MatLoad

Loads a matrix that has been stored in binary format with MatView(). The matrix format is determined from the options database. Generates a parallel MPI matrix if the communicator has more than one processor. The default matrix type is AIJ.

Synopsis

#include "mat.h"  
int MatLoad(Viewer viewer,MatType outtype,Mat *newmat)
Collective on Viewer

Input Parameters

viewer - binary file viewer, created with ViewerBinaryOpen()
outtype - type of matrix desired, for example MATSEQAIJ, MATMPIROWBS, etc. See types in petsc/include/mat.h.

Output Parameters

newmat -new matrix

Basic Options Database Keys

The following options will work if you first call MatGetTypeFromOptions() and pass the resulting type to MatLoad(). These options use MatCreateSeqXXX or MatCreateMPIXXX, depending on the communicator, comm.
-mat_aij - AIJ type
-mat_baij - block AIJ type
-mat_dense - dense type
-mat_bdiag - block diagonal type
-mat_complex - indicates the matrix has complex entries
-mat_double - indicates the matrix has double entries

More Options Database Keys

-mat_seqaij - AIJ type
-mat_mpiaij - parallel AIJ type
-mat_seqbaij - block AIJ type
-mat_mpibaij - parallel block AIJ type
-mat_seqbdiag - block diagonal type
-mat_mpibdiag - parallel block diagonal type
-mat_mpirowbs - parallel rowbs type
-mat_seqdense - dense type
-mat_mpidense - parallel dense type

More Options Database Keys

Used with block matrix formats (MATSEQBAIJ, MATMPIBDIAG, ...) to specify block size
-matload_block_size <bs> - Used to specify block diagonal numbers for MATSEQBDIAG and MATMPIBDIAG formats
-matload_bdiag_diags <s1,s2,s3,...> -

Notes

MatLoad() automatically loads into the options database any options given in the file filename.info where filename is the name of the file that was passed to the ViewerBinaryOpen(). The options in the info file will be ignored if you use the -matload_ignore_info option.

In parallel, each processor can load a subset of rows (or the entire matrix). This routine is especially useful when a large matrix is stored on disk and only part of it existsis desired on each processor. For example, a parallel solver may access only some of the rows from each processor. The algorithm used here reads relatively small blocks of data rather than reading the entire matrix and then subsetting it.

Notes for advanced users

Most users should not need to know the details of the binary storage format, since MatLoad() and MatView() completely hide these details. But for anyone who's interested, the standard binary matrix storage format is

   int    MAT_COOKIE
   int    number of rows
   int    number of columns
   int    total number of nonzeros
   int    *number nonzeros in each row
   int    *column indices of all nonzeros (starting index is zero)
   Scalar *values of all nonzeros

Note for Cray users, the int's stored in the binary file are 32 bit integers; not 64 as they are represented in the memory, so if you write your own routines to read/write these binary files from the Cray you need to adjust the integer sizes that you read in, see PetscReadBinary() and PetscWriteBinary() to see how this may be done.

In addition, PETSc automatically does the byte swapping for machines that store the bytes reversed, e.g. DEC alpha, freebsd, linux, nt and the paragon; thus if you write your own binary read/write routines you have to swap the bytes; see PetscReadBinary() and PetscWriteBinary() to see how this may be done.

Keywords

matrix, load, binary, input

See Also

ViewerBinaryOpen(), MatView(), VecLoad(), MatLoadRegister(),
MatLoadRegisterAll(), MatGetTypeFromOptions()

Examples

src/mat/examples/tutorials/ex1.c
src/sles/examples/tutorials/ex10.c

Level:beginner
Location:src/mat/utils/matio.c
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