PCILU

Incomplete factorization preconditioners.

Options Database Keys

-pc_ilu_levels <k> - number of levels of fill for ILU(k)
-pc_ilu_in_place - only for ILU(0) with natural ordering, reuses the space of the matrix for its factorization (overwrites original matrix)
-pc_ilu_diagonal_fill - fill in a zero diagonal even if levels of fill indicate it wouldn't be fill
-pc_ilu_reuse_ordering - reuse ordering of factorized matrix from previous factorization
-pc_ilu_damping - add damping to diagonal to prevent zero (or very small) pivots
-pc_ilu_shift - apply Manteuffel shift to diagonal to force positive definite preconditioner
-pc_ilu_zeropivot <tol> - set tolerance for what is considered a zero pivot
-pc_ilu_use_drop_tolerance <dt,dtcol,maxrowcount> - use Saad's drop tolerance ILUdt
-pc_ilu_fill <nfill> - expected amount of fill in factored matrix compared to original matrix, nfill > 1
-pc_ilu_nonzeros_along_diagonal - reorder the matrix before factorization to remove zeros from the diagonal, this decreases the chance of getting a zero pivot
-pc_ilu_mat_ordering_type <natural,nd,1wd,rcm,qmd> - set the row/column ordering of the factored matrix
-pc_ilu_pivot_in_blocks - for block ILU(k) factorization, i.e. with BAIJ matrices with block size larger than 1 the diagonal blocks are factored with partial pivoting (this increases the stability of the ILU factorization

Notes: Only implemented for some matrix formats. Not implemented in parallel

For BAIJ matrices this implements a point block ILU

See Also

PCCreate(), PCSetType(), PCType (for list of available types), PC, PCSOR, MatOrderingType,
PCILUSetSetZeroPivot(), PCILUSetDamping(), PCILUSetShift(), PCILUSetUseDropTolerance(), PCILUSetFill(), PCILUSetMatOrdering(), PCILUSetReuseOrdering(), PCILUDTSetReuseFill(), PCILUSetLevels(), PCILUSetUseInPlace(), PCILUSetAllowDiagonalFill(), PCILUSetPivotInBlocks(),

Level:beginner
Location:
src/ksp/pc/impls/ilu/ilu.c
Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages

Examples

src/ksp/pc/examples/tutorials/ex1.c.html
src/ksp/examples/tutorials/ex7.c.html
src/ksp/examples/tutorials/ex8.c.html