[petsc-users] structure of A

[Barry Smith]

> On Dec 16, 2016, at 8:17 PM, Massoud Rezavand <msdrezavand at gmail.com> wrote:
> 
> Dear PETSc team,
> 
> Sorry if my question is more related to math. 
> Using PETSc, how important is the structure of the matrix A for performance? I mean mainly the diagonal and off-diagonal parts.
> 
> For example, solving with a matrix which is dense in diagonal part and sparse in off-diagonal part is faster than with a matrix in which the non-zeros are distributed randomly?

  Yes, loosely speaking this is true. More technically there is a term "diagonally dominate", or block diagonally dominate, for those matrices generally iterative methods perform better.

   Barry


> 
> Thanks in advance.
> 
> Massoud