HWLOC-DISTRIB(1) hwloc HWLOC-DISTRIB(1)
hwloc-distrib - Build a number of cpu masks distributed on the system
hwloc-distrib [options] <integer>
Singlify each output to a single CPU.
Show CPU set strings in the format recognized by the taskset command-line program
instead of hwloc-specific CPU set string format.
-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-
-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 all objects of type <type> in the topology.
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.
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.
Distribute among objects of the given type. This is equivalent to specifying both
--from and --to at the same time.
Restrict the topology to the given cpuset.
Report version and exit.
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-
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
$ hwloc-distrib 4
To distribute only among the second socket, the topology should be restricted:
$ hwloc-distrib --restrict $(hwloc-calc socket:1) 4
To get a single processor of each CPU masks (prevent migration in case of binding)
$ hwloc-distrib 4 --single
Each output line may be converted independently with hwloc-calc:
$ hwloc-distrib 4 --single | hwloc-calc --taskset
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
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.
1.7 Apr 07, 2013 HWLOC-DISTRIB(1)