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Portable Hardware Locality (hwloc) Documentation: v0.9.2

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Interesting kind of part of the system, such as a Core, a Cache, a Memory node, etc. The different types detected by hwloc are detailed in the hwloc_obj_type_e enumeration.

They are topologically sorted by CPU set into a tree whose root is the System object which always exists.

CPU set

The set of logical processors logically included in an object, if any

Father object

The object logically containing the current object, for instance because its CPU set includes the CPU set of the current object.

Children objects

The object contained in the current object because their CPU set is included in the CPU set of the current object.


The number of children of an object

Sibling objects

Objects of the same type which have the same father

Sibling rank

Index to uniquely identify objecst of the same type which have the same father, numbered from 0 to the arity of the father minus one.

Cousin objects

Objects of the same type as the current object


Set of objects of the same type

OS index

The index that the OS uses to identify the object. This may sometimes be completely arbitrary or depend on the BIOS configuration.


Nesting level in the object tree, starting from the System object.

Logical index

Index to uniquely identify objects of the same type. This index is always linear from 0 to the number of objects of the level for that type, to express proximity. It could also be called cousin rank.

The following diagram can help to understand the vocabulary of the relationships by showing the example of a machine with two dual core non-SMT sockets, thus a topology with 4 levels.


It should be noted that for Processor objects, the logical index, computed linearly by hwloc, is not the same as the OS index.