petsc-3.12.5 2020-03-29

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.

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