On Thu, Sep 13, 2012 at 4:09 PM, Roy Stogner <[email protected]> wrote: > > On Thu, 13 Sep 2012, Derek Gaston wrote: > >> I haven't looked at that problem and don't know much about curl-curl >> spaces... but if the matrix would respond to multigrid at all I highly >> recommend compiling PETSc with Hypre support and using: >> -pc_type hypre -pc_hypre_type boomeramg >> >> For problems where it works it can't be beat... > > "Where it works" is the tricky part. It seems to fly on the curl-curl > problem, which is great; it failed to converge on a navier-stokes > problem I just tried, which rules it out as a default LIBMESH_OPTIONS > for me but still makes it a reasonable candidate for further > consideration... > > except that the very *first* time I tried PETSc with boomeramg, like 5 > years ago, it was "converging" to inaccurate answers on some of the > runs I tried. I'm 99% sure they'll have fixed whatever was wrong by > now, but once bitten twice shy...
You get the wrong solution with boomeramg on Stokes or Navier-Stokes because the preconditioner is singular. Try passing -ksp_monitor_true_residual when you run that way, and you'll see that it's not really converging. Original thread here: http://permalink.gmane.org/gmane.comp.mathematics.libmesh.user/2187 -- John ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
