Preconditioners for MLFMM

A number of preconditioners are available when using the multilevel fast multipole method (MLFMM) (for advanced users only).

Note: It is recommended to use the default settings.
On the Solve/Run tab, in the Solution settings group, click the  Solver settings icon. On the Solver setting dialog, click the Advanced tab.


Figure 1. The Solver settings dialog (Advanced tab).
Block-Jacobi using LU-decomposition (64)
Preconditioner for an MLFMM solution where the inverses of the preconditioner are calculated and applied during every iteration step.
Note: Due to performance reasons, this is the recommended preconditioner.
Incomplete LU decomposition (ILU) (128)
Preconditioner for an MLFMM solution that uses an incomplete LU-decomposition of the matrix.
Multilevel FEM-MLFMM LU/diagonal decomposition (2010)
Preconditioner for a hybrid FEM / MLFMM solution that uses a multilevel sparse LU decomposition of the combined and partitioned system.

When using the parallel Solver, the factorisation type can be specified.

Block-Jacobi preconditioner of MLFMM one-level-up (4096)
Preconditioner for an MLFMM solution that uses LU-decomposition on entries in the boxes, one-level-up from the finest boxes.
Sparse approximate inverse (SPAI) (8192)
Preconditioner for an MLFMM solution.
Sparse LU (8193)
Preconditioner for an MLFMM solution that uses a sparse LU decomposition of the MLFMM near field matrix.

When using the parallel Solver, the factorisation type can be specified.

Note: The number in brackets corresponds to the value of the I3 field at the CG card.