hwloc-distrib - Online in the Cloud

PROGRAM:

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.

Use hwloc-distrib online using onworks.net services