Not in Linux, I'm afraid - you can assign one process to a set of
cores, but Linux doesn't track individual threads.
If you look at OMPI 1.3's man page for mpirun, you'll see some info on
the rank-file mapping. Most of what was done is aimed at the use of
hostfiles where you specify the socket/core(s) to be used for each
rank. You can also provide a socket/core specification on the cmd
line, but I've been looking to see if you can specify something like
"the lowest rank on each node uses cores 1-4, next rank on each node
uses cores 5-8, ...".
I'm not sure the syntax is currently flexible enough for that (and the
people who would know haven't answered my inquiry), but if there is
interest, I imagine it could be expanded to support such specifications.
Ralph
On Nov 20, 2008, at 12:53 AM, Gabriele Fatigati wrote:
Is there a way to assign one thread to one core? Also from code, not
necessary with OpenMPI option.
Thanks.
2008/11/19 Stephen Wornom <stephen.wor...@sophia.inria.fr>:
Gabriele Fatigati wrote:
Ok,
but in Ompi 1.3 how can i enable it?
This may not be relevant, but I could not get a hybrid mpi+OpenMP
code to
work correctly.
Would my problem be related to Gabriele's and perhaps fixed in
openmpi 1.3?
Stephen
2008/11/18 Ralph Castain <r...@lanl.gov>:
I am afraid it is only available in 1.3 - we didn't backport it
to the
1.2
series
On Nov 18, 2008, at 10:06 AM, Gabriele Fatigati wrote:
Hi,
how can i set "slot mapping" as you told me? With TASK GEOMETRY?
Or is
a new 1.3 OpenMPI feature?
Thanks.
2008/11/18 Ralph Castain <r...@lanl.gov>:
Unfortunately, paffinity doesn't know anything about assigning
threads
to
cores. This is actually a behavior of Linux, which only allows
paffinity
to
be set at the process level. So, when you set paffinity on a
process,
you
bind all threads of that process to the specified core(s). You
cannot
specify that a thread be given a specific core.
In this case, your two threads/process are sharing the same
core and
thus
contending for it. As you'd expect in that situation, one
thread gets
the
vast majority of the attention, while the other thread is
mostly idle.
If you can upgrade to the beta 1.3 release, try using the slot
mapping
to
assign multiple cores to each process. This will ensure that the
threads
for
that process have exclusive access to those cores, but will not
bind a
particular thread to one core - the threads can "move around"
across
the
specified set of cores. Your threads will then be able to run
without
interfering with each other.
Ralph
On Nov 18, 2008, at 9:18 AM, Gabriele Fatigati wrote:
Dear OpenMPI developers,
i have a strange problem with mixed program MPI+OPENMP over
OpenMPI
1.2.6. I'm using PJL TASK GEOMETRY in LSF Scheduler, setting
2 MPI
process every compute node, and 2 OMP threads per process. Using
paffinity and maffinity, i've noted that over every node, i
have 2
thread that works 100%, and 2 threads doesn't works, or works
very
few.
If i disable paffinity and maffinity, 4 threads works well,
without
load imbalance.
I don't understand this issue: paffinity and maffinity should
map
every thread over a specific core, optimizing the cache flow,
but i
have this without settings there!
Can i use paffinity and maffinity in mixed MPI+OpenMP program?
Or it
works only over MPI thread?
Thanks in advance.
--
Ing. Gabriele Fatigati
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it Tel: +39 051 6171722
g.fatig...@cineca.it
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--
Ing. Gabriele Fatigati
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it Tel: +39 051 6171722
g.fatig...@cineca.it
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--
stephen.wor...@sophia.inria.fr
2004 route des lucioles - BP93
Sophia Antipolis
06902 CEDEX
Tel: 04 92 38 50 54
Fax: 04 97 15 53 51
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--
Ing. Gabriele Fatigati
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it Tel: +39 051 6171722
g.fatig...@cineca.it
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