petsc-3.12.5 2020-03-29

MatCreateComposite

Creates a matrix as the sum or product of one or more matrices

#include "petscmat.h" 
PetscErrorCode MatCreateComposite(MPI_Comm comm,PetscInt nmat,const Mat *mats,Mat *mat)

Collective

mat -the matrix

	-mat_composite_merge	- merge in MatAssemblyEnd()
	-mat_composite_merge_mvctx	- merge Mvctx of component matrices to optimize communication in MatMult() for ADDITIVE matrices
	-mat_composite_merge_type	- set merge direction

Alternative construction

      MatCreate(comm,&mat);

      MatSetSizes(mat,m,n,M,N);

      MatSetType(mat,MATCOMPOSITE);

      MatCompositeAddMat(mat,mats[0]);

      ....

      MatCompositeAddMat(mat,mats[nmat-1]);

      MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);

      MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);

For the multiplicative form the product is mat[nmat-1]*mat[nmat-2]*....*mat[0]

advanced