EVPHarmonicEasy_lapack.cpp File Reference

Solves the harmonic equation. More...

#include <EVP_bundle.h>
#include <Utility.h>
#include "../Utils_Fill.h"

Go to the source code of this file.

Classes
class	CppNoddy::Example::harmonic_equation
	Define the harmonic equation by inheriting the Equation base class. More...
class	CppNoddy::Example::harmonic_both_BC

Namespaces
namespace	CppNoddy
	A collection of OO numerical routines aimed at simple (typical) applied problems in continuum mechanics.
namespace	CppNoddy::Example

Enumerations
enum	{ f , fd }

Functions
int	main ()

Detailed Description

Solves the harmonic equation.

as an eigenvalue problem for over the unit domain with homogeneous boundary conditions for , returning the smallest eigenvalue. This is the 'easy' approach, using the ODE_EVP class which is constructed from an Equation_with_mass object, with Residual objects for the boundary conditions. The solver then only needs a pointer to the eigenvalue variable.

Definition in file EVPHarmonicEasy_lapack.cpp.

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
f
fd

Definition at line 18 of file EVPHarmonicEasy_lapack.cpp.

{f, fd };

Function Documentation

main()

int main

(

)

Definition at line 72 of file EVPHarmonicEasy_lapack.cpp.

{
  cout << "\n";
  cout << "=== EVP: The harmonic equation done the easy way ====\n";
  cout << "\n";
 
  // test pass/fail
  bool failed( true );
 
 
  Example::harmonic_equation problem;
  Example::harmonic_both_BC BC_both;
  // domain is 0 to 1
  double left = 0.0;
  double right = 1.0;
  // number of nodal points
  int N = 256;
  // EV is pi^2 so we'll guess = 10 + 0i
  D_complex guess( 10.0, 0.0 );
  // pass/fail tolerance
  const double tol = 1.e-3;
 
  cout << " Solving the system using LAPACK:\n";
  // set up the ode eigenproblem
  ODE_EVP<double> ode_lapack( &problem, Utility::uniform_node_vector( left, right, N ), &BC_both, &BC_both );
  ode_lapack.p_eigensystem() -> set_calc_eigenvectors( true );
  ode_lapack.p_eigensystem() -> set_shift( guess );
  try
  {
    // solve the global eigenvalue
    ode_lapack.eigensolve();
  }
  catch (const std::runtime_error &error )
  {
    cout << " \033[1;31;48m  * FAILED THROUGH EXCEPTION BEING RAISED \033[0m\n";
    return 1;
  }
  // get the eigenvalues in a disk of radius 1 about the guess
  ode_lapack.p_eigensystem() -> tag_eigenvalues_disc( + 1, 1. );
  // get the tagged eigenvalue(s) -- hopefully only 1
  DenseVector<D_complex> lapack_lambdas = ode_lapack.p_eigensystem() -> get_tagged_eigenvalues();
  if ( abs( lapack_lambdas[ 0 ].real() - M_PI * M_PI ) < tol )
  {
    failed = false;
    cout << "  LAPACK solver works.\n";
  }
 
  if ( failed )
  {
    cout << "\033[1;31;48m  * FAILED \033[0m\n";
    return 1;
  }
 
  cout << "\033[1;32;48m  * PASSED \033[0m\n";
  return 0;
 
}

References CppNoddy::ODE_EVP< _Type >::eigensolve(), CppNoddy::ODE_EVP< _Type >::p_eigensystem(), and CppNoddy::Utility::uniform_node_vector().