#include "petscmat.h" PetscErrorCode MatMatMultSymbolic(Mat A,Mat B,PetscReal fill,Mat *C)Neighbor-wise Collective on Mat

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 |

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, http://arxiv.org/abs/1006.4173 We should incorporate them into PETSc.

** Level:intermediate
Location:**src/mat/interface/matrix.c

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