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

A | - the left matrix | |

B | - the right matrix | |

scall | - either MAT_INITIAL_MATRIX or MAT_REUSE_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 the result is a dense matrix this is irrelevent |

MAT_REUSE_MATRIX can only be used if the matrices A and B have the same nonzero pattern as in the previous call and C was obtained from a previous call to this function with either MAT_INITIAL_MATRIX or MatMatMultSymbolic()

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

If you have many matrices with the same non-zero structure to multiply, you should either

1) use MAT_REUSE_MATRIX in all calls but the first or

2) call MatMatMultSymbolic() once and then MatMatMultNumeric() for each product neededIn the special case where matrix B (and hence C) are dense you can create the correctly sized matrix C yourself and then call this routine with MAT_REUSE_MATRIX, rather than first having MatMatMult() create it for you. You can NEVER do this if the matrix C is sparse.

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

Index of all Mat routines

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