[MITgcm-devel] do we need exch_z ?

[Chris Hill]

JM,

 I have started looking into this. However, I have run into a weird prob on
one processor for which I need your ace detective skills. If I set OL=3 for
either aim_5l.cs or global_ocean.cs and use exch_z the run crashes. Do you
see anything like this (on one proc)? I'm using ifc.

Chris 

> -----Original Message-----
> From: mitgcm-devel-bounces at mitgcm.org 
> [mailto:mitgcm-devel-bounces at mitgcm.org] On Behalf Of 
> Jean-Michel Campin
> Sent: Tuesday, February 24, 2004 7:39 PM
> To: MITgcm-devel at mitgcm.org
> Subject: [MITgcm-devel] do we need exch_z ?
> 
> Hi,
> 
> Here is what I found, trying to run cs-32x32 on 6 cpu:
> 
> a) presently, there is no exch_Z in pkg/exch2 but 
> ini_curvilinear_grid.F call 3 times exch_Z (for xG, yG, and 
> rAz) The consequence is that the exch1 version of exch_Z 
> (eesupp/src) is used instead, which is fine on 1 processor 
> but make the model blowing up after 2 iterations when trying on 6 cpu.
> 
> b) if I comment out the 3 calls to exch_Z, aim.5l_cs produces 
> identical results on 1 and 6 cpu.
> 
> But the problem is that rAz, xG, yG (and fCoriG) and no 
> longer valid outside (1:sNx+1,1:sNy+1). This is likely to 
> cause problems with high-order momentum advection (VI form) 
> and high-order viscosity. (Alistair, can you confirm ?).
> 
> c) I had a quick look at
> MITgcm_contrib/high_res_cube/code-mods/ini_curvilinear_grid.F
> and did not see any call to exch_Z.
> Is it possible that rAz is set to zero outside of (1:sNx+1,1:sNy+1) ?
> and has some effect on the blowing up at the edgde of the cube ?
> 
> Jean-Michel
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