Stationary iterative methods are methods for solving a linear system of equations
 |
where 
is a given matrix and 
is a given vector. Stationary iterative methods can be expressed
in the simple form
 |
where neither 
nor 
depends upon the iteration count 
. The four main stationary methods are the Jacobi
method, Gauss-Seidel method, successive
overrelaxation method (SOR), and symmetric
successive overrelaxation method (SSOR).
The Jacobi method is based on solving for every variable locally with respect to the other variables; one iteration corresponds to solving for every variable once. It is easy to understand and implement, but convergence is slow.
The Gauss-Seidel method is similar to the Jacobi method except that it uses updated values as soon as they are available. It generally converges faster than the Jacobi method, although still relatively slowly.
The successive overrelaxation method can be derived from the Gauss-Seidel method
by introducing an extrapolation parameter 
. This method can converge faster than Gauss-Seidel by
an order of magnitude.
Finally, the symmetric successive overrelaxation method is useful as a preconditioner for nonstationary methods. However, it has no advantage over the successive overrelaxation method as a stand-alone iterative method.
