# MatCreateDense#

Creates a matrix in MATDENSE format.

## Synopsis#

#include "petscmat.h"
PetscErrorCode MatCreateDense(MPI_Comm comm, PetscInt m, PetscInt n, PetscInt M, PetscInt N, PetscScalar *data, Mat *A)


Collective

## Input Parameters#

• comm - MPI communicator

• m - number of local rows (or PETSC_DECIDE to have calculated if M is given)

• n - number of local columns (or PETSC_DECIDE to have calculated if N is given)

• M - number of global rows (or PETSC_DECIDE to have calculated if m is given)

• N - number of global columns (or PETSC_DECIDE to have calculated if n is given)

• data - optional location of matrix data. Set data to NULL (PETSC_NULL_SCALAR for Fortran users) for PETSc to control all matrix memory allocation.

## Output Parameter#

• A - the matrix

## Notes#

The dense format is fully compatible with standard Fortran 77 storage by columns.

Although local portions of the matrix are stored in column-major order, the matrix is partitioned across MPI ranks by row.

The data input variable is intended primarily for Fortran programmers who wish to allocate their own matrix memory space. Most users should set data=NULL (PETSC_NULL_SCALAR for Fortran users).

The user MUST specify either the local or global matrix dimensions (possibly both).

MATDENSE, MatCreate(), MatCreateSeqDense(), MatSetValues()

intermediate

## Location#

src/mat/impls/dense/mpi/mpidense.c

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