next up previous contents
Next: Sparse linear solvers Up: Advanced options Previous: Equations decomposition   Contents

Convergence Criteria

There are three different methods of declaring a convergence:

  1. absolute tolerance, relative tolerance and running for a specified number of iterations. In the absolute tolerance mode algorithm stops when an absolute difference in any of the variables is lower than the threshold.
  2. relative tolerance In this method I compute the difference between the new approximation and the old one for each of the variables and divide it by the previous(old) value of the variable (in case it is not equal to 0).
  3. number of iterations Here we let the algorithm run for the specified number of steps no matter what absolute or relative error was obtained before that and return the approximation on the last step as the result of the computation.

Dominik Wojtczak 2006-10-31