[gmx-developers] BlueGene

[Roland Schulz]

Hi,

sorry for writing it confusing. One BlueGene core is 5.7x slower than one
Barcelona core.


Barcelona PPC450  Perfomance 3.3 0.6  Peak 16.8 3.4
The Performance is measured in both cases by taking the counted force Gflop
divided by the measured time in the Force part. So it is the force only
Gflop/s rate.


Roland

On Thu, Jul 31, 2008 at 2:15 AM, David van der Spoel
<spoel at xray.bmc.uu.se>wrote:

> 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
>>            This email was Anti Virus checked by Astaro Security
>>            Gateway. http://www.astaro.com
>>
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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
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