#include "petscmat.h" PetscErrorCode MatMatMatMult(Mat A,Mat B,Mat C,MatReuse scall,PetscReal fill,Mat *D)Neighbor-wise Collective on Mat
| A | - the left matrix | |
| B | - the middle matrix | |
| C | - the right matrix | |
| scall | - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX | |
| fill | - expected fill as ratio of nnz(D)/(nnz(A) + nnz(B)+nnz(C)), 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, B and C have the same nonzero pattern as in the previous call
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 use MAT_REUSE_MATRIX in all calls but the first or