MatMatMult#
Performs matrix-matrix multiplication C=A*B.
Synopsis#
#include "petscmat.h"
PetscErrorCode MatMatMult(Mat A, Mat B, MatReuse scall, PetscReal fill, Mat *C)
Neighbor-wise Collective
Input Parameters#
A - the left matrix
B - the right matrix
scall - either
MAT_INITIAL_MATRIX
orMAT_REUSE_MATRIX
fill - expected fill as ratio of nnz(C)/(nnz(A) + nnz(B)), use
PETSC_DETERMINE
orPETSC_CURRENT
if you do not have a good estimate if the result is a dense matrix this is irrelevant
Output Parameter#
C - the product matrix
Notes#
Unless scall is MAT_REUSE_MATRIX
C will be created.
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 MAT_INITIAL_MATRIX
.
To determine the correct fill value, run with -info
and search for the string “Fill ratio” to see the value actually needed.
In 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.
The deprecated PETSC_DEFAULT
in fill
also means use the current value
Example of Usage#
MatProductCreate(A,B,NULL,&C);
MatProductSetType(C,MATPRODUCT_AB);
MatProductSymbolic(C);
MatProductNumeric(C); // compute C=A * B
MatProductReplaceMats(A1,B1,NULL,C); // compute C=A1 * B1
MatProductNumeric(C);
MatProductReplaceMats(A2,NULL,NULL,C); // compute C=A2 * B1
MatProductNumeric(C);
See Also#
Matrices, Mat
, MatProductType
, MATPRODUCT_AB
, MatTransposeMatMult()
, MatMatTransposeMult()
, MatPtAP()
, MatProductCreate()
, MatProductSymbolic()
, MatProductReplaceMats()
, MatProductNumeric()
Level#
intermediate
Location#
Examples#
src/snes/tutorials/ex70.c
src/ksp/ksp/tutorials/ex27.c
src/tao/pde_constrained/tutorials/elliptic.c
src/ksp/pc/tutorials/ex4.c
src/tao/pde_constrained/tutorials/parabolic.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages