[mpich-discuss] MPICH v1.2.7p1 and SMP clusters

[Gustavo Miranda Teixeira]

I'm sorry, i should have said that in the first message. They are all Intel
Xeon 1.6GHz with 4MB cache L2


On Tue, Jan 13, 2009 at 3:54 PM, chong tan <chong_guan_tan at yahoo.com> wrote:

> what are the CPU on these 2 boxes ?
>
> tan
>
>
> --- On *Tue, 1/13/09, Gustavo Miranda Teixeira <magusbr at gmail.com>* wrote:
>
> From: Gustavo Miranda Teixeira <magusbr at gmail.com>
> Subject: Re: [mpich-discuss] MPICH v1.2.7p1 and SMP clusters
> To: mpich-discuss at mcs.anl.gov
> Date: Tuesday, January 13, 2009, 9:37 AM
>
>
> Hello Marcus,
>
> I can't see what your point is. Do you want to know in which core is the
> processes allocated? Like if it's on the same processor or different ones?
>
>
> On Tue, Jan 13, 2009 at 3:06 PM, Marcus Vinicius Brandão Soares <
> mvbsoares at gmail.com> wrote:
>
>> Hello Gustavo and all,
>>
>> You described that you are using two machines with a dual processor in
>> each one. If I can model it in a simple graph, we have two vertices and two
>> unidirectional edges.
>>
>> Each machine has a dual processor, each one with dual core, so there are 8
>> processor. But lets think again in the graph model: now we have two
>> vertices, each one with two more vertices; these last two vertices have two
>> more vertices too, and so this is the end.
>>
>> Do you know the structure of the communication lines of the core
>> processors ?
>>
>> 2009/1/13 Gustavo Miranda Teixeira <magusbr at gmail.com>
>>
>> Hello everyone!
>>>
>>> I've been experiencing some issues when using MPICH v1.2.7p1 and a SMP
>>> cluster and thought maybe some one can help me here.
>>>
>>> I have a small cluster with two dual processor machines with gigabit
>>> ethernet communication. Each processor is a dual core which sums up to 8
>>> cores of processors. When I run an application spreading 4 processes in both
>>> the machines (like distributing 2 processes in one machine and 2 processes
>>> in another) I get a significantly better performance than when I run the
>>> same application using 4 processes in only one machine. Isn`t it a bit
>>> curious? I know some people who also noticed that, but no one can explain me
>>> why this happens. Googling it didn't helped either. I originally thought it
>>> was a problem from my kind of application (a heart simulator which using
>>> PETSc to solve some differential equations) but some simple experimentations
>>> showed a simple MPI_Send inside a huge loop causes the same issue. Measuring
>>> cache hits and misses showed it`s not a memory contention problem. I also
>>> know that a in-node communication in MPICH uses the loopback interface, but
>>> as far as I know a message that uses loopback interface simply takes a
>>> shortcut to the input queue instead of being sent to the device, so there is
>>> no reason for the message to take longer to get to the other processes. So,
>>> I have no idea why it`s taking longer to use MPICH in the same machine. Does
>>> anyone else have noticed that too? Is there some logical explanation for
>>> this to happen?
>>>
>>> Thanks,
>>> Gustavo Miranda Teixeira
>>>
>>
>>
>>
>> --
>> Marcus Vinicius
>> --
>> "Havendo suficientes colaboradores,
>> Qualquer problema é passível de solução"
>> Eric S. Raymond
>> A Catedral e o Bazar
>>
>> "O passado é apenas um recurso para o presente"
>> Clave de Clau
>>
>> "Ninguém é tão pobre que não possa dar um abraço; e
>> Ninguém é tão rico que não necessite de um abraço.
>> Anônimo
>>
>
>
>
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