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Portable Hardware Locality (hwloc) Documentation: v1.3.3

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Interoperability With Other Software

Although hwloc offers its own portable interface, it still may have to interoperate with specific or non-portable libraries that manipulate similar kinds of objects. hwloc therefore offers several specific "helpers" to assist converting between those specific interfaces and hwloc.

Some external libraries may be specific to a particular OS; others may not always be available. The hwloc core therefore generally does not explicitly depend on these types of libraries. However, when a custom application uses or otherwise depends on such a library, it may optionally include the corresponding hwloc helper to extend the hwloc interface with dedicated helpers.

Linux specific features

hwloc/linux.h offers Linux-specific helpers that utilize some non-portable features of the Linux system, such as binding threads through their thread ID ("tid") or parsing kernel CPU mask files.

Linux libnuma

hwloc/linux-libnuma.h provides conversion helpers between hwloc CPU sets and libnuma-specific types, such as nodemasks and bitmasks. It helps you use libnuma memory-binding functions with hwloc CPU sets.


hwloc/glibc-sched.h offers conversion routines between Glibc and hwloc CPU sets in order to use hwloc with functions such as sched_setaffinity().

OpenFabrics Verbs

hwloc/openfabrics-verbs.h helps interoperability with the OpenFabrics Verbs interface. For example, it can return a list of processors near an OpenFabrics device. Note that if I/O device discovery is enabled, such devices may also appear as PCI objects and as OS objects in the topology.

Myrinet Express

hwloc/myriexpress.h offers interoperability with the Myrinet Express interface. It can return the list of processors near a Myrinet board managed by the MX driver. Note that if I/O device discovery is enabled, such boards may also appear as PCI objects in the topology.


hwloc/cuda.h and hwloc/cudart.h enable interoperability with NVIDIA CUDA Driver and Runtime interfaces. For instance, it may return the list of processors near NVIDIA GPUs. Note that if I/O device discovery is enabled, GPUs may also appear as PCI objects in the topology.

Taskset command-line tool

The taskset command-line tool is widely used for binding processes. It manipulates CPU set strings in a format that is slightly different from hwloc's one (it does not divide the string in fixed-size subsets and separates them with commas). To ease interoperability, hwloc offers routines to convert hwloc CPU sets from/to taskset-specific string format. Most hwloc command-line tools also support the –taskset option to manipulate taskset-specific strings.