[petsc-users] chelosky vs multigrid

[Jed Brown]

Fazlul Huq <huq2090 at gmail.com> writes:

> Thanks.
>
> I have tried with large problem also (10^7 X 10^7). Even then I got
> cholesky faster than multigrid.
> But, the problem is 1D. May be that's the reason.

Exactly.  Cholesky is O(n) with a very small constant in 1D, O(n^{3/2})
in 2D, and O(n^2) in 3D.