petsc-3.12.4 2020-02-04
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# MatMatMultSymbolic

Performs construction, preallocation, and computes the ij structure of the matrix-matrix product C=A*B. Call this routine before calling MatMatMultNumeric().

### Synopsis

    #include "petscmat.h"
    PetscErrorCode MatMatMultSymbolic(Mat A,Mat B,PetscReal fill,Mat *C)

Neighbor-wise Collective on Mat

### Input Parameters

| A | - the left matrix
| B | - the right matrix
| fill | - expected fill as ratio of nnz(C)/(nnz(A) + nnz(B)), use PETSC_DEFAULT if you do not have a good estimate, if C is a dense matrix this is irrelevent

### Output Parameters

C -the product matrix

### Notes

To determine the correct fill value, run with -info and search for the string "Fill ratio" to see the value actually needed.

This routine is currently implemented for - pairs of AIJ matrices and classes which inherit from AIJ, C will be of type AIJ - pairs of AIJ (A) and Dense (B) matrix, C will be of type Dense. - pairs of Dense (A) and AIJ (B) matrix, C will be of type Dense.

Developers Note: There are ways to estimate the number of nonzeros in the resulting product, see for example, https://arxiv.org/abs/1006.4173 We should incorporate them into PETSc.

### See Also

MatMatMult(), MatMatMultNumeric()

### Level

intermediate

### Location

src/mat/interface/matrix.c

### Examples

src/tao/pde_constrained/examples/tutorials/elliptic.c.html
src/tao/pde_constrained/examples/tutorials/parabolic.c.html

### Implementations

MatMatMultSymbolic_MPIDense_MPIAIJ in src/mat/impls/aij/mpi/mpiaij.c
MatMatMultSymbolic_MPIAIJ_MPIAIJ_nonscalable in src/mat/impls/aij/mpi/mpimatmatmult.c
MatMatMultSymbolic_MPIAIJ_MPIDense in src/mat/impls/aij/mpi/mpimatmatmult.c
MatMatMultSymbolic_MPIAIJ_MPIAIJ in src/mat/impls/aij/mpi/mpimatmatmult.c
MatMatMultSymbolic_MPIAIJ_MPIAIJ_seqMPI in src/mat/impls/aij/mpi/mpimatmatmult.c
MatMatMultSymbolic_SeqDense_SeqAIJ in src/mat/impls/aij/seq/aij.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_LLCondensed in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable_fast in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_Scalable in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_Heap in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_BTHeap in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_RowMerge in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqAIJ_Sorted in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqAIJ_SeqDense in src/mat/impls/aij/seq/matmatmult.c
MatMatMultSymbolic_SeqBAIJ_SeqDense in src/mat/impls/baij/seq/baij2.c
MatMatMultSymbolic_MPIDense_MPIDense in src/mat/impls/dense/mpi/mpidense.c
MatMatMultSymbolic_SeqDense_SeqDense in src/mat/impls/dense/seq/dense.c
MatMatMultSymbolic_Elemental in src/mat/impls/elemental/matelem.cxx
MatMatMultSymbolic_AIJ_AIJ_wHYPRE in src/mat/impls/hypre/mhypre.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages