[petsc-users] SNESVI convergence spped

[Ataollah Mesgarnejad]

Barry,

There are two sets of output for both virs and viss. Slow convergence aside I can't see why line search fails after we hit lower bound at some nodes? I tried quadratic and cubic line search both and got the same result. 

Best,
Ata

On Jan 26, 2012, at 9:07 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

> 
>   Don't even touch VISS, focus on RS.  What solver did you use in the run you sent the output for? 
> 
>   *  If SS please rerun (with -snes_monitor) with RS and send the output again.
> 
>   * If RS then it is very puzzling that you get that slow convergence since the number of active constraints does not change so it should converge just like plain old Newton.
> 
>   Barry
> 
> 
> 
> On Jan 25, 2012, at 8:55 AM, Ataollah Mesgarnejad wrote:
> 
>> Barry,
>> 
>> Here is my output from my program  with petsc-dev (txt files attached). Even with petsc-dev (revision 21929), SNES (I tried VISS and VIRS) takes a long time to converge (>50 iterations) from a small problem (99 HEX20 elements, 681 DOFs for SNES). The exodusII output files are uploaded in the link; I attached pictures of last time step for Psi field which we solve with SNESVI and u field which the displacement in the x-direction and is my loading.  As it was the case with petsc-3.2 line search diverges as soon as we hit the lower bound in a neighborhood of nodes. I ran with KSPPREONLY and PCLU to exclude possibility of LS failure because of the KSP tol.
>> 
>> Best,
>> Ata
>> 
>> link to exodusII files: http://cl.ly/0g431o443v240x1h2h1B
>> 
>> <output-viss.txt><axial-tension-virs-u.png><axial-tension-virs-psi.png><axial-tension-viss-psi.png><axial-tension-viss-u.png><output-virs.txt>
>