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# MatILUFactorSymbolic

Performs symbolic ILU factorization of a matrix obtained with `MatGetFactor()` Uses levels of fill only, not drop tolerance. Use `MatLUFactorNumeric()` to complete the factorization.

## Synopsis

    #include "petscmat.h"
    PetscErrorCode MatILUFactorSymbolic(Mat fact, Mat mat, IS row, IS col, const MatFactorInfo *info)

Collective

## Input Parameters

- fact - the factorized matrix obtained with `MatGetFactor()`

- mat - the matrix

- row - row permutation

- col - column permutation

- info - structure containing

          levels - number of levels of fill.
          expected fill - as ratio of original fill.
          1 or 0 - indicating force fill on diagonal (improves robustness for matrices
                    missing diagonal entries)

## Notes

See Matrix Factorization for additional information.

Most users should employ the `KSP` interface for linear solvers instead of working directly with matrix algebra routines such as this. See, e.g., `KSPCreate()`.

Uses the definition of level of fill as in Y. Saad, [Saa03]

## Fortran Note

A valid (non-null) `info` argument must be provided

## References

[Saa03]

Yousef Saad. Iterative Methods for Sparse Linear Systems. SIAM, 2nd edition, 2003. doi:10.1016/S1570-579X(01)80025-2.

## See Also

Matrices, `Mat`, Matrix Factorization, `MatGetFactor()`, `MatLUFactorSymbolic()`, `MatLUFactorNumeric()`, `MatCholeskyFactor()`, `MatGetOrdering()`, `MatFactorInfo`

## Level

developer

## Location

src/mat/interface/matrix.c

## Implementations

MatILUFactorSymbolic_SeqAIJ() in src/mat/impls/aij/seq/aijfact.c
MatILUFactorSymbolic_SeqAIJKokkos() in src/mat/impls/aij/seq/kokkos/aijkok.kokkos.cxx
MatILUFactorSymbolic_SeqAIJCUSPARSE() in src/mat/impls/aij/seq/seqcusparse/aijcusparse.cu
MatILUFactorSymbolic_SeqAIJHIPSPARSE() in src/mat/impls/aij/seq/seqhipsparse/aijhipsparse.hip.cxx
MatILUFactorSymbolic_SeqBAIJ() in src/mat/impls/baij/seq/baijfact2.c

Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages