[gmx-users] Pme on gpu performance

[Szilárd Páll]

Dear Rafael,

It really depends on the processors, GPUs, as well as whether you are
interested in performance or performance/buck. Also note, that with
GPUs you'll need considerably more atoms/core.

First of all, the E7-s are 8-core processors, so four of them is only
32 (and from what I can see it doesn't have HT). Moreover, they cost a
whopping ~2500 USD each. In contrast a pair of Westmares go for the
about price of one E7 (some less) and then you can get Teslas
(although these cost quite a lot) or even GF GTX580-s -- which by the
way are ~30-40% faster and 4-5x cheaper. With two GPUs you will
probably not match the 4xE7 performance -- maybe with GTX580s --, but
with 3-4 you probably will.

However, you might want to look at AMD-based servers as well, they
have *really* good performance/price ratio, so when it comes to
ns/day/$ dual-/quad-socket AMD machines can get close to Westmere+GPU
combination, but not quad-socket Intels can't.

One last tip: unless you really need so compute power in one single
machine, you can also consider the budget option of getting desktop
Sandy bridge with say two budget-ish GF cards (e.g. 570/560 Ti) and
you'll have an entire box with everything below 1000 USD.

Regards,
--
Szilárd

PS: I hope you don't mind the USD prices, it was easier to google
those than EUR ones.

On Tue, Nov 29, 2011 at 10:14 PM,  <rafapa at us.es> wrote:
> Dear Szilárd,
> now 64 cores machines are available, for instance, using Xeons E7-8837. Do
> you have any idea about which combination will give more performance? I
> mean, 64 CPU cores or 16-32 CPU cores + 4 C2075 or similar. The limit of 4
> GPUs is imposed by the MB of the machine I have in mind.
>
> Thanks for the information.
>
> Sincerely,
> Dr. Rafael R. Pappalardo
> Dept. Quimica Fisica, Univ. de Sevilla (Spain)
>
> On Tue, 29 Nov 2011 22:04:08 +0100, Szilárd Páll wrote:
>>
>> Hi Andrzej,
>>
>>> One more question: will a ratio of gpu/cpu units and cores be of
>>> importance
>>> in next gromacs releases ? at the moment the code uses one core per gpu
>>> unit, wright ? When the code is gpu parallel how can this change ?
>>
>> Yes, it will. We use both CPU & GPU and load balance between them. For
>> optimal performance you'll want up to 4-8 cores/GPU, but ultimately it
>> depends on the performance of each.
>>
>> --
>> Szilárd
>>
>>
>>> Thank you
>>>
>>> Andrzej
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