HWLOC-CALC(1) hwloc HWLOC-CALC(1)
hwloc-calc - Operate on cpu mask strings and objects
hwloc-calc [options] <location1> [<location2> [...] ]
Note that hwloc(7) provides a detailed explanation of the hwloc system and of valid <loca-
tion> formats; it should be read before reading this man page.
Use OS/physical indexes instead of logical indexes for both input and output.
Use logical indexes instead of physical/OS indexes for both input and output
Use OS/physical indexes instead of logical indexes for input.
Use logical indexes instead of physical/OS indexes for input (default).
Use OS/physical indexes instead of logical indexes for output.
Use logical indexes instead of physical/OS indexes for output (default, except
for cpusets which are always physical).
-N --number-of <type|depth>
Report the number of objects of the given type or depth that intersect the CPU
set. This is convenient for finding how many cores, NUMA nodes or PUs are
available in a machine.
-I --intersect <type|depth>
Find the list of objects of the given type or depth that intersect the CPU set
and report the comma-separated list of their indexes instead of the cpu mask
string. This may be used for determining the list of objects above or below the
input objects. When combined with --physical, the list is convenient to pass to
external tools such as taskset or numactl --physcpubind or --membind. This is
different from --largest since the latter requires that all reported objects are
strictly included inside the input objects.
-H --hierarchical <type1>.<type2>...
Find the list of objects of type <type2> that intersect the CPU set and report
the space-separated list of their hierarchical indexes with respect to <type1>,
<type2>, etc. For instance, if socket.core is given, the output would be
Socket:1.Core:2 Socket:2.Core:3 if the input contains the third core of the sec-
ond socket and the fourth core of the third socket.
--largest Report (in a human readable format) the list of largest objects which exactly
include all input objects. None of these output objects intersect each other,
and the sum of them is exactly equivalent to the input. No largest object is
included in the input This is different from --intersect where reported objects
may not be strictly included in the input.
Change the field separator in the output. By default, a space is used to sepa-
rate output objects (for instance when --hierarchical or --largest is given)
while a comma is used to separate indexes (for instance when --intersect is
--single Singlify the output to a single CPU.
--taskset Display CPU set strings in the format recognized by the taskset command-line
program instead of hwloc-specific CPU set string format. This option has no
impact on the format of input CPU set strings, both formats are always accepted.
Restrict the topology to the given cpuset.
-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
-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.
Hide non-fatal error messages. It mostly includes locations pointing to non-
--version Report version and exit.
hwloc-calc generates and manipulates CPU mask strings or objects. Both input and output
may be either objects (with physical or logical indexes), CPU lists (with physical or log-
ical indexes), or CPU mask strings (always physically indexed).
If objects or CPU mask strings are given on the command-line, they are combined and a sin-
gle output is printed. If no object or CPU mask strings are given on the command-line,
the program will read the standard input. It will combine multiple objects or CPU mask
strings that are given on the same line of the standard input line with spaces as separa-
tors. Different input lines will be processed separately.
Command-line arguments and options are processed in order. For instance, it means that
changing the type of input indexes with --li or changing the input topology with -i only
affects the processing the following arguments.
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-calc's operation is best described through several examples.
To display the (physical) CPU mask corresponding to the second socket:
$ hwloc-calc socket:1
To display the (physical) CPU mask corresponding to the third socket, excluding its even
numbered logical processors:
$ hwloc-calc socket:2 ~PU:even
To combine two (physical) CPU masks:
$ hwloc-calc 0x0000ffff 0xff000000
To display the list of logical numbers of processors included in the second socket:
$ hwloc-calc --intersect PU socket:1
To bind GNU OpenMP threads logically over the whole machine, we need to use physical num-
ber output instead:
$ export GOMP_CPU_AFFINITY=`hwloc-calc --physical-output --intersect PU machine:0`
$ echo $GOMP_CPU_AFFINITY
To display the list of NUMA nodes, by physical indexes, that intersect a given (physical)
$ hwloc-calc --physical --intersect NUMAnode 0xf0f0f0f0
To display the physical index of a processor given by its logical index:
$ hwloc-calc PU:2 --physical-output --intersect PU
To display the set of CPUs near network interface eth0:
$ hwloc-calc os=eth0
To display the indexes of sockets near PCI device whose bus ID is 0000:01:02.0:
$ hwloc-calc pci=0000:01:02.0 --intersect Socket
To display the list of per-socket cores that intersect the input:
$ hwloc-calc 0x00003c00 --hierarchical socket.core
To display the (physical) CPU mask of the entire topology except the third socket:
$ hwloc-calc all ~socket:3
To combine both physical and logical indexes as input:
$ hwloc-calc PU:2 --physical-input PU:3
To synthetize a set of cores into largest objects on a 2-node 2-socket 2-core machine:
$ hwloc-calc core:0 --largest
$ hwloc-calc core:0-1 --largest
$ hwloc-calc core:4-7 --largest
$ hwloc-calc core:2-6 --largest
Socket:1 Socket:2 Core:6
$ hwloc-calc socket:2 --largest
$ hwloc-calc socket:2-3 --largest
To get the set of first threads of all cores:
$ hwloc-calc core:all.pu:0
This can also be very useful in order to make GNU OpenMP use exactly one thread per core,
and in logical core order:
$ export OMP_NUM_THREADS=`hwloc-calc --number-of core machine:0`
$ echo $OMP_NUM_THREADS
$ export GOMP_CPU_AFFINITY=`hwloc-calc --physical-output --intersect PU core:all.pu:0`
$ echo $GOMP_CPU_AFFINITY
Upon successful execution, hwloc-calc displays the (physical) CPU mask string, (physical
or logical) object list, or (physical or logical) object number list. The return value is
hwloc-calc will return nonzero if any kind of error occurs, such as (but not limited to):
failure to parse the command line.
hwloc(7), lstopo(1), hwloc-info(1), hwloc-gather-topology(1)
1.7 Apr 07, 2013 HWLOC-CALC(1)