MatMPIAIJGetLocalMat

Creates a MATSEQAIJ from a MATMPIAIJ matrix.

Synopsis

#include "petscmat.h" 
PetscErrorCode MatMPIAIJGetLocalMat(Mat A, MatReuse scall, Mat *A_loc)

Not Collective

Input Parameters

• A - the matrix

• scall - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX

Output Parameter

• A_loc - the local sequential matrix generated

Notes

The matrix is created by taking all A’s local rows and putting them into a sequential matrix with mlocal rows and n columns.mlocal is the row count obtained with MatGetLocalSize() and n is the global column count obtained with MatGetSize().

In other words combines the two parts of a parallel MATMPIAIJ matrix on each process to a single matrix.

When A is sequential and MAT_INITIAL_MATRIX is requested, the matrix returned is the diagonal part of A (which contains the entire matrix), with its reference count increased by one. Hence changing values of A_loc changes A. If MAT_REUSE_MATRIX is requested on a sequential matrix then MatCopy(Adiag,*A_loc,SAME_NONZERO_PATTERN) is called to fill A_loc. Thus one can preallocate the appropriate sequential matrix A_loc and then call this routine with MAT_REUSE_MATRIX. In this case, one can modify the values of A_loc without affecting the original sequential matrix.

See Also

Matrices, Mat, MATMPIAIJ, MatGetOwnershipRange(), MatMPIAIJGetLocalMatCondensed(), MatMPIAIJGetLocalMatMerge()

Level

developer

Location

src/mat/impls/aij/mpi/mpiaij.c

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