Simple Example

The code below shows a simple code for solving Poisson's equation by Gauss-Seidel. The pure code can be found here. .

#include "source/staggex.h"

double sinus (double x){
  return sin(x);
}


double sinush (double x){
  return sinh(x);
}


int main(int argc, char** argv)
{
  cout.precision(10);
  cout.setf(std::ios::fixed,std::ios::floatfield);

  std::ifstream PARAMETER;
  int n, iteration;

  ofstream DATEI;

  PARAMETER.open("para.dat",std::ios::in);
  PARAMETER >> n >> iteration;
  PARAMETER.close();

  cout << "\n Solving bla \n";
  cout << "\n n: " << n;

  Staggered_grid grid(n,n,n,
		      D3vector(0.0,0.0,0.0),
		      D3vector(1.0,1.0,1.0));


  Variable<double,not_staggered,not_staggered,not_staggered> u(grid);
  Variable<double,not_staggered,not_staggered,not_staggered> u_ex(grid);
  Variable<double,not_staggered,not_staggered,not_staggered> err(grid);


  Coordinate<WE_dir> X(grid);
  Coordinate<SN_dir> Y(grid);
  Coordinate<DT_dir> Z(grid);


  //GAUSS Seidel
  Function1 Sin(sinus);
  Function1 Sinh(sinush);


  // u_ex = X*Y;
  u_ex = Sin( X * M_PI ) * Sinh( Y * M_PI);   // exact solution

  u    = u_ex;

  for(int i=0; i < iteration;++i) {
    u = (E(E(u)) + W(W(u)) + N(N(u)) + S(S(u)) + T(T(u)) + D(D(u))) / 6.0;
    err = u - u_ex;
    cout << " error: " << L_infty(err) << endl;
  }
  



  DATEI.open("u.dx",std::ios :: out);
  u.Print_Dx(&DATEI);
  DATEI.close();

  cout << " end! " << endl;
}


      

Last modified: Wed Jun 6 10:14:54 PDT 2001