theta = std::make_unique<mfem::GridFunction>(m_feTheta.get());
m_phi = std::make_unique<mfem::GridFunction>(m_fePhi.get());
assembleBlockSystem();
}
PolySolver::PolySolver(const double n, const double order)
: PolySolver(prepareMesh(n), n, order){}
mfem::Mesh& PolySolver::prepareMesh(const double n) {
if (n > 4.99 || n < 0.0) {
throw std::runtime_error("The polytropic index n must be less than 5.0 and greater than 0.0. Currently it is " + std::to_string(n));
}
const ResourceManager& rm = ResourceManager::getInstance();
const Resource& genericResource = rm.getResource("mesh:polySphere");
const auto &meshIO = std::get<std::unique_ptr<MeshIO>>(genericResource);
meshIO->LinearRescale(polycoeff::x1(n));
return meshIO->GetMesh();
}
PolySolver::~PolySolver() = default;
void PolySolver::assembleBlockSystem() {
mfem::Array<int> blockOffsets = computeBlockOffsets();
const std::unique_ptr<formBundle> forms = buildIndividualForms(blockOffsets);
// --- Build the BlockOperator ---
m_polytropOperator = std::make_unique<PolytropeOperator>(
std::move(forms->M),
std::move(forms->Q),
std::move(forms->D),
std::move(forms->f),
blockOffsets,
m_polytropicIndex);
}
mfem::Array<int> PolySolver::computeBlockOffsets() const {
mfem::Array<int> blockOffsets;
blockOffsets.SetSize(3);
blockOffsets[0] = 0;
blockOffsets[1] = m_feTheta->GetVSize(); // Get actual number of dofs *before* applying BCs
blockOffsets[2] = m_fePhi->GetVSize();
blockOffsets.PartialSum(); // Cumulative sum to get the offsets
return blockOffsets;
}
std::unique_ptr<formBundle> PolySolver::buildIndividualForms(const mfem::Array<int> &blockOffsets) {
// --- Assemble the MixedBilinear and Bilinear forms (M, D, and Q) ---
auto forms = std::make_unique<formBundle>(
std::make_unique<mfem::MixedBilinearForm>(m_fePhi.get(), m_feTheta.get()),
std::make_unique<mfem::MixedBilinearForm>(m_feTheta.get(), m_fePhi.get()),
std::make_unique<mfem::BilinearForm>(m_fePhi.get()),
std::make_unique<mfem::NonlinearForm>(m_feTheta.get())
);
// --- -M negation -> M ---
mfem::Vector negOneVec(m_mesh.SpaceDimension());
negOneVec = -1.0;
m_negationCoeff = std::make_unique<mfem::VectorConstantCoefficient>(negOneVec);
// --- Add the integrators to the forms ---
forms->M->AddDomainIntegrator(new mfem::MixedVectorWeakDivergenceIntegrator(*m_negationCoeff));
forms->Q->AddDomainIntegrator(new mfem::MixedVectorGradientIntegrator());
forms->D->AddDomainIntegrator(new mfem::VectorFEMassIntegrator());
// --- Assemble and Finalize the forms ---
assembleAndFinalizeForm(forms->M);
assembleAndFinalizeForm(forms->Q);
assembleAndFinalizeForm(forms->D);
forms->f->AddDomainIntegrator(new polyMFEMUtils::NonlinearPowerIntegrator(m_polytropicIndex));
return forms;
}
void PolySolver::assembleAndFinalizeForm(auto &f) {
// This constructs / ensures the matrix representation for each form
// Assemble => Computes the local element matrices across the domain. Adds these to the global matrix . Adds these to the global matrix.
// Finalize => Builds the sparsity pattern and allows the SparseMatrix representation to be extracted.
f->Assemble();
f->Finalize();
}
void PolySolver::solve() const {
// --- Set the initial guess for the solution ---
setInitialGuess();
setOperatorEssentialTrueDofs();
const auto thetaVec = static_cast<mfem::Vector>(*m_theta); // NOLINT(*-slicing)
const auto phiVec = static_cast<mfem::Vector>(*m_phi); // NOLINT(*-slicing)
// --- Finalize the operator ---
// Finalize with the initial state of theta for the initial jacobian calculation
m_polytropOperator->finalize(thetaVec);
// It's safer to get the offsets directly from the operator after finalization
const mfem::Array<int>& block_offsets = m_polytropOperator->GetBlockOffsets(); // Assuming a getter exists or accessing member if public/friend
mfem::BlockVector state_vector(block_offsets);
state_vector.GetBlock(0) = thetaVec; // NOLINT(*-slicing)
state_vector.GetBlock(1) = phiVec; // NOLINT(*-slicing)
mfem::Vector zero_rhs(block_offsets.Last());
zero_rhs = 0.0;
const solverBundle sb = setupNewtonSolver();
sb.newton.Mult(zero_rhs, state_vector);
// --- Save and view an approximate 1D solution ---
saveAndViewSolution(state_vector);
}
SSE::MFEMArrayPairSet PolySolver::getEssentialTrueDof() const {
mfem::Array<int> theta_ess_tdof_list;
mfem::Array<int> phi_ess_tdof_list;
mfem::Array<int> thetaCenterDofs, phiCenterDofs; // phiCenterDofs are not used
mfem::Array<double> thetaCenterVals;
std::tie(thetaCenterDofs, phiCenterDofs) = findCenterElement();
thetaCenterVals.SetSize(thetaCenterDofs.Size());
thetaCenterVals = 1.0;
mfem::Array<int> ess_brd(m_mesh.bdr_attributes.Max());
ess_brd = 1;
mfem::Array<double> thetaSurfaceVals, phiSurfaceVals;
m_feTheta->GetEssentialTrueDofs(ess_brd, theta_ess_tdof_list);
m_fePhi->GetEssentialTrueDofs(ess_brd, phi_ess_tdof_list);
thetaSurfaceVals.SetSize(theta_ess_tdof_list.Size());
thetaSurfaceVals = 0.0;
phiSurfaceVals.SetSize(phi_ess_tdof_list.Size());
phiSurfaceVals = polycoeff::thetaSurfaceFlux(m_polytropicIndex);
// combine the essential dofs with the center dofs
theta_ess_tdof_list.Append(thetaCenterDofs);
thetaSurfaceVals.Append(thetaCenterVals);
SSE::MFEMArrayPair thetaPair = std::make_pair(theta_ess_tdof_list, thetaSurfaceVals);
SSE::MFEMArrayPair phiPair = std::make_pair(phi_ess_tdof_list, phiSurfaceVals);
SSE::MFEMArrayPairSet pairSet = std::make_pair(thetaPair, phiPair);
return pairSet;
}
std::pair<mfem::Array<int>, mfem::Array<int>> PolySolver::findCenterElement() const {
mfem::Array<int> thetaCenterDofs;
mfem::Array<int> phiCenterDofs;
mfem::DenseMatrix centerPoint(m_mesh.SpaceDimension(), 1);
centerPoint(0, 0) = 0.0;
centerPoint(1, 0) = 0.0;
centerPoint(2, 0) = 0.0;
mfem::Array<int> elementIDs;
mfem::Array<mfem::IntegrationPoint> ips;
m_mesh.FindPoints(centerPoint, elementIDs, ips);
mfem::Array<int> tempDofs;
for (int i = 0; i < elementIDs.Size(); i++) {
m_feTheta->GetElementDofs(elementIDs[i], tempDofs);
thetaCenterDofs.Append(tempDofs);
m_fePhi->GetElementDofs(elementIDs[i], tempDofs);
phiCenterDofs.Append(tempDofs);
}
return std::make_pair(thetaCenterDofs, phiCenterDofs);
}
void PolySolver::setInitialGuess() const {
// --- Set the initial guess for the solution ---
mfem::FunctionCoefficient thetaInitGuess (
[this](const mfem::Vector &x) {
const double r = x.Norml2();
// const double radius = Probe::getMeshRadius(*m_mesh);
// const double u = 1/radius;
// return (-1.0/radius) * r + 1;
// return -std::pow((u*r), 2)+1.0; // The series expansion is a better guess; however, this is cheaper and ensures that the value at the surface is very close to zero in a way that the series expansion does not
return laneEmden::thetaSeriesExpansion(r, m_polytropicIndex, 10);
}
);
mfem::VectorFunctionCoefficient phiSurfaceVectors (m_mesh.SpaceDimension(),
[this](const mfem::Vector &x, mfem::Vector &y) {
const double r = x.Norml2();
mfem::Vector xh(x);
xh /= r; // Normalize the vector
y.SetSize(m_mesh.SpaceDimension());
y = xh;
y *= polycoeff::thetaSurfaceFlux(m_polytropicIndex);
}
);
// We want to apply specific boundary conditions to the surface
mfem::Array<int> ess_brd(m_mesh.bdr_attributes.Max());
ess_brd = 1;
// θ = 0 at surface
mfem::ConstantCoefficient surfacePotential(0);
m_theta->ProjectCoefficient(thetaInitGuess);
m_theta->ProjectBdrCoefficient(surfacePotential, ess_brd);
mfem::GradientGridFunctionCoefficient phiInitGuess (m_theta.get());
m_phi->ProjectCoefficient(phiInitGuess);
// Note that this will not result in perfect boundary conditions
// because it must maintain H(div) continuity, this is
// why inhomogenous boundary conditions enforcement is needed for φ
// This manifests in PolytropeOperator::Mult where we do not
// just zero out the essential dof elements in the residuals vector
// for φ; rather, we need to set this to something which will push the
// solver towards a more consistent answer (x_φ - target)
m_phi->ProjectBdrCoefficientNormal(phiSurfaceVectors, ess_brd);
if (m_config.get<bool>("Poly:Solver:ViewInitialGuess", false)) {
Probe::glVisView(*m_theta, m_mesh, "θ init");
Probe::glVisView(*m_phi, m_mesh, "φ init");
}
}
void PolySolver::saveAndViewSolution(const mfem::BlockVector& state_vector) const {
mfem::BlockVector x_block(const_cast<mfem::BlockVector&>(state_vector), m_polytropOperator->GetBlockOffsets());
mfem::Vector& x_theta = x_block.GetBlock(0);
mfem::Vector& x_phi = x_block.GetBlock(1);
if (m_config.get<bool>("Poly:Output:View", false)) {
Probe::glVisView(x_theta, *m_feTheta, "θ Solution");
Probe::glVisView(x_phi, *m_fePhi, "ɸ Solution");
}
// --- Extract the Solution ---
if (m_config.get<bool>("Poly:Output:1D:Save", true)) {
const auto solutionPath = m_config.get<std::string>("Poly:Output:1D:Path", "polytropeSolution_1D.csv");
auto derivSolPath = "d" + solutionPath;
const auto rayCoLatitude = m_config.get<double>("Poly:Output:1D:RayCoLatitude", 0.0);
const auto rayLongitude = m_config.get<double>("Poly:Output:1D:RayLongitude", 0.0);
const auto raySamples = m_config.get<int>("Poly:Output:1D:RaySamples", 100);
const std::vector rayDirection = {rayCoLatitude, rayLongitude};
Probe::getRaySolution(x_theta, *m_feTheta, rayDirection, raySamples, solutionPath);
// Probe::getRaySolution(x_phi, *m_fePhi, rayDirection, raySamples, derivSolPath);
}
}
void PolySolver::setOperatorEssentialTrueDofs() const {
const SSE::MFEMArrayPairSet ess_tdof_pair_set = getEssentialTrueDof();
m_polytropOperator->SetEssentialTrueDofs(ess_tdof_pair_set);
}
void PolySolver::LoadSolverUserParams(double &newtonRelTol, double &newtonAbsTol, int &newtonMaxIter, int &newtonPrintLevel, double &gmresRelTol, double &gmresAbsTol, int &gmresMaxIter, int &gmresPrintLevel) const {
newtonRelTol = m_config.get<double>("Poly:Solver:Newton:RelTol", 1e-7);
newtonAbsTol = m_config.get<double>("Poly:Solver:Newton:AbsTol", 1e-7);
newtonMaxIter = m_config.get<int>("Poly:Solver:Newton:MaxIter", 200);
newtonPrintLevel = m_config.get<int>("Poly:Solver:Newton:PrintLevel", 1);
gmresRelTol = m_config.get<double>("Poly:Solver:GMRES:RelTol", 1e-10);
gmresAbsTol = m_config.get<double>("Poly:Solver:GMRES:AbsTol", 1e-12);
gmresMaxIter = m_config.get<int>("Poly:Solver:GMRES:MaxIter", 2000);
gmresPrintLevel = m_config.get<int>("Poly:Solver:GMRES:PrintLevel", 0);
LOG_DEBUG(m_logger, "Newton Solver (relTol: {:0.2E}, absTol: {:0.2E}, maxIter: {}, printLevel: {})", newtonRelTol, newtonAbsTol, newtonMaxIter, newtonPrintLevel);
LOG_DEBUG(m_logger, "GMRES Solver (relTol: {:0.2E}, absTol: {:0.2E}, maxIter: {}, printLevel: {})", gmresRelTol, gmresAbsTol, gmresMaxIter, gmresPrintLevel);
}
void PolySolver::GetDofCoordinates(const mfem::FiniteElementSpace &fes, const std::string& filename) {
mfem::Mesh *mesh = fes.GetMesh();
double r = Probe::getMeshRadius(*mesh);
std::ofstream outputFile(filename, std::ios::out | std::ios::trunc);
outputFile << "dof,R,r,x,y,z" << '\n';
const int nElements = mesh->GetNE();
mfem::Vector coords;
mfem::IntegrationPoint ipZero;
double p[3] = {0.0, 0.0, 0.0};
int actual_idx;
ipZero.Set3(p);
for (int i = 0; i < nElements; i++) {
mfem::Array<int> elemDofs;
fes.GetElementDofs(i, elemDofs);
mfem::ElementTransformation* T = mesh->GetElementTransformation(i);
mfem::Vector physCoord(3);
T->Transform(ipZero, physCoord);
for (int dofID = 0; dofID < elemDofs.Size(); dofID++) {
if (elemDofs[dofID] < 0) {
actual_idx = -elemDofs[dofID] - 1;
} else {
actual_idx = elemDofs[dofID];
}
outputFile << actual_idx;
if (dofID != elemDofs.Size() - 1) {
outputFile << "|";
} else {
outputFile << ",";
}
}
outputFile << r << "," << physCoord.Norml2() << "," << physCoord[0] << "," << physCoord[1] << "," << physCoord[2] << '\n';
}
outputFile.close();
}
solverBundle PolySolver::setupNewtonSolver() const {
// --- Load configuration parameters ---
double newtonRelTol, newtonAbsTol, gmresRelTol, gmresAbsTol;
int newtonMaxIter, newtonPrintLevel, gmresMaxIter, gmresPrintLevel;
LoadSolverUserParams(newtonRelTol, newtonAbsTol, newtonMaxIter, newtonPrintLevel, gmresRelTol, gmresAbsTol,
gmresMaxIter, gmresPrintLevel);
solverBundle solver; // Use this solver bundle to ensure lifetime safety
solver.solver.SetRelTol(gmresRelTol);
solver.solver.SetAbsTol(gmresAbsTol);
solver.solver.SetMaxIter(gmresMaxIter);
solver.solver.SetPrintLevel(gmresPrintLevel);
// solver.solver.SetPreconditioner(m_polytropOperator->GetPreconditioner());
// --- Set up the Newton solver ---
solver.newton.SetRelTol(newtonRelTol);
solver.newton.SetAbsTol(newtonAbsTol);
solver.newton.SetMaxIter(newtonMaxIter);
solver.newton.SetPrintLevel(newtonPrintLevel);
solver.newton.SetOperator(*m_polytropOperator);
// --- Created the linear solver which is used to invert the jacobian ---
solver.newton.SetSolver(solver.solver);
return solver;
}