MatGetInfo#

Returns information about matrix storage (number of nonzeros, memory, etc.).

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatGetInfo(Mat mat, MatInfoType flag, MatInfo *info)

Collective if MAT_GLOBAL_MAX or MAT_GLOBAL_SUM is used as the flag

Input Parameters#

mat - the matrix
flag - flag indicating the type of parameters to be returned (MAT_LOCAL - local matrix, MAT_GLOBAL_MAX - maximum over all processors, MAT_GLOBAL_SUM - sum over all processors)

Output Parameter#

info - matrix information context

Options Database Key#

-mat_view ::ascii_info - print matrix info to PETSC_STDOUT

Notes#

The MatInfo context contains a variety of matrix data, including number of nonzeros allocated and used, number of mallocs during matrix assembly, etc. Additional information for factored matrices is provided (such as the fill ratio, number of mallocs during factorization, etc.).

Example#

See the file ${PETSC_DIR}/include/petscmat.h for a complete list of data within the MatInfo context. For example,

      MatInfo info;
      Mat     A;
      double  mal, nz_a, nz_u;

      MatGetInfo(A, MAT_LOCAL, &info);
      mal  = info.mallocs;
      nz_a = info.nz_allocated;

Fortran users should declare info as a double precision array of dimension MAT_INFO_SIZE, and then extract the parameters of interest. See the file ${PETSC_DIR}/include/petsc/finclude/petscmat.h a complete list of parameter names.

      double  precision info(MAT_INFO_SIZE)
      double  precision mal, nz_a
      Mat     A
      integer ierr

      call MatGetInfo(A, MAT_LOCAL, info, ierr)
      mal = info(MAT_INFO_MALLOCS)
      nz_a = info(MAT_INFO_NZ_ALLOCATED)