[MITgcm-devel] Re: [MITgcm-support] Question: boundary exchange, hrcube condfiguration

[Jean-Michel Campin]

Hi,

I think (but I might be wrong) that,
in the simplest case (a tile in the middle of a face),
we need a 1rst call to fill the halo region next to the tile edges
(i.e., [1-Olx:0,1:sNy]),
and a second call to fill the "corner" parts of the halo regions
(i.e, [1-Olx:0,1-Oly:0]).

This could be done in just 1 call, but would require to connect to 
8 tiles instead of only 4 in the present case.

I would be interesting to see how to apply the same solution
as with exch1 (or why it's not possible).

Now, I am trying to figure out why we need 3 exit2_rl2_cube calls ...

Jean-Michel

On Wed, Jun 27, 2007 at 01:44:54PM +0200, Martin Losch wrote:
> Hi there,
> 
> could someone please explain this to Michael (and me)? Why do we need  
> two calls to exch2_rl1_cube?
> 
> Martin
> 
> On 22 Jun 2007, at 14:14, Michael Schroeter wrote:
> 
> >Hi,
> >
> >as Martin already reported in an earlier posting
> >(http://forge.csail.mit.edu/pipermail/mitgcm-support/2007-March/ 
> >004719.html)
> >we have some unexpected scaling behaviour on a IBM p690
> >(cubed sphere configuration, 16 passive tracers).
> >
> >We found out that the boundary exchange of the ptracers data seems  
> >to be
> >responsible for the slow down of the code. Now we have some ideas for
> >code optimazation.
> >
> >However, there is one thing in the current code I do not unterstand.
> >In "exch2_3d_rl.F" the subroutine "EXCH2_RL1_CUBE" is called two times
> >with exactly the same values for the argument list parameters
> >(even if the cpp option "W2_FILL_NULL_REGIONS" is undefined).
> >Can anybody explain that to me?
> >
> >Thanks in advance.
> >
> >Regards
> >Michael
> >
> >-- 
> >Dr. Michael Schroeter                          Phone: +49(471) 
> >4831-2084
> >Email: Michael.Schroeter at awi.de                Fax:   +49(471) 
> >4831-1149
> >Alfred-Wegener-Institute for Polar- and Marine Research
> >Am Handelshafen 12, D-27570 Bremerhaven                       
> >www.awi.de
> >_______________________________________________
> >MITgcm-support mailing list
> >MITgcm-support at mitgcm.org
> >http://mitgcm.org/mailman/listinfo/mitgcm-support
> 
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-devel