preallocate space

[Yixun Liu]

Hi,
In ex2,
ierr = MatMPIAIJSetPreallocation(A,5,PETSC_NULL,5,PETSC_NULL);CHKERRQ(ierr);
ierr = MatSeqAIJSetPreallocation(A,5,PETSC_NULL);CHKERRQ(ierr);

It means that two spaces are allocated for matrix A?

Thanks.