384 lines
13 KiB
C++
384 lines
13 KiB
C++
// MFEM Example 1 - Parallel Version
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// PETSc Modification
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//
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// Compile with: make ex1p
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//
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// Sample runs: mpirun -np 4 ex1p -m ../../data/amr-quad.mesh
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// mpirun -np 4 ex1p -m ../../data/amr-quad.mesh --petscopts rc_ex1p
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//
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// Device sample runs:
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// mpirun -np 4 ex1p -pa -d cuda --petscopts rc_ex1p_device
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//
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// Description: This example code demonstrates the use of MFEM to define a
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// simple finite element discretization of the Poisson problem
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// -Delta u = 1 with homogeneous Dirichlet boundary conditions.
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// Specifically, we discretize using a FE space of the specified
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// order, or if order < 1 using an isoparametric/isogeometric
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// space (i.e. quadratic for quadratic curvilinear mesh, NURBS for
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// NURBS mesh, etc.)
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//
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// The example highlights the use of mesh refinement, finite
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// element grid functions, as well as linear and bilinear forms
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// corresponding to the left-hand side and right-hand side of the
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// discrete linear system. We also cover the explicit elimination
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// of essential boundary conditions, static condensation, and the
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// optional connection to the GLVis tool for visualization.
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// The example also shows how PETSc Krylov solvers can be used by
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// wrapping a HypreParMatrix (or not) and a Solver, together with
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// customization using an options file (see rc_ex1p) We also
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// provide an example on how to visualize the iterative solution
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// inside a PETSc solver.
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#include "mfem.hpp"
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#include <fstream>
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#include <iostream>
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#ifndef MFEM_USE_PETSC
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#error This example requires that MFEM is built with MFEM_USE_PETSC=YES
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#endif
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using namespace std;
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using namespace mfem;
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class UserMonitor : public PetscSolverMonitor
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{
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private:
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ParBilinearForm *a;
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ParLinearForm *b;
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public:
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UserMonitor(ParBilinearForm *a_, ParLinearForm *b_)
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: PetscSolverMonitor(true,false), a(a_), b(b_) {}
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void MonitorSolution(PetscInt it, PetscReal norm, const Vector &X)
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{
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// we plot the first 5 iterates
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if (!it || it > 5) { return; }
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ParFiniteElementSpace *fespace = a->ParFESpace();
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ParMesh *mesh = fespace->GetParMesh();
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ParGridFunction x(fespace);
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a->RecoverFEMSolution(X, *b, x);
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char vishost[] = "localhost";
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int visport = 19916;
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int num_procs, myid;
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MPI_Comm_size(mesh->GetComm(),&num_procs);
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MPI_Comm_rank(mesh->GetComm(),&myid);
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socketstream sol_sock(vishost, visport);
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sol_sock << "parallel " << num_procs << " " << myid << "\n";
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sol_sock.precision(8);
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sol_sock << "solution\n" << *mesh << x
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<< "window_title 'Iteration no " << it << "'" << flush;
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}
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};
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int main(int argc, char *argv[])
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{
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// 1. Initialize MPI and HYPRE.
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Mpi::Init(argc, argv);
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int num_procs = Mpi::WorldSize();
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int myid = Mpi::WorldRank();
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Hypre::Init();
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// 2. Parse command-line options.
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const char *mesh_file = "../../data/star.mesh";
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int order = 1;
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bool static_cond = false;
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bool pa = false;
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bool visualization = false;
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const char *device_config = "cpu";
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bool use_petsc = true;
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const char *petscrc_file = "";
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bool petscmonitor = false;
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bool forcewrap = false;
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bool useh2 = false;
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OptionsParser args(argc, argv);
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args.AddOption(&mesh_file, "-m", "--mesh",
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"Mesh file to use.");
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args.AddOption(&order, "-o", "--order",
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"Finite element order (polynomial degree) or -1 for"
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" isoparametric space.");
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args.AddOption(&static_cond, "-sc", "--static-condensation", "-no-sc",
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"--no-static-condensation", "Enable static condensation.");
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args.AddOption(&pa, "-pa", "--partial-assembly", "-no-pa",
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"--no-partial-assembly", "Enable Partial Assembly.");
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args.AddOption(&device_config, "-d", "--device",
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"Device configuration string, see Device::Configure().");
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args.AddOption(&visualization, "-vis", "--visualization", "-no-vis",
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"--no-visualization",
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"Enable or disable GLVis visualization.");
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args.AddOption(&use_petsc, "-usepetsc", "--usepetsc", "-no-petsc",
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"--no-petsc",
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"Use or not PETSc to solve the linear system.");
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args.AddOption(&petscrc_file, "-petscopts", "--petscopts",
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"PetscOptions file to use.");
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args.AddOption(&petscmonitor, "-petscmonitor", "--petscmonitor",
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"-no-petscmonitor", "--no-petscmonitor",
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"Enable or disable GLVis visualization of residual.");
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args.AddOption(&forcewrap, "-forcewrap", "--forcewrap",
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"-noforce-wrap", "--noforce-wrap",
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"Force matrix-free.");
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args.AddOption(&useh2, "-useh2", "--useh2", "-no-h2",
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"--no-h2",
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"Use or not the H2 matrix solver.");
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args.Parse();
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if (!args.Good())
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{
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if (myid == 0)
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{
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args.PrintUsage(cout);
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}
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return 1;
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}
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if (myid == 0)
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{
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args.PrintOptions(cout);
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}
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// 3. Enable hardware devices such as GPUs, and programming models such as
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// CUDA, OCCA, RAJA and OpenMP based on command line options.
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Device device(device_config);
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if (myid == 0) { device.Print(); }
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// 3b. We initialize PETSc
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MFEMInitializePetsc(NULL,NULL,petscrc_file,NULL);
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// 4. Read the (serial) mesh from the given mesh file on all processors. We
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// can handle triangular, quadrilateral, tetrahedral, hexahedral, surface
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// and volume meshes with the same code.
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Mesh *mesh = new Mesh(mesh_file, 1, 1);
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int dim = mesh->Dimension();
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// 5. Refine the serial mesh on all processors to increase the resolution. In
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// this example we do 'ref_levels' of uniform refinement. We choose
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// 'ref_levels' to be the largest number that gives a final mesh with no
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// more than 10,000 elements.
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{
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int ref_levels =
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(int)floor(log(10000./mesh->GetNE())/log(2.)/dim);
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for (int l = 0; l < ref_levels; l++)
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{
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mesh->UniformRefinement();
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}
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}
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// 6. Define a parallel mesh by a partitioning of the serial mesh. Refine
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// this mesh further in parallel to increase the resolution. Once the
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// parallel mesh is defined, the serial mesh can be deleted.
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ParMesh *pmesh = new ParMesh(MPI_COMM_WORLD, *mesh);
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delete mesh;
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{
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int par_ref_levels = 2;
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for (int l = 0; l < par_ref_levels; l++)
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{
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pmesh->UniformRefinement();
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}
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}
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// 7. Define a parallel finite element space on the parallel mesh. Here we
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// use continuous Lagrange finite elements of the specified order. If
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// order < 1, we instead use an isoparametric/isogeometric space.
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FiniteElementCollection *fec;
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bool delete_fec;
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if (order > 0)
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{
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fec = new H1_FECollection(order, dim);
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delete_fec = true;
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}
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else if (pmesh->GetNodes())
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{
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fec = pmesh->GetNodes()->OwnFEC();
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delete_fec = false;
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if (myid == 0)
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{
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cout << "Using isoparametric FEs: " << fec->Name() << endl;
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}
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}
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else
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{
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fec = new H1_FECollection(order = 1, dim);
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delete_fec = true;
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}
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ParFiniteElementSpace *fespace = new ParFiniteElementSpace(pmesh, fec);
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HYPRE_BigInt size = fespace->GlobalTrueVSize();
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if (myid == 0)
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{
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cout << "Number of finite element unknowns: " << size << endl;
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}
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// 8. Determine the list of true (i.e. parallel conforming) essential
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// boundary dofs. In this example, the boundary conditions are defined
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// by marking all the boundary attributes from the mesh as essential
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// (Dirichlet) and converting them to a list of true dofs.
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Array<int> ess_tdof_list;
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if (pmesh->bdr_attributes.Size())
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{
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Array<int> ess_bdr(pmesh->bdr_attributes.Max());
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ess_bdr = 1;
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fespace->GetEssentialTrueDofs(ess_bdr, ess_tdof_list);
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}
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// 9. Set up the parallel linear form b(.) which corresponds to the
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// right-hand side of the FEM linear system, which in this case is
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// (1,phi_i) where phi_i are the basis functions in fespace.
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ParLinearForm *b = new ParLinearForm(fespace);
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ConstantCoefficient one(1.0);
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b->AddDomainIntegrator(new DomainLFIntegrator(one));
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b->Assemble();
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// 10. Define the solution vector x as a parallel finite element grid function
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// corresponding to fespace. Initialize x with initial guess of zero,
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// which satisfies the boundary conditions.
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ParGridFunction x(fespace);
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x = 0.0;
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// 11. Set up the parallel bilinear form a(.,.) on the finite element space
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// corresponding to the Laplacian operator -Delta, by adding the Diffusion
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// domain integrator.
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ParBilinearForm *a = new ParBilinearForm(fespace);
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if (pa) { a->SetAssemblyLevel(AssemblyLevel::PARTIAL); }
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a->AddDomainIntegrator(new DiffusionIntegrator(one));
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// 12. Assemble the parallel bilinear form and the corresponding linear
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// system, applying any necessary transformations such as: parallel
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// assembly, eliminating boundary conditions, applying conforming
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// constraints for non-conforming AMR, static condensation, etc.
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if (static_cond) { a->EnableStaticCondensation(); }
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a->Assemble();
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OperatorPtr A;
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Vector B, X;
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a->FormLinearSystem(ess_tdof_list, x, *b, A, X, B);
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// 13. Solve the linear system A X = B.
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// If using MFEM with HYPRE
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// * With full assembly, use the BoomerAMG preconditioner from hypre.
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// * With partial assembly, use Jacobi smoothing, for now.
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// If using MFEM with PETSc
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// * With full assembly, use command line options or H2 matrix solver
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// * With partial assembly, wrap Jacobi smoothing, for now.
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Solver *prec = NULL;
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if (pa)
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{
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if (UsesTensorBasis(*fespace))
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{
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prec = new OperatorJacobiSmoother(*a, ess_tdof_list);
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}
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}
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else
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{
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prec = new HypreBoomerAMG;
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}
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if (!use_petsc)
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{
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CGSolver *pcg = new CGSolver(MPI_COMM_WORLD);
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if (prec) { pcg->SetPreconditioner(*prec); }
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pcg->SetOperator(*A);
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pcg->SetRelTol(1e-12);
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pcg->SetMaxIter(200);
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pcg->SetPrintLevel(1);
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pcg->Mult(B, X);
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delete pcg;
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}
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else
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{
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PetscPCGSolver *pcg;
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// If petscrc_file has been given, we convert the HypreParMatrix to a
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// PetscParMatrix; the user can then experiment with PETSc command line
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// options unless forcewrap is true.
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bool wrap = forcewrap ? true : (pa ? true : !strlen(petscrc_file));
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if (wrap)
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{
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pcg = new PetscPCGSolver(MPI_COMM_WORLD);
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pcg->SetOperator(*A);
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if (useh2)
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{
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delete prec;
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prec = new PetscH2Solver(*A.Ptr(),fespace);
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}
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else if (!pa) // We need to pass the preconditioner constructed from the HypreParMatrix
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{
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delete prec;
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HypreParMatrix *hA = A.As<HypreParMatrix>();
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prec = new HypreBoomerAMG(*hA);
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}
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if (prec) { pcg->SetPreconditioner(*prec); }
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}
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else // Not wrapping, pass the HypreParMatrix so that users can experiment with command line
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{
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HypreParMatrix *hA = A.As<HypreParMatrix>();
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pcg = new PetscPCGSolver(*hA, false);
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if (useh2)
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{
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delete prec;
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prec = new PetscH2Solver(*hA,fespace);
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}
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}
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pcg->iterative_mode = true; // iterative_mode is true by default with CGSolver
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pcg->SetRelTol(1e-12);
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pcg->SetAbsTol(1e-12);
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pcg->SetMaxIter(200);
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pcg->SetPrintLevel(1);
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UserMonitor mymon(a,b);
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if (visualization && petscmonitor)
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{
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pcg->SetMonitor(&mymon);
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pcg->iterative_mode = true;
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X.Randomize();
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}
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pcg->Mult(B, X);
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delete pcg;
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}
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// 14. Recover the parallel grid function corresponding to X. This is the
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// local finite element solution on each processor.
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a->RecoverFEMSolution(X, *b, x);
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// 15. Save the refined mesh and the solution in parallel. This output can
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// be viewed later using GLVis: "glvis -np <np> -m mesh -g sol".
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{
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ostringstream mesh_name, sol_name;
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mesh_name << "mesh." << setfill('0') << setw(6) << myid;
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sol_name << "sol." << setfill('0') << setw(6) << myid;
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ofstream mesh_ofs(mesh_name.str().c_str());
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mesh_ofs.precision(8);
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pmesh->Print(mesh_ofs);
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ofstream sol_ofs(sol_name.str().c_str());
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sol_ofs.precision(8);
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x.Save(sol_ofs);
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}
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// 16. Send the solution by socket to a GLVis server.
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if (visualization)
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{
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char vishost[] = "localhost";
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int visport = 19916;
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socketstream sol_sock(vishost, visport);
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sol_sock << "parallel " << num_procs << " " << myid << "\n";
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sol_sock.precision(8);
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sol_sock << "solution\n" << *pmesh << x << flush;
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}
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// 17. Free the used memory.
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if (delete_fec)
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{
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delete fec;
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}
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delete a;
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delete b;
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delete fespace;
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delete pmesh;
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delete prec;
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// We finalize PETSc
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MFEMFinalizePetsc();
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return 0;
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}
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