MatSeqBAIJSetPreallocation
Sets the block size and expected nonzeros per row in the matrix. For good matrix assembly performance the user should preallocate the matrix storage by setting the parameter nz (or the array nnz). By setting these parameters accurately, performance during matrix assembly can be increased by more than a factor of 50.
Synopsis
#include "petscmat.h"
int MatSeqBAIJSetPreallocation(Mat B,int bs,int nz,int *nnz)
Collective on MPI_Comm
Input Parameters
| A | - the matrix
|
| bs | - size of block
|
| nz | - number of block nonzeros per block row (same for all rows)
|
| nnz | - array containing the number of block nonzeros in the various block rows
(possibly different for each block row) or PETSC_NULL
|
Options Database Keys
-mat_no_unroll -uses code that does not unroll the loops in the
block calculations (much slower)
-mat_block_size -size of the blocks to use
Notes
The block AIJ format is fully compatible with standard Fortran 77
storage. That is, the stored row and column indices can begin at
either one (as in Fortran) or zero. See the users' manual for details.
Specify the preallocated storage with either nz or nnz (not both).
Set nz=PETSC_DEFAULT and nnz=PETSC_NULL for PETSc to control dynamic memory
allocation. For additional details, see the users manual chapter on
matrices.
See Also
MatCreate(), MatCreateSeqAIJ(), MatSetValues(), MatCreateMPIBAIJ()
Level:intermediate
Location:src/mat/impls/baij/seq/baij.c
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