[petsc-users] EPS iteration number

[Jose E. Roman]

> El 16/9/2015, a las 21:09, Xujun Zhao <xzhao99 at gmail.com> escribió:
> 
> Hi all,
> 
> I am solving a max/min eigenvalue problem, and call EPSGetIterationNumber() to get the iteration number for convergence. However, it always returns 1. This is a little confused, because I can see my subroutine of MATOP_MULT operation has been called 6 or 16 times with different configurations.
> 
> The ConvergedReason returns 2, so it looks like the eigenvalue is correct. 
> also, it shows
>  1 EPS nconv=2 first unconverged value (error) 0.0158234 (2.15550644e-03)
> 
> what does it mean?
> 
> Thanks.
> 
> Xujun

In EPS the iteration number refers to “outer” iterations, that is, restarts. So in Krylov-Schur with ncv=16 the first outer iteration will perform 16 MatMult’s and in subsequent outer iterations it will perform 8 MatMult’s.

Jose