[MITgcm-devel] cs510 on IBM p690

[chris hill]

Dimitris/Martin,

  Dimitris - If you are bored with nothing to do today, can you do a 27 
CPU test on columbia. I have to go over to Brigham and Women's with 
Helen today, so I can't do it until this evening.

  Martin - Can try a run with the CPP flag
    W2_USE_E2_SAFEMODE
  set (in W2_OPTIONS.h, it may be set already depending on the 
W2_OPTIONS.h you are using)
  and maybe even
  W2_E2_DEBUG_ON
  (but that generates lots of output).

Chris
Martin Losch wrote:
> Hi Dimitris,
> 
> "Soccer ball" was my first association, too.
> 
> I use Olx=Oly=4. (see SIZE.h)
> 
> I don't use 27 tiles, but 27 CPUs. I use 216 tiles (it's your s216_85x85 
> directory, but I have modified SIZE.h_54 to run on nPx=27 instead of 54 
> CPUs, increasing nSx to 8, 8x27=216), so each block is 6 tiles. But 
> clever as you are, you immediatley spotted that it is only the exchange 
> in the j-direction, that is the problem (it took me a whole day to 
> figure that out). And to give you even more information, this problem 
> does NOT show up in Theta/Salt, but only in U and V (and consequently in 
> Eta), in the first time step. And it's only the j/y-direction that's 
> strange. So I suspect something wrong in the exch_uv_* and/or exch2_uv_*
> 
> So, what can go wrong in the exchanges j-direction, that is specific to 
> IBM p690 (and xlf-compilers), and shows only up in this particular 
> configuration so far (the cs32 does not have these stripes, I tried 4 
> tiles per face = 24 tiles)?
> 
> Martin
> 
> On 13 Feb 2007, at 23:57, Dimitris Menemenlis wrote:
> 
>> Martin, that's a very nice design for next world cup soccer ball.
>>
>> One thing I find strange is that your figure has 36 rather than 27 
>> tiles?  Are you sure that you used the attached SIZE.h file.  And if 
>> not did you have
>>
>>      &           OLx =   4,
>>      &           OLy =   4,
>>
>> D.
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