1. But

Linear solvers are in fact omnipresent in the flow of Code_Aster operators because they are often buried in the depths of other numerical algorithms: non-linear schema, time integration, modal analysis etc. They often consume most of the CPU time and memory. The choice and complete configuration of the required linear solver is made*via* the keyword factor SOLVEUR. It is present in most calculation commands (STAT_NON_LINE, THER_LINEAIRE, CALC_MODES etc.).

This user manual is complementary to the User documentation for the keyword SOLVEUR [U4.50.01]. It is intended to be an intermediate link between « simple » keyword documentation and theoretical documentation (each solver is backed by reference documentation).

The first part of this note gives an overview of the various linear solvers available, their scope of use and their average performances in terms of robustness and CPU /memory consumption.

The next chapter contains some advice to make the best use of the SOLVEUR parameters depending on the case: the size of the system, its numerical properties, the CPU and memory consumption… Finally, we detail some parameters of SOLVEUR in order to help the user in advanced usage of this code feature.

The related problems of improving the performance (RAM/CPU) of a calculation and the use of parallelism are also briefly addressed. They are the subject of specific notices, respectively, [U1.03.03] and [U2.08.06].