bionic (1) hwloc-distrib.1.gz

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 several processes to each package without
              specifying a single core for each of them.

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

       --reverse
              Distribute  by starting with the last objects first, and singlify CPU sets by keeping the last bit
              (instead of the first bit).

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

       --whole-system
              Do not consider administration limitations.

       --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 package, the topology should be restricted:

           $ hwloc-distrib --restrict $(hwloc-calc package: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)