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HWLOC-DISTRIB(1)			      hwloc				 HWLOC-DISTRIB(1)

NAME
       hwloc-distrib - Build a number of cpu masks distributed on the system

SYNOPSIS
       hwloc-distrib [options] <integer>

OPTIONS
       --single
	      Singlify each output to a single CPU.

       --taskset
	      Show  CPU  set strings in the format recognized by the taskset command-line program
	      instead of hwloc-specific CPU set string format.

       -v --verbose
	      Verbose messages.

       -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.

       --ignore <type>
	      Ignore all objects of type <type> in the topology.

       --from <type>
	      Distribute starting from objects of the given type instead of from the top  of  the
	      topology hierarchy, i.e. ignoring the structure given by objects above.

       --to <type>
	      Distribute  down	to objects of the given type instead of down to the bottom of the
	      topology hierarchy, i.e. ignoring the structure given by objects below.	This  may
	      be  useful  if  some latitude is desired for the binding, e.g. just bind on sockets
	      and not to precise cores or caches.

       --at <type>
	      Distribute among objects of the given type.  This is equivalent to specifying  both
	      --from and --to at the same time.

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

       --version
	      Report version and exit.

DESCRIPTION
       hwloc-distrib  generates  a series of CPU masks corresponding to a distribution of a given
       number of elements over the topology of the machine. The distribution is done  recursively
       from  the  top of the hierarchy (or from the level specified by option --from) down to the
       bottom of the hierarchy (or down to the level specified by option --to, or until only  one
       element remains), splitting the number of elements at each encountered hierarchy level not
       ignored by options --ignore.

       This can e.g. be used to distribute a set of processes  hierarchically  according  to  the
       topology of a machine. These masks can be used with hwloc-bind(1).

       NOTE:  It  is  highly  recommended that you read the hwloc(7) overview page before reading
       this man page.  Most of the concepts described in hwloc(7) directly apply  to  the  hwloc-
       bind utility.

EXAMPLES
       hwloc-distrib's operation is best described through several examples.

       If  4  processes  have to be distributed across a machine, their CPU masks may be obtained
       with:

	   $ hwloc-distrib 4
	   0x0000000f
	   0x00000f00
	   0x000000f0
	   0x0000f000

       To distribute only among the second socket, the topology should be restricted:

	   $ hwloc-distrib --restrict $(hwloc-calc socket:1) 4
	   0x00000010
	   0x00000020
	   0x00000040
	   0x00000080

       To get a single processor of each CPU masks (prevent migration in case of binding)

	   $ hwloc-distrib 4 --single
	   0x00000001
	   0x00000100
	   0x00000010
	   0x00001000

       Each output line may be converted independently with hwloc-calc:

	   $ hwloc-distrib 4 --single | hwloc-calc --taskset
	   0x1
	   0x100
	   0x10
	   0x1000

       To convert the output into a list of processors that may be passed to dplace -c	inside	a
       mpirun command line:

	   $ hwloc-distrib 4 --single | xargs hwloc-calc --pulist
	   0,8,4,16

RETURN VALUE
       Upon  successful  execution,  hwloc-distrib  displays  one  or more CPU mask strings.  The
       return value is 0.

       hwloc-distrib 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), hwloc-gather-topology(1)

1.7					   Apr 07, 2013 			 HWLOC-DISTRIB(1)
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