Putting a peculiar multilevel scheme into DMMG?

Barry Smith bsmith at mcs.anl.gov
Sun Dec 13 12:01:39 CST 2009

On Dec 13, 2009, at 11:43 AM, Jed Brown wrote:

> On Sun, 13 Dec 2009 10:11:07 -0600, Matthew Knepley  
> <knepley at gmail.com> wrote:
>> Not sure if you would need API additions. Can't everything you  
>> describe be
>> handled through defining the grid, operator, residual, and  
>> projections?
> Yes, but DMMG doesn't seem to have an API for setting such things.

    Hmm, doesn't the DMMG make calls on the DM to get those operators?  
So you would provide a DM that provided the custom beasts you want?

    Or is it that the DMMG doesn't have enough of them? That is, it  
does not have a separate function for restriction, for interpolation,  
for residual computer?

    Regarding how I see DMMG and PCMG. PCMG has the "function slots"  
for what MG needs. DMMG calls methods on the DM to "fill" those  
function slots. The problem is that DMMG is not a PC, so cannot be  
imbedded inside a larger solve; for example wanting to use DMMG on two  
components of that three component problem.  My thought was that we  
would move the "filling" behavior of DMMG directly into PCMG (or PC?)  
so that a PCMG has both the "function slots" one can fill manually as  
today or one can provide a DM and the PCMG would use methods on the DM  
to fill up its own "function slots". It is actually a simpler model  
than today with the DMMG and more flexible since the DMMG  
functionality could be used anywhere in a big hierarchy of  
pcfieldsplit, pccomposite, pcmg etc. Now if I could stop sleeping 10  
hours a day and wasting most of my awake time on anxiety I could do  
all this cool shit.


> does, and it was the interface I initially thought to use.
> Jed

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