gf_precond

The preconditioners may store REAL or COMPLEX values. They accept getfem sparse matrices and Matlab sparse matrices.

# Calling Sequence

    PC = gf_precond('identity')

    PC = gf_precond('cidentity')

    PC = gf_precond('diagonal', vec D)

    PC = gf_precond('ildlt', spmat m)

    PC = gf_precond('ilu', spmat m)

    PC = gf_precond('ildltt', spmat m[, int fillin[, scalar threshold]])

    PC = gf_precond('ilut', spmat m[, int fillin[, scalar threshold]])

    PC = gf_precond('superlu', spmat m)

    PC = gf_precond('spmat', spmat m)

## Description

General constructor for precond objects.

The preconditioners may store REAL or COMPLEX values. They accept getfem sparse matrices and Matlab sparse matrices.

## Command list

- `PC = gf_precond('identity')`

  Create a REAL identity precondioner.

- `PC = gf_precond('cidentity')`

  Create a COMPLEX identity precondioner.

- `PC = gf_precond('diagonal', vec D)`

  Create a diagonal precondioner.

- `PC = gf_precond('ildlt', spmat m)`

  Create an ILDLT (Cholesky) preconditioner for the (symmetric) sparse matrix `m`. This preconditioner has the same sparsity pattern than `m` (no fill-in).

- `PC = gf_precond('ilu', spmat m)`

  Create an ILU (Incomplete LU) preconditioner for the sparse matrix `m`. This preconditioner has the same sparsity pattern than `m` (no fill-in).

- `PC = gf_precond('ildltt', spmat m[, int fillin[, scalar threshold]])`

  Create an ILDLTT (Cholesky with filling) preconditioner for the (symmetric) sparse matrix `m`. The preconditioner may add at most `fillin` additional non-zero entries on each line. The default value for `fillin` is 10, and the default threshold is1e-7.

- `PC = gf_precond('ilut', spmat m[, int fillin[, scalar threshold]])`

  Create an ILUT (Incomplete LU with filling) preconditioner for the sparse matrix `m`. The preconditioner may add at most `fillin` additional non-zero entries on each line. The default value for `fillin` is 10, and the default threshold is 1e-7.

- `PC = gf_precond('superlu', spmat m)`

  Uses SuperLU to build an exact factorization of the sparse matrix `m`. This preconditioner is only available if the getfem-interface was built with SuperLU support. Note that LU factorization is likely to eat all your memory for 3D problems.

- `PC = gf_precond('spmat', spmat m)`

  Preconditionner given explicitely by a sparse matrix.

## See Also

- getfem types

## Authors

Y. Collette