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I'm writing a program that calculates the velocity of a certain current around an object like for example a square. Now, I use the Jacobi Iteration method and when I run it the results aren't what I'm expecting. I have no idea what I'am doing wrong. I have 2 classes, one that makes a Grid that I cant adjust, and another that creates an object with a parameter 'voneindig'.

If I make a square and a grid and run the Iterate() function it seems to happen that my square object becomes bigger. ( I get more and more zero's around my original square )

the member function getStatusElement() is a grid I've made with one's where the square is located and zero's elsewhere.

    void Object::Iterate()
{
double gem=1, jacobielement, som; //locale variabelen
double epsilon=pow(10,-5); //convergentiecriterium
const int d= grid1.GetDimension(); //dimension of the grid
while(gem > epsilon)
{
  for( int i = 0; i < d; i++ )
  {
    for( int j = 0; j < d; j++ )
    {
    grid2.SetElement(i,j,grid1.GetElement(i,j));
    }
  }

  for(int i=1; i<d-1; ++ i)
  {
    for(int j=1; j<d-1; ++ j)
    {
        if( grid1.getStatusElement(i,j) == 0 )
        {//jacobie
        jacobielement= (grid1.GetElement(i,j+1) + grid1.GetElement(i,j-1) + grid1.GetElement(i+1,j) + grid1.GetElement(i-1,j))/4;

        grid1.SetElement(i,j,jacobielement);
        }
    }
  }
  som=0;
  for(int i=0; i<d; ++ i){
    for(int j=0;j<d; ++ j){
    //Convergention
    som=som+std::abs(grid1.GetElement(i,j)-grid2.GetElement(i,j));
    }
  }
  gem= som/pow(d,2);
}
}

I hope I've given enoug information for this problem, otherwise I can give you all my code. Thanks alot!

ComputerSaysNo
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  • This probably doesn't help, but I would suggest you use Python + numpy + scipy + matplotlib instead (the Enthought version of Python has all these) -- there may be some predefined libraries for doing this computation, and you wouldn't have to mess around with C/C++ issues. Python may not be quite as fast as C/C++ for numeric programming but it's not bad. – Jason S Apr 02 '13 at 22:43
  • in particular: http://www.scipy.org/PerformancePython#head-a73fa06d3c4f3bda71b3526d30d51c492d8f80df – Jason S Apr 02 '13 at 22:44

0 Answers0