Do not rely on the ordering or completeness of the values as new ones may be defined in the future! If you need to compare types, use hwloc_compare_types() instead.
Enumerator
HWLOC_OBJ_MACHINE
Machine. A set of processors and memory with cache coherency.
This type is always used for the root object of a topology, and never used anywhere else. Hence its parent is always NULL.
HWLOC_OBJ_PACKAGE
Physical package. The physical package that usually gets inserted into a socket on the motherboard. A processor package usually contains multiple cores, and possibly some dies.
HWLOC_OBJ_CORE
Core. A computation unit (may be shared by several PUs, aka logical processors).
HWLOC_OBJ_PU
Processing Unit, or (Logical) Processor. An execution unit (may share a core with some other logical processors, e.g. in the case of an SMT core).
This is the smallest object representing CPU resources, it cannot have any child except Misc objects.
Objects of this kind are always reported and can thus be used as fallback when others are not.
HWLOC_OBJ_L1CACHE
Level 1 Data (or Unified) Cache.
HWLOC_OBJ_L2CACHE
Level 2 Data (or Unified) Cache.
HWLOC_OBJ_L3CACHE
Level 3 Data (or Unified) Cache.
HWLOC_OBJ_L4CACHE
Level 4 Data (or Unified) Cache.
HWLOC_OBJ_L5CACHE
Level 5 Data (or Unified) Cache.
HWLOC_OBJ_L1ICACHE
Level 1 instruction Cache (filtered out by default).
HWLOC_OBJ_L2ICACHE
Level 2 instruction Cache (filtered out by default).
HWLOC_OBJ_L3ICACHE
Level 3 instruction Cache (filtered out by default).
HWLOC_OBJ_GROUP
Group objects. Objects which do not fit in the above but are detected by hwloc and are useful to take into account for affinity. For instance, some operating systems expose their arbitrary processors aggregation this way. And hwloc may insert such objects to group NUMA nodes according to their distances. See also What are these Group objects in my topology?.
NUMA node. An object that contains memory that is directly and byte-accessible to the host processors. It is usually close to some cores (the corresponding objects are descendants of the NUMA node object in the hwloc tree).
This is the smallest object representing Memory resources, it cannot have any child except Misc objects. However it may have Memory-side cache parents.
NUMA nodes may correspond to different kinds of memory (DRAM, HBM, CXL-DRAM, etc.). When hwloc is able to guess that kind, it is specified in the subtype field of the object. See also Normal attributes in the main documentation.
There is always at least one such object in the topology even if the machine is not NUMA.
Memory objects are not listed in the main children list, but rather in the dedicated Memory children list.
NUMA nodes have a special depth HWLOC_TYPE_DEPTH_NUMANODE instead of a normal depth just like other objects in the main tree.
HWLOC_OBJ_BRIDGE
Bridge (filtered out by default). Any bridge (or PCI switch) that connects the host or an I/O bus, to another I/O bus.
I/O objects are not listed in the main children list, but rather in the dedicated io children list. I/O objects have NULL CPU and node sets.
HWLOC_OBJ_MISC
Miscellaneous objects (filtered out by default). Objects without particular meaning, that can e.g. be added by the application for its own use, or by hwloc for miscellaneous objects such as MemoryModule (DIMMs).
These objects are not listed in the main children list, but rather in the dedicated misc children list. Misc objects may only have Misc objects as children, and those are in the dedicated misc children list as well. Misc objects have NULL CPU and node sets.
HWLOC_OBJ_MEMCACHE
Memory-side cache (filtered out by default). A cache in front of a specific NUMA node.
This object always has at least one NUMA node as a memory child.
Memory objects are not listed in the main children list, but rather in the dedicated Memory children list.
Memory-side cache have a special depth HWLOC_TYPE_DEPTH_MEMCACHE instead of a normal depth just like other objects in the main tree.
HWLOC_OBJ_DIE
Die within a physical package. A subpart of the physical package, that contains multiple cores.
Some operating systems (e.g. Linux) may expose a single die per package even if the hardware does not support dies at all. To avoid showing such non-existing dies, the corresponding hwloc backend may filter them out. This is functionally equivalent to HWLOC_TYPE_FILTER_KEEP_STRUCTURE being enforced.
Types shouldn't be compared as they are, since newer ones may be added in the future.
Returns
A negative integer if type1 objects usually include type2 objects.
A positive integer if type1 objects are usually included in type2 objects.
0 if type1 and type2 objects are the same.
HWLOC_TYPE_UNORDERED if objects cannot be compared (because neither is usually contained in the other).
Note
Object types containing CPUs can always be compared (usually, a machine contains packages, which contain caches, which contain cores, which contain PUs).
This does not mean that the actual topology will respect that order: e.g. as of today cores may also contain caches, and packages may also contain nodes. This is thus just to be seen as a fallback comparison method.