Pre-elimination

  Due to the boundary conditions or interface conditions it is possible, that the system matrix can become ill-conditioned during solving. The rows which degrade the condition of the system matrix are determined and marked for pre-elimination. The pre-elimination itself is done by the Gauß elimination method.

To solve the pre-eliminated matrix three stages have to be performed successively: (1) scaling of the whole system, (2) pre-conditioning and, finally, (3) solving the equation by numerical algorithms.