[gmx-developers] BlueGene

[David van der Spoel]

Roland Schulz wrote:
> Hi,
> 
> it was mostly wrong names in the #include statements.
> 
> It works on BlueGene/P and is much faster than the C non-bonded kernel 
> (about 2x). With this intrinsic C kernel one gets 18% of peak. Because 
> BlueGene doesn't have SIMD commands specific for single precision (thus 
> it does only 2 at a time instead of 4) the performance difference to 
> Opteron is greater than for double precision code. The performance 
> difference to a Barcelona 2.1Ghz core is 5.7x (at 20% peak).

I'm not sure I follow you.
Are you saying the BlueGene/P core is 5.7 times faster than an Opteron core?
Or the other way around? And in single or in double?

> 
> Roland
> 
> On Wed, Jul 30, 2008 at 12:29 PM, Roland Schulz <roland at utk.edu 
> <mailto:roland at utk.edu>> wrote:
> 
>     Hi,
> 
>     it seems that the blugene non-bonded kernel in the CVS version is
>     incomplete. E.g. the nb_kernel_bluegene_test_asm.h is missing as far
>     as I can see. The gromacs wiki for bluegene explains how to get the
>     kernel generated by mknb to work. Also on the mailinglist all the
>     messages I found about BlueGene were about mknb and not abou the
>     bluegene specifik kernel.
> 
>     Could it be that it is incomplete do one has to do somethng to
>     generate these files?
> 
>     Roland
> 
> 
>     On Wed, Jul 30, 2008 at 11:45 AM, Berk Hess <hessb at mpip-mainz.mpg.de
>     <mailto:hessb at mpip-mainz.mpg.de>> wrote:
> 
>         Hi,
> 
>         Mathias Puetz from IBM wrote non-bonded kernels for BlueGene/L.
>         I don't know if these are also used for BlueGene/P.
>         If there are problems, he would be the person to contact.
> 
>         Berk.
> 
> 
>         Roland Schulz wrote:
> 
>             Hi,
> 
>             has someone looked at the non-bonded kernels for BlueGene/P?
>             Based on the assembler produced by the compiler, it does no
>             SIMD, runs out of registers and does unnecessary rounding.
> 
>             Are there plans for a PPC450 assembler kernel?
> 
>             Roland
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-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se
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