[petsc-dev] [petsc-users] Convergence of AMG

[Smith, Barry F.]

   Great, I just didn't understand the name. 

> On Oct 29, 2018, at 3:30 PM, Mark Adams <mfadams at lbl.gov> wrote:
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> 
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> On Mon, Oct 29, 2018 at 2:35 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
> 
>    Why not just stop it once it is equal to or less than the minimum values set by the person.
> 
> That is what it does now. It stops when it is below the value given.
>  
> Thus you need not "backtrack" by removing levels but the user still has some control over preventing a "tiny" coarse problem. For example in this case if the user set a minimum of 1000 it would end up with 642 unknowns on the coarse level
> 
> Yes, that is what it would do now. I thought you wanted something different.
>  
> which is likely better than 6 or 54.
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>  
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>     Barry
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> 
> > On Oct 29, 2018, at 8:27 AM, Mark Adams <mfadams at lbl.gov> wrote:
> > 
> > 
> > 
> > On Sun, Oct 28, 2018 at 4:54 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
> > 
> >    Moved a question not needed in the public discussions to petsc-dev to ask Mark.
> > 
> > 
> >    Mark,
> > 
> >     PCGAMGSetCoarseEqLim - Set maximum number of equations on coarsest grid 
> > 
> >    Is there a way to set the minimum number of equations on the coarse grid also? This particular case goes down to 6, 54 and 642 unknowns on the coarsest grids when I'm guessing it would be better to stop at 642 unknowns for the coarsest level. 
> > 
> > No, because I don't know how it is going to coarsen I did not want to bother with backtracking (I do when there is an error on the coarse grid so it would be easy to add this but I don't think it is worth the clutter). 
> > 
>