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HWLOC-DISTANCES(1)		     hwloc		    HWLOC-DISTANCES(1)

NAME
       hwloc-distances - Displays distance matrices

SYNOPSIS
       hwloc-distances [options]

OPTIONS
       -l --logical
	      Display  hwloc  logical indexes (default)	instead	of physical/OS
	      indexes.

       -p --physical
	      Display OS/physical indexes instead of hwloc logical indexes.

       -i <file>, --input <file>
	      Read topology from XML file <file> (instead of  discovering  the
	      topology	on the local machine).	If <file> is "-", the standard
	      input is used.  XML support must have been compiled in to	 hwloc
	      for this option to be usable.

       -i <directory>, --input <directory>
	      Read  topology from the chroot specified by <directory> (instead
	      of discovering the topology on the local machine).  This	option
	      is  generally  only  available on	Linux.	The chroot was usually
	      created by gathering another machine topology with hwloc-gather-
	      topology.

       -i <specification>, --input <specification>
	      Simulate a fake hierarchy	(instead of discovering	 the  topology
	      on  the local machine). If <specification> is "node:2 pu:3", the
	      topology will contain two	NUMA nodes with	3 processing units  in
	      each of them.  The <specification> string	must end with a	number
	      of PUs.

       --if <format>, --input-format <format>
	      Enforce  the  input  in  the given format, among xml, fsroot and
	      synthetic.

       --restrict <cpuset>
	      Restrict the topology to the given cpuset.

       --whole-system
	      Do not consider administration limitations.

       -v --verbose
	      Verbose messages.

       --version
	      Report version and exit.

DESCRIPTION
       hwloc-distances displays	also distance matrices attached	to the	topol-
       ogy.   The  value  in the i-th row and j-th column is the distance from
       object #i to object #j.

       Unless defined by the user, matrices currently always contain  relative
       latencies  between  NUMA	nodes (which may or may	not be accurate).  See
       the definition of struct	hwloc_distances_s in  include/hwloc.h  or  the
       documentation for details.

       These latencies are normalized to the latency of	a local	(non-NUMA) ac-
       cess.   Hence 3.5 in row	#i column #j means that	the latency from cores
       in NUMA node #i to memory in NUMA node #j is 3.5	higher	than  the  la-
       tency  from  cores to their local memory.  A breadth-first traversal of
       the topology is performed starting from the root	to find	 all  distance
       matrices.

       NOTE:  lstopo may also display distance matrices	in its verbose textual
       output.	However	lstopo only prints  matrices  that  cover  the	entire
       topology	 while hwloc-distances also displays matrices that ignore part
       of the topology.

EXAMPLES
       On a quad-package opteron machine:

	   $ hwloc-distances
	   Latency matrix between 4 NUMANodes (depth 2)	by logical indexes:
	     index     0     1	   2	 3
		 0 1.000 1.600 2.200 2.200
		 1 1.600 1.000 2.200 2.200
		 2 2.200 2.200 1.000 1.600
		 3 2.200 2.200 1.600 1.000

RETURN VALUE
       Upon successful execution, hwloc-distances returns 0.

       hwloc-distances will return nonzero if any kind of error	 occurs,  such
       as (but not limited to) failure to parse	the command line.

SEE ALSO
       hwloc(7), lstopo(1)

1.11.13				 Jun 03, 2019		    HWLOC-DISTANCES(1)

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