[MITgcm-devel] cs510 on IBM p690

[Martin Losch]

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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