Added biharmonic example in libceed

examples/mfem/biharmonic.cpp

@@ -0,0 +1,101 @@
+// Copyright (c) 2017-2024, Lawrence Livermore National Security, LLC and other CEED contributors.
+// All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
+//
+// SPDX-License-Identifier: BSD-2-Clause
+//
+// This file is part of CEED:  http://github.com/ceed
+
+//                         libCEED + MFEM Example: BP6
+//
+// This example illustrates a simple usage of libCEED with the MFEM (mfem.org) finite element library.
+//
+// It solves the biharmonic equation \Nabla^2 u =f on Omega, u(\vec{x})=0 on ∂(Omega), du/d(\vec{x})*n=0 on ∂(Omega) by solving -\Nabla w=f, -\Nabla u=w
+// 
+// 
+//
+
+
+/// @file
+/// MFEM mass operator based on libCEED
+#include <mfem.hpp>
+#include <mfem/libceed/mfem-ceed.hpp>
+#include <ceed.h>
+#include <ceed-backend.h>
+#include <ceed-examples.h>  
+#include <fstream>
+#include <iostream>
+
+using namespace mfem;
+
+int main(int argc, char *argv[])
+{
+   // 1. Initialize MFEM and CEED
+  Device device("cpu");
+  std::cout << "\nRunning on device: " << device.GetDeviceMemoryTypeName() << "\n\n";
+
+  Ceed ceed;
+  CeedInit("/cpu/self", &ceed);
+
+  // 2. Read mesh from file
+  const char *mesh_file = "mesh.mesh";
+  Mesh mesh(mesh_file, 1, 1, true); // generate_edges = 1, refine = 1, fix_orientation = true
+  mesh.EnsureNodes();
+  int dim = mesh.Dimension();
+
+
+  // 3. Set up finite element space
+  H1_FECollection fec(order, dim);
+  FiniteElementSpace fespace(&mesh, &fec);
+
+  std::cout << "Number of finite element unknowns: " << fespace.GetTrueVSize() << std::endl;
+
+  // 4. Load source function f from file
+  GridFunction rhs(&fespace);
+  std::ifstream fin("f.gf");
+  if (!fin)
+  {
+    std::cerr << "Error: Unable to open file 'f.gf'.\n";
+    return 1;
+  }
+  rhs.Load(fin);
+
+  // 5. set up intermediate grid functions
+  GridFunction w(&fespace);
+  GridFunction u(&fespace);
+
+  // 6. Use CEED built-in QFunctions for Laplacian
+  CeedQFunction qf_build, qf_apply;
+  CeedQFunctionCreateInterior(ceed, 1, f_build_diff, "f_build_diff", &qf_build);
+  CeedQFunctionAddInput(qf_build, "dx", CEED_EVAL_GRAD, dim);
+  CeedQFunctionAddOutput(qf_build, "qdata", CEED_EVAL_NONE, dim*(dim+1)/2);
+
+  CeedQFunctionCreateInterior(ceed, 1, f_apply_diff, "f_apply_diff", &qf_apply);
+  CeedQFunctionAddInput(qf_apply, "u", CEED_EVAL_INTERP, 1);
+  CeedQFunctionAddInput(qf_apply, "grad_u", CEED_EVAL_GRAD, dim);
+  CeedQFunctionAddInput(qf_apply, "qdata", CEED_EVAL_NONE, dim*(dim+1)/2);
+  CeedQFunctionAddOutput(qf_apply, "v", CEED_EVAL_INTERP, 1);
+
+  // 7. Build CEED operator with MFEM wrapper
+  mfem::ceed::CeedOperatorBuilder builder(&fespace, qf_apply, qf_build, ceed);
+  CeedOperator ceed_op = builder.GetCeedOperator();
+
+   // 8. Create CEED linear solver
+  mfem::ceed::CeedSolver solver(ceed_op);
+
+  // 9. Solve -Δ w = f and -Δ u = w
+  std::cout << "Solving -Δ w = f...\n";
+  solver.Solve(rhs, w);
+
+
+  std::cout << "Solving -Δ u = w...\n";
+  solver.Solve(w, u);
+
+  // 10. Save solutions
+  std::ofstream ufile("u.gf");
+  u.Save(ufile);
+  std::cout << "Solutions saved to 'u.gf' .\n";
+
+  // 11. destroy
+  CeedDestroy(&ceed);
+  return 0;
+}

examples/mfem/biharmonic.h

@@ -0,0 +1,38 @@
+#ifndef BIHARMONIC_H
+#define BIHARMONIC_H
+
+#include <mfem.hpp>
+#include <ceed.h>
+#include <string>
+
+namespace biharmonic
+{
+   // Initialize the MFEM device (e.g., CPU, GPU).
+   void InitializeDevice();
+
+   // Initialize the libCEED context with the specified resource.
+   void InitializeCeed(Ceed &ceed, const std::string &resource = "/cpu/self");
+
+   // Load the mesh from a file and perform uniform refinements.
+   mfem::Mesh *LoadMesh(const std::string &mesh_file, int ref_levels = 1);
+
+   // Set up the finite element space with the given polynomial order.
+   mfem::FiniteElementSpace *SetupFESpace(mfem::Mesh *mesh, int order);
+
+   // Load the right-hand side function 'f' from a file into a GridFunction.
+   mfem::GridFunction *LoadRHS(const std::string &rhs_file, mfem::FiniteElementSpace *fespace);
+
+   // Set up the CEED QFunctions for the Laplacian operator.
+   void SetupQFunctions(Ceed ceed, CeedQFunction &qf_build, CeedQFunction &qf_apply, int dim);
+
+   // Build the CEED operator using the MFEM wrapper.
+   CeedOperator BuildCeedOperator(mfem::FiniteElementSpace *fespace, CeedQFunction qf_apply, CeedQFunction qf_build, Ceed ceed);
+
+   // Solve the equation using the CEED solver.
+   void Solve(CeedOperator ceed_op, mfem::GridFunction &rhs, mfem::GridFunction &solution);
+
+   // Save the solution to a file.
+   void SaveSolution(const mfem::GridFunction &solution, const std::string &filename);
+}
+
+#endif // BIHARMONIC_H

examples/mfem/biharmonic.hpp

@@ -0,0 +1,37 @@
+#ifndef BIHARMONIC_HPP
+#define BIHARMONIC_HPP
+
+#include <mfem.hpp>
+#include <ceed.h>
+
+namespace biharmonic
+{
+   // Initializes the MFEM device.
+   void InitializeDevice();
+
+   // Initializes the libCEED context.
+   void InitializeCeed(Ceed &ceed, const std::string &resource = "/cpu/self");
+
+   // Loads the mesh from a file and prepares it.
+   mfem::Mesh *LoadMesh(const std::string &mesh_file, int ref_levels);
+
+   // Sets up the finite element space.
+   mfem::FiniteElementSpace *SetupFESpace(mfem::Mesh *mesh, int order);
+
+   // Loads the source function 'f' from a file.
+   mfem::GridFunction *LoadRHS(const std::string &rhs_file, mfem::FiniteElementSpace *fespace);
+
+   // Sets up the CEED QFunctions for the Laplacian.
+   void SetupQFunctions(Ceed ceed, CeedQFunction &qf_build, CeedQFunction &qf_apply, int dim);
+
+   // Builds the CEED operator using the MFEM wrapper.
+   CeedOperator BuildCeedOperator(mfem::FiniteElementSpace *fespace, CeedQFunction qf_apply, CeedQFunction qf_build, Ceed ceed);
+
+   // Solves the equation using the CEED solver.
+   void Solve(CeedOperator ceed_op, mfem::GridFunction &rhs, mfem::GridFunction &solution);
+
+   // Saves the solution to a file.
+   void SaveSolution(const mfem::GridFunction &solution, const std::string &filename);
+}
+
+#endif // BIHARMONIC_HPP