[petsc-users] SNESVI convergence spped

[Barry Smith]

   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>