petsc-3.7.1 2016-05-15
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# MatMPIAIJSetPreallocationCSR

Allocates memory for a sparse parallel matrix in AIJ format (the default parallel PETSc format).

### Synopsis

    #include "petscmat.h"
    PetscErrorCode  MatMPIAIJSetPreallocationCSR(Mat B,const PetscInt i[],const PetscInt j[], const PetscScalar v[])

Collective on MPI_Comm Many br

### Input Parameters

| B | - the matrix Many br
| i | - the indices into j for the start of each local row (starts with zero) Many br
| j | - the column indices for each local row (starts with zero) Many br
| v | - optional values in the matrix Many br

Many br

### Notes

The i, j, and a arrays ARE copied by this routine into the internal format used by PETSc; Many brthus you CANNOT change the matrix entries by changing the values of a[] after you have Many brcalled this routine. Use MatCreateMPIAIJWithSplitArrays() to avoid needing to copy the arrays. Many br

The i and j indices are 0 based, and i indices are indices corresponding to the local j array. Many br

The format which is used for the sparse matrix input, is equivalent to a Many brrow-major ordering.. i.e for the following matrix, the input data expected is Many bras shown Many br

           1 0 0

           2 0 3     P0

          -------

           4 5 6     P1

        Process0 [P0]: rows_owned=[0,1]

           i =  {0,1,3}  [size = nrow+1  = 2+1]

           j =  {0,0,2}  [size = 3]

           v =  {1,2,3}  [size = 3]

        Process1 [P1]: rows_owned=[2]

           i =  {0,3}    [size = nrow+1  = 1+1]

           j =  {0,1,2}  [size = 3]

           v =  {4,5,6}  [size = 3]

### Keywords

matrix, aij, compressed row, sparse, parallel

### See Also

MatCreate(), MatCreateSeqAIJ(), MatSetValues(), MatMPIAIJSetPreallocation(), MatCreateAIJ(), MPIAIJ,
MatCreateSeqAIJWithArrays(), MatCreateMPIAIJWithSplitArrays() Many br

Level:developer
Location:src/mat/impls/aij/mpi/mpiaij.c
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