NAME

       hwloc_distances_s

SYNOPSIS

       #include <hwloc.h>

   Data Fields
       unsigned relative_depth
       unsigned nbobjs
       float * latency
       float latency_max
       float latency_base

Detailed Description

       Distances between objects.

       One object may contain a distance structure describing distances between all its descendants at a given
       relative depth. If the containing object is the root object of the topology, then the distances are
       available for all objects in the machine.

       If the latency pointer is not NULL, the pointed array contains memory latencies (non-zero values), see
       below.

       In the future, some other types of distances may be considered. In these cases, latency may be NULL.

Field Documentation

   float* hwloc_distances_s::latency
       Matrix of latencies between objects, stored as a one-dimension array. May be NULL if the distances
       considered here are not latencies. Unless defined by the user, this currently contains latencies between
       NUMA nodes (as reported in the System Locality Distance Information Table (SLIT) in the ACPI
       specification), which may or may not be accurate. It corresponds to the latency for accessing the memory
       of one node from a core in another node.

       Values are normalized to get 1.0 as the minimal value in the matrix. Latency from i-th to j-th object is
       stored in slot i*nbobjs+j.

   float hwloc_distances_s::latency_base
       The multiplier that should be applied to latency matrix to retrieve the original OS-provided latencies.
       Usually 10 on Linux since ACPI SLIT uses 10 for local latency.

   float hwloc_distances_s::latency_max
       The maximal value in the latency matrix.

   unsigned hwloc_distances_s::nbobjs
       Number of objects considered in the matrix. It is the number of descendant objects at relative_depth
       below the containing object. It corresponds to the result of hwloc_get_nbobjs_inside_cpuset_by_depth().

   unsigned hwloc_distances_s::relative_depth
       Relative depth of the considered objects below the object containing this distance information.

Author

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