The APIs that are described in this section enable the calling thread to navigate the lgroup hierarchy. The lgroup hierarchy is a directed acyclic graph that is similar to a tree, except that a node might have more than one parent. The root lgroup represents the whole machine and contains all of that machine's resources. The root lgroup is the lgroup with the highest latency value in the system. Each of the child lgroups contains a subset of the hardware that is in the root lgroup. Each child lgroup is bounded by a lower latency value. Locality groups that are closer to the root have more resources and a higher latency. Locality groups that are closer to the leaves have fewer resources and a lower latency. An lgroup can contain resources directly within its latency boundary. An lgroup can also contain leaf lgroups that contain their own sets of resources. The resources of leaf lgroups are available to the lgroup that encapsulates those leaf lgroups.