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Subject: Re: [hwloc-users] Process and thread binding
From: Gabriele Fatigati (g.fatigati_at_[hidden])
Date: 2011-09-12 08:17:20


Ok,

>A process is a container that contains one or several threads. The binding
is where >something can run. It's normal that "where a process can run" is
"where any of its >threads can run", which means it's the logical OR of
their binding.

Ok, now it's clear.

I'm using hwloc_get_last_cpu_location(), not get_cpubind(), sorry..

Well, the first thing to understand is what you're trying to do here. In the
vast majority of cases, binding a thread outside of the binding of the
corresponding process looks like buggy programming.

Mm, and why? In a hybrid code ( MPI + OpenMP), my idea is to bind a single
MPI process in one core, and his threads in other cores. Otherwise I have
all threads that runs on a single core..

2011/9/12 Brice Goglin <Brice.Goglin_at_[hidden]>

> **
> Le 12/09/2011 13:58, Gabriele Fatigati a écrit :
>
> Hi Brice,
>
> but in the manual is not written that get_cpubind() returns the logical
> OR of the binding of all threads... I ever understand that returns the
> bind of the calloer, where the caller can be process or thread..
>
>
> A process is a container that contains one or several threads. The binding
> is where something can run. It's normal that "where a process can run" is
> "where any of its threads can run", which means it's the logical OR of their
> binding.
>
>
>
>
> I'm mixing bind of process and threads, and I've noted that if the
> process and thread are on the same NUMA node, works well, also on different
> cores.
>
> If the NUMA node of process is different of NUMA node of threads, there
> is a problem.
>
>
> Well, the first thing to understand is what you're trying to do here. In
> the vast majority of cases, binding a thread outside of the binding of the
> corresponding process looks like buggy programming.
>
> Brice
>
>
> _______________________________________________
> hwloc-users mailing list
> hwloc-users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/hwloc-users
>

-- 
Ing. Gabriele Fatigati
HPC specialist
SuperComputing Applications and Innovation Department
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it                    Tel:   +39 051 6171722
g.fatigati [AT] cineca.it