MatCreateSum

Creates a matrix as the implicit sum of zero or more matrices. This class is an adoption of MATCOMPOSITE type in PETSc.

PetscErrorCode  MatCreateSum(MPI_Comm comm,PetscInt nmat,const Mat *mats,Mat *mat)

Collective on MPI_Comm

A -the matrix

Alternative construction

      MatCreate(comm,&mat);

      MatSetType(mat,MATSUM);

      MatCompositeAddMat(mat,mats[0]);

      ....

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

      MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);

      MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);