analytical_nonlinear_poisson.cpp File Reference

#include <BasicFiniteElements.hpp>
#include <PoissonOperators.hpp>
#include <AuxPoissonFunctions.hpp>

Go to the source code of this file.

Classes
struct	ExactFunction
	Function. More...
struct	ExactFunctionGrad
	Exact gradient. More...
struct	ExactLaplacianFunction
	Laplacian of function. More...
struct	FunA
struct	DiffFunA
struct	VolRuleNonlinear

Functions
int	main (int argc, char *argv[])

Variables
static char	help [] = "...\n\n"

Function Documentation

main()

int main	(	int	argc,
		char *	argv[]
	)

< Volume element for the matrix

< Boundary element for the matrix

< Volume element to assemble vector

< Volume element to assemble vector

< Volume element evaluate error

< Volume element to Post-process results

< Null element do nothing

Examples

analytical_nonlinear_poisson.cpp.

Definition at line 86 of file analytical_nonlinear_poisson.cpp.

                                 {
 
  // Initialize PETSc
  MoFEM::Core::Initialize(&argc, &argv, (char *)0, help);
  // Create MoAB database
  moab::Core moab_core;              // create database
  moab::Interface &moab = moab_core; // create interface to database
 
  try {
 
    // Get command line options
    int order = 3;                    // default approximation order
    PetscBool flg_test = PETSC_FALSE; // true check if error is numerical error
    CHKERR PetscOptionsBegin(PETSC_COMM_WORLD, "", "Poisson's problem options",
                             "none");
    // Set approximation order
    CHKERR PetscOptionsInt("-order", "approximation order", "", order, &order,
                           PETSC_NULL);
    // Set testing (used by CTest)
    CHKERR PetscOptionsBool("-test", "if true is ctest", "", flg_test,
                            &flg_test, PETSC_NULL);
    ierr = PetscOptionsEnd();
    CHKERRG(ierr)
 
    // Create MoFEM database and link it to MoAB
    MoFEM::Core mofem_core(moab);           // create database
    MoFEM::Interface &m_field = mofem_core; // create interface to database
    // Register DM Manager
    CHKERR DMRegister_MoFEM("DMMOFEM"); // register MoFEM DM in PETSc
 
    // Create vector to store approximation global error
    Vec global_error;
    CHKERR PoissonExample::AuxFunctions(m_field).createGhostVec(&global_error);
 
    // First we crate elements, implementation of elements is problem
    // independent, we do not know yet what fields are present in the problem,
    // or even we do not decided yet what approximation base or spaces we are
    // going to use. Implementation of element is free from those constrains and
    // can be used in different context.
 
    // Elements used by KSP & DM to assemble system of equations
    boost::shared_ptr<ForcesAndSourcesCore>
        domain_lhs_fe; ///< Volume element for the matrix
    boost::shared_ptr<ForcesAndSourcesCore>
        boundary_lhs_fe; ///< Boundary element for the matrix
    boost::shared_ptr<ForcesAndSourcesCore>
        domain_rhs_fe; ///< Volume element to assemble vector
    boost::shared_ptr<ForcesAndSourcesCore>
        boundary_rhs_fe; ///< Volume element to assemble vector
    boost::shared_ptr<ForcesAndSourcesCore>
        domain_error; ///< Volume element evaluate error
    boost::shared_ptr<PoissonExample::PostProcFE>
        post_proc_volume; ///< Volume element to Post-process results
    boost::shared_ptr<ForcesAndSourcesCore> null; ///< Null element do nothing
    {
      // Add problem specific operators the generic finite elements to calculate
      // matrices and vectors.
      CHKERR PoissonExample::CreateFiniteElements(m_field)
          .createFEToAssembleMatrixAndVectorForNonlinearProblem(
              ExactFunction(), ExactLaplacianFunction(), FunA(), DiffFunA(),
              domain_lhs_fe, boundary_lhs_fe, domain_rhs_fe, boundary_rhs_fe,
              VolRuleNonlinear());
      // Add problem specific operators the generic finite elements to calculate
      // error on elements and global error in H1 norm
      CHKERR PoissonExample::CreateFiniteElements(m_field)
          .createFEToEvaluateError(ExactFunction(), ExactFunctionGrad(),
                                   global_error, domain_error);
      // Post-process results
      CHKERR PoissonExample::CreateFiniteElements(m_field)
          .creatFEToPostProcessResults(post_proc_volume);
    }
 
    // Get simple interface is simplified version enabling quick and
    // easy construction of problem.
    Simple *simple_interface;
    // Query interface and get pointer to Simple interface
    CHKERR m_field.getInterface(simple_interface);
 
    // Build problem with simple interface
    {
 
      // Get options for simple interface from command line
      CHKERR simple_interface->getOptions();
      // Load mesh file to database
      CHKERR simple_interface->loadFile();
 
      // Add field on domain and boundary. Field is declared by space and base
      // and rank. space can be H1. Hcurl, Hdiv and L2, base can be
      // AINSWORTH_LEGENDRE_BASE, DEMKOWICZ_JACOBI_BASE and more, where rank is
      // number of coefficients for dof.
      //
      // Simple interface assumes that there are four types of field; 1) defined
      // on body domain, 2) fields defined on body boundary, 3) skeleton field
      // defined on finite element skeleton. Finally data field is defined on
      // body domain. Data field is not solved but used for post-process or to
      // keep material parameters, etc. Here we using it to calculate
      // approximation error on elements.
 
      // Add domain filed "U" in space H1 and Legendre base, Ainsworth recipe is
      // used to construct base functions.
      CHKERR simple_interface->addDomainField("U", H1, AINSWORTH_LEGENDRE_BASE,
                                              1);
      // Add Lagrange multiplier field on body boundary
      CHKERR simple_interface->addBoundaryField("L", H1,
                                                AINSWORTH_LEGENDRE_BASE, 1);
      // Add error (data) field, we need only L2 norm. Later order is set to 0,
      // so this is piecewise discontinuous constant approx., i.e. 1 DOF for
      // element. You can use more DOFs and collate moments of error to drive
      // anisotropic h/p-adaptivity, however this is beyond this example.
      CHKERR simple_interface->addDataField("ERROR", L2,
                                            AINSWORTH_LEGENDRE_BASE, 1);
 
      // Set fields order domain and boundary fields.
      CHKERR simple_interface->setFieldOrder("U",
                                             order); // to approximate function
      CHKERR simple_interface->setFieldOrder("L",
                                             order); // to Lagrange multipliers
      CHKERR simple_interface->setFieldOrder(
          "ERROR", 0); // approximation order for error
 
      // Setup problem. At that point database is constructed, i.e. fields,
      // finite elements and problem data structures with local and global
      // indexing.
      CHKERR simple_interface->setUp();
    }
 
    // Get access to PETSC-MoFEM DM manager.
    // or more derails see
    // <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/index.html>
    // Form that point internal MoFEM data structures are linked with PETSc
    // interface. If DM functions contains string MoFEM is is MoFEM specific DM
    // interface function, otherwise DM function part of standard PETSc
    // interface.
 
    DM dm;
    // Get dm
    CHKERR simple_interface->getDM(&dm);
 
    // Set KSP context for DM. At that point only elements are added to DM
    // operators. Calculations of matrices and vectors is executed by KSP
    // solver. This part of the code makes connection between implementation of
    // finite elements and data operators with finite element declarations in DM
    // manager. From that point DM takes responsibility for executing elements,
    // calculations of matrices and vectors, and solution of the problem.
    {
      // Set operators for SNES solver
      CHKERR DMMoFEMSNESSetJacobian(dm, simple_interface->getDomainFEName(),
                                    domain_lhs_fe, null, null);
      CHKERR DMMoFEMSNESSetJacobian(dm, simple_interface->getBoundaryFEName(),
                                    boundary_lhs_fe, null, null);
      // Set calculation of the right hand side vector for KSP solver
      CHKERR DMMoFEMSNESSetFunction(dm, simple_interface->getDomainFEName(),
                                    domain_rhs_fe, null, null);
      CHKERR DMMoFEMSNESSetFunction(dm, simple_interface->getBoundaryFEName(),
                                    boundary_rhs_fe, null, null);
    }
 
    // Solve problem, only PETEc interface here.
    {
 
      // Create the right hand side vector and vector of unknowns
      Vec F, D;
      CHKERR DMCreateGlobalVector(dm, &F);
      // Create unknown vector by creating duplicate copy of F vector. only
      // structure is duplicated no values.
      CHKERR VecDuplicate(F, &D);
 
      // Create solver and link it to DM
      SNES solver;
      CHKERR SNESCreate(PETSC_COMM_WORLD, &solver);
      CHKERR SNESSetFromOptions(solver);
      CHKERR SNESSetDM(solver, dm);
      // Set-up solver, is type of solver and pre-conditioners
      CHKERR SNESSetUp(solver);
      // At solution process, KSP solver using DM creates matrices, Calculate
      // values of the left hand side and the right hand side vector. then
      // solves system of equations. Results are stored in vector D.
      CHKERR SNESSolve(solver, F, D);
 
      // Scatter solution on the mesh. Stores unknown vector on field on the
      // mesh.
      CHKERR DMoFEMMeshToGlobalVector(dm, D, INSERT_VALUES, SCATTER_REVERSE);
 
      // Clean data. Solver and vector are not needed any more.
      CHKERR SNESDestroy(&solver);
      CHKERR VecDestroy(&D);
      CHKERR VecDestroy(&F);
    }
 
    // Calculate error
    {
      // Loop over all elements in mesh, and run users operators on each
      // element.
      CHKERR DMoFEMLoopFiniteElements(dm, simple_interface->getDomainFEName(),
                                      domain_error);
      CHKERR PoissonExample::AuxFunctions(m_field).assembleGhostVector(
          global_error);
      CHKERR PoissonExample::AuxFunctions(m_field).printError(global_error);
      if (flg_test == PETSC_TRUE) {
        CHKERR PoissonExample::AuxFunctions(m_field).testError(global_error);
      }
    }
 
    {
      // Loop over all elements in the mesh and for each execute
      // post_proc_volume element and operators on it.
      CHKERR DMoFEMLoopFiniteElements(dm, simple_interface->getDomainFEName(),
                                      post_proc_volume);
      // Write results
      post_proc_volume->writeFile("out_vol.h5m");
    }
 
    // Destroy DM, no longer needed.
    CHKERR DMDestroy(&dm);
 
    // Destroy ghost vector
    CHKERR VecDestroy(&global_error);
  }
  CATCH_ERRORS;
 
  // finish work cleaning memory, getting statistics, etc.
  MoFEM::Core::Finalize();
 
  return 0;
}

Variable Documentation

help

char help[] = "...\n\n"

static

Examples

analytical_nonlinear_poisson.cpp.

Definition at line 20 of file analytical_nonlinear_poisson.cpp.