Re: [Libmesh-users] Nodal data with ExplicitSystem

[Andrew E S. <and...@gm...>]

Program works if I use a wrapper function instead of AnalyticFunction,
perhaps I am not using it correctly or there is a bug. The code that works
is below, the AnalyticFunction stuff that, at least as I understand, should
also work is commented out.

If anyone has any information on why this problem exists I would
appreciated it, I prefer using AnalyticFunction if I can.

Peace,
Andrew

--- PROGRAM ---

// Standard library includes
#include <iostream>
#include <algorithm>
#include <math.h>
#include <stdio.h>

// libMesh includes
#include "libmesh.h"
#include "mesh.h"
#include "mesh_generation.h"
#include "equation_systems.h"
#include "transient_system.h"
#include "explicit_system.h"
#include "analytic_function.h"
#include "vtk_io.h"
#include "exodusII_io.h"

// Bring in everything from the libMesh namespace
using namespace libMesh;

// A function for initilizing thermal conductivity
#include <boost/math/constants/constants.hpp>
Number initial_conductivity (const Point& p, const Real t = 0){
const double pi = boost::math::constants::pi<double>();
return 1 + exp(-t) * sin(pi*p(0)) * sin(pi*p(1));
}

// Wrapper function for exact solution, used for initilization
Number initial_function(const Point& p, const Parameters&, const
std::string&, const std::string&){
    return initial_conductivity(p, 0.0);
}

// Begin main function
int main (int argc, char** argv){

// Initialize libraries
    LibMeshInit init (argc, argv);

// Generate a mesh
Mesh mesh;
MeshTools::Generation::build_square(mesh, 10, 10, 0., 1, 0., 1, QUAD8);
mesh.all_second_order();

// Create a system for storing nodal values of conductivity
EquationSystems eq_sys(mesh);
eq_sys.add_system<TransientExplicitSystem>("data");
eq_sys.get_system("data").add_variable("k", SECOND, MONOMIAL);
eq_sys.init();
 // Project the initial values of conductivity
//eq_sys.get_system("data").time = 0;
//AnalyticFunction<Number> func_object(initial_conductivity);
//eq_sys.get_system("data").project_solution(&func_object);
eq_sys.get_system("data").project_solution(initial_function, NULL,
eq_sys.parameters);

// Write conductivity values to a file
ExodusII_IO(mesh).write_equation_systems("example3.ex2", eq_sys);
return 0;
}


On Wed, Jun 6, 2012 at 2:28 PM, Andrew E Slaughter <
and...@gm...> wrote:

> I searched through the mailings lists and found some discussion that
> explains that nodal and element data should be stored in an ExplicitSystem,
> but could not find any example or explanation to how it should be done.
>
> So, I am working on a test program, but run into a problem when projecting
> a "solution". What I am attempting to do in my test code is to create a
> TransientExplicitSystem to store a parameter (conductivity). Then using an
> equation, I initialize the value across the mesh via projection (I imagine
> that I should be able to use projection at any point in time to alter the
> values).
>
> The program compiles and links, but produces a PETSc segmentation fault
> when executed. I don't understand the concept of using systems for data
> storing so I don't have a good feel for what I might be doing wrong.
>
> I would greatly appreciate any help getting this up and running or any
> recommendations in general for storing and updating nodal and/or elemental
> data.
>
> Thanks,
> Andrew
>
> --- MY PROGRAM ---------
>
> // Standard library includes
> #include <iostream>
> #include <algorithm>
> #include <math.h>
> #include <stdio.h>
>
> // libMesh includes
> #include "libmesh.h"
> #include "mesh.h"
> #include "mesh_generation.h"
> #include "equation_systems.h"
> #include "transient_system.h"
> #include "explicit_system.h"
> #include "analytic_function.h"
> #include "vtk_io.h"
>
> // Bring in everything from the libMesh namespace
> using namespace libMesh;
>
> // A function for initilizing thermal conductivity
> #include <math.h>
> #include <boost/math/constants/constants.hpp>
> Number initial_conductivity (const Point& p, const Real t){
>  const double pi = boost::math::constants::pi<double>();
> return 1 + exp(-t) * sin(pi*p(0)) * sin(pi*p(1));
> }
>
> // Begin main function
> int main (int argc, char** argv){
>
> // Initialize libraries
>     LibMeshInit init (argc, argv);
>
> // Generate a mesh
> Mesh mesh;
> MeshTools::Generation::build_square(mesh, 10, 10, 0., 1, 0., 1, QUAD4);
>  mesh.all_second_order();
>
> // Create a system for storing nodal values of conductivity
>  EquationSystems eq_sys(mesh);
> eq_sys.add_system<TransientExplicitSystem>("data");
>  eq_sys.get_system("data").add_variable("k", SECOND, MONOMIAL);
> eq_sys.init();
>  // Project the initial values of conductivity
> AnalyticFunction<Number> func_object(initial_conductivity);
>  eq_sys.get_system("data").project_solution(&func_object); //
> segmentation fault here
>
> // Write conductivity values to a file
>  //...
>
> return 0;
> }
>
> --
> Andrew E. Slaughter, PhD
> and...@gm...
>
> Materials Process Design and Control Laboratory
> Sibley School of Mechanical and Aerospace Engineering
> 169 Frank H. T. Rhodes Hall
> Cornell University
> Ithaca, NY 14853-3801
> (607) 229-1829
>



-- 
Andrew E. Slaughter, PhD
and...@gm...

Materials Process Design and Control Laboratory
Sibley School of Mechanical and Aerospace Engineering
169 Frank H. T. Rhodes Hall
Cornell University
Ithaca, NY 14853-3801
(607) 229-1829