[petsc-users] Convergence behavior of different solvers

[Alexander Grayver]

Hello,

Plotting values of relative residual norm versus iteration I noticed 
that these curves have different behavior. For instance, ones I got with 
BiCGStab are oscillatory and rather noisy with large jumps within few 
iterations. Curves for QMR are smooth, however it's usual that they 
stagnate for ~10-20 iterations and then go down further. Same 
preconditioner is applied for both and both methods are Lanczos based, 
so I don't understand this.
I'm wondering is this just my specific case or there is general 
explanation for that?

-- 
Regards,
Alexander