|Network Locality (netloc)|
New hwloc companion
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|hwloc v1.8 released|
New feature release
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|hwloc v1.7.2 released|
New stable release
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|hwloc tutorial material|
Slides and code available
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The Portable Hardware Locality (hwloc) software package provides a
portable abstraction (across OS, versions, architectures, ...) of the
hierarchical topology of modern architectures, including NUMA memory
nodes, sockets, shared caches, cores and simultaneous
multithreading. It also gathers various system attributes such as
cache and memory information as well as the locality of I/O devices
such as network interfaces, InfiniBand HCAs or GPUs.
It primarily aims at helping
applications with gathering information about modern computing
hardware so as to exploit it accordingly and efficiently.
Portability and support
hwloc supports the following operating systems:
- Linux (including old kernels not having sysfs topology
information, with knowledge of cpusets, offline CPUs, ScaleMP vSMP,
NumaScale NumaConnect, and Kerrighed support)
- Darwin / OS X
- FreeBSD and its variants (such as kFreeBSD/GNU)
- OSF/1 (a.k.a., Tru64)
- Microsoft Windows
- IBM BlueGene/Q Compute Node Kernel (CNK)
Since it uses standard Operating System information, hwloc's support is
almost always independent from the processor type (x86, powerpc, ia64, ...),
and just relies on the Operating System support. The only exception to this is
kFreeBSD, which does not support topology information, and hwloc thus uses an
x86-only CPUID-based backend (which could be used for other OSes too).
To check whether hwloc works on a particular machine, just try to build
it and run lstopo If some things do not look right (e.g. bogus or
missing cache information), see Questions and bugs below
hwloc may display the topology in multiple convenient formats (see
It also offers a powerful programming interface to gather information
about the hardware, bind processes, and much more.
More details are available in the Documentation
(in both PDF and HTML). The documentation for each version contains
outputs and an API interface example (these links are for v1.8).
The materials from several hwloc tutorials is
Getting and using hwloc
The latest hwloc releases are available on the
The GIT repository is also accessible for
Perl bindings are available from Bernd Kallies
Python bindings are available from Guy Streeter
as Fedora RPM and tarball
or within their git tree
The following software already benefit from hwloc or are being
ported to it:
- MPI implementations and tools
- Runtime systems and compilers
- The ForestGOMP
OpenMP platform for hierarchical architectures
- The StarPU
runtime system for heterogeneous multicore architectures
- The Directed Acyclic Graph Unified Environment
- The Qthreads project (site 1, site 2)
- The Rose compiler
- Parallel scientific libraries
- Resource manager and job schedulers
- and even more!
How do you pronounce "hwloc"?
When in doubt, say "hardware locality."
Some of the core developers say "H. W. Loke"; others say
"H. W. Lock". We've heard several other pronunciations as well. We
don't really have a strong preference for how you say it; we
chose the name for its Google-ability, not its pronunciation.
But now at least you know how we pronounce it. :-)
Questions and bugs
Questions, comments, and bugs should be sent to hwloc mailing lists. When
appropriate, please attach the /proc + /sys tarball
generated by the installed script hwloc-gather-topology.sh in
version v1.1 and later when submitting problems about Linux (or
tests/linux/gather-topology.sh in v1.0.x), or send the
output of kstat cpu_info in the Solaris case, or the output
of sysctl hw in the Darwin or BSD cases. Also make sure you
run a recent OS (e.g. Linux kernel) and possibly a recent BIOS too
since hwloc gathers topology information from them. Passing
--enable-debug to ./configure also enables a lot of
helpful debugging information.
Also be sure to see the hwloc wiki and bug tracking
Many hwloc-related publications are listed at the bottom of the
Inria hwloc research page
and in the
Open MPI publication list.
If you are looking for general-purpose hwloc citations, please use this one:
François Broquedis, Jérôme Clet-Ortega, Stéphanie Moreaud, Nathalie Furmento, Brice Goglin, Guillaume Mercier, Samuel Thibault, and Raymond Namyst.
hwloc: a Generic Framework for Managing Hardware Affinities in HPC Applications.
In Proceedings of the 18th Euromicro International Conference on Parallel, Distributed and Network-Based Processing (PDP2010),
Pisa, Italia, February 2010.
IEEE Computer Society Press.
This paper (available here)
introduces hwloc, its goals and its implementation.
It then shows how hwloc may be used by MPI implementations and OpenMP
runtime systems as a way to carefully place processes and adapt communication
strategies to the underlying hardware.
History / credits
hwloc is the evolution and merger of the libtopology
project and the Portable Linux Processor Affinity
(PLPA) project. Because of functional and ideological overlap,
these two code bases and ideas were merged and released under the name
"hwloc" as an Open MPI sub-project.
libtopology was initially developed by the Inria Runtime Team-Project
(headed by Raymond
Namyst). PLPA was initially developed by the Open MPI development
team as a sub-project. Both are now deprecated in favor of hwloc,
which is distributed here as an Open MPI sub-project.
Portability tests are performed thanks to
the Inria Continuous Integration platform,
and the Inria PIPOL platform.