On Thu, 27 Sep 2007, Artur Tyliszczak wrote:
> I am not able to run a job in this way: mpirun n0,1,2,3 ./jobname on
> this computer.
What was the content of the hostfile that you passed to lamboot ?
> On the other hand if I want to run a job: mpirun c0,1,2,3 ./jobname
> I have to first boot the lam with lamboot hostfile, where in the
> hostfile I have: localhost cpu=16. Is it a correct procedure?
The procedure is correct. The usage of 'localhost' in the hostfile
makes sense only in the case where you want to use this one node for
the job; if you want to use processors from different nodes, you need
to use the real nodes names or their IPs.
> I run the job mpirun c0,1,2,3 ./jobname. Does it mean that I am
> using 2 cores from processor 0 and 2 cores from processor 1 ?
LAM/MPI doesn't have any idea about the hardware details of your
computers; if you want more control you should look at Open MPI.
When LAM/MPI launches more processes on a node to be part of the same
job (as you seem to try to), it's the OS kernel which decides where
these processes are run. Recent Linux distributions have tools to
inform the kernel about your preferences w.r.t. the placement of
processes on processors - however you should first understand all the
aspects (f.e. if you use more than one node, do you also need to bind
the network card to a certain processor ?) before starting to play
with them.
So, all your examples are going to end running in the same way - no
real ties between the process and the processor...
> In all above cases when I check the cpu usage by 'top' then I can
> see four cpu working at 100%. The time of computations is more or
> less the same in all cases.
... and that's the reason why all the results are the same.
> This is the case when I run the mpirun c0,0,0,0 ./jobname on PC with
> 1 dual core processor. Could you explain me this?
That's a total of 2 cores in that node. You are starting 4 processes
which compete for CPU time; each of them will get approximately 2/4 =
0.5 = 50%.
> Do you know any "proper build options for shared memory messaging"
> for one of those compilers?
It's more a matter of configuring LAM/MPI rather than using the
compilers in a special way. This along with other questions above lead
me to believe that you didn't read too much on the subject. There is
enough documentation and a FAQ for LAM/MPI which should explain most
of these issues - do read them.
--
Bogdan Costescu
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu_at_[hidden]
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