[bogus section]

This section is not used by PRTE code.  But we have to put a RST
section title in this file somewhere, or Sphinx gets unhappy.  So we
put it in a section that is ignored by PRTE code.


Hello, world
============

[version]

%s (%s) %s

%s

[usage]

%s (%s) %s

Usage: %s [OPTION]...

Initiate an instance of the PMIx Reference RTE (PRRTE) DVM

The following list of command line options are available. Note that
more detailed help for any option can be obtained by adding that
option to the help request as "--help <option>".

+----------------------+-----------------------------------------------+
|                      | General Options                               |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "-h" | "--help"      | This help message                             |
+----------------------+-----------------------------------------------+
| "-h" | "--help       | Help for the specified option                 |
| <arg0>"              |                                               |
+----------------------+-----------------------------------------------+
| "-v" | "--verbose"   | Enable typical debug options                  |
+----------------------+-----------------------------------------------+
| "-V" | "--version"   | Print version and exit                        |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Debug Options                                 |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--debug-daemons"    | Debug daemons — if not set, any "verbose"     |
|                      | settings will be limited to the prterun       |
|                      | itself to reduce clutter                      |
+----------------------+-----------------------------------------------+
| "--debug-daemons-    | Enable debugging of any PRRTE daemons used by |
| file"                | this application, storing their verbose       |
|                      | output in files                               |
+----------------------+-----------------------------------------------+
| "--display <arg0>"   | Options for displaying information about the  |
|                      | allocation and job.                           |
+----------------------+-----------------------------------------------+
| "--spawn-timeout     | Timeout the job if spawn takes more than the  |
| <seconds>"           | specified number of seconds                   |
+----------------------+-----------------------------------------------+
| "--timeout           | Timeout the job if execution is not complete  |
| <seconds>"           | after the specified number of seconds         |
+----------------------+-----------------------------------------------+
| "--get-stack-traces" | Get stack traces of all application procs on  |
|                      | timeout                                       |
+----------------------+-----------------------------------------------+
| "--leave-session-    | Do not discard stdout/stderr of remote PRRTE  |
| attached"            | daemons                                       |
+----------------------+-----------------------------------------------+
| "--report-state-on-  | Report all job and process states upon        |
| timeout"             | timeout                                       |
+----------------------+-----------------------------------------------+
| "--stop-on-exec"     | If supported, stop each specified process at  |
|                      | start of execution                            |
+----------------------+-----------------------------------------------+
| "--stop-in-init"     | Direct the specified processes to stop in     |
|                      | "PMIx_Init"                                   |
+----------------------+-----------------------------------------------+
| "--stop-in-app"      | Direct the specified processes to stop at an  |
|                      | application-controlled location               |
+----------------------+-----------------------------------------------+
| "--do-not-launch"    | Perform all necessary operations to prepare   |
|                      | to launch the application, but do not         |
|                      | actually launch it (usually used to test      |
|                      | mapping patterns)                             |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Output Options                                |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--output <arg0>"    | Comma-delimited list of options that control  |
|                      | how output is generated.                      |
+----------------------+-----------------------------------------------+
| "--report-child-     | Return the exit status of the primary job     |
| jobs-separately"     | only                                          |
+----------------------+-----------------------------------------------+
| "--xterm <ranks>"    | Create a new xterm window for each of the     |
|                      | comma-delimited ranges of application process |
|                      | ranks                                         |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Input Options                                 |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--stdin <ranks>"    | Specify application rank(s) to receive stdin  |
|                      | [integer ranks, "rank", "all", "none"]        |
|                      | (default: "0", indicating rank 0)             |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Placement Options                             |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--map-by <type>"    | Mapping Policy for job                        |
+----------------------+-----------------------------------------------+
| "--rank-by <type>"   | Ranking Policy for job                        |
+----------------------+-----------------------------------------------+
| "--bind-to <type>"   | Binding policy for job.                       |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Launch Options                                |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--runtime-options   | Comma-delimited list of runtime directives    |
| <arg0>"              | for the job (e.g., do not abort if a process  |
|                      | exits on non-zero status)                     |
+----------------------+-----------------------------------------------+
| "-c" | "--np <num>"  | Number of processes to run                    |
+----------------------+-----------------------------------------------+
| "-n" | "--n <num>"   | Number of processes to run                    |
+----------------------+-----------------------------------------------+
| "-N" | "--npernode   | Run designated number of processes on each    |
| <num>"               | node                                          |
+----------------------+-----------------------------------------------+
| "--personality       | Specify the personality to be used            |
| <name>"              |                                               |
+----------------------+-----------------------------------------------+
| "-H" | "--host       | List of hosts to invoke processes on          |
| <hosts>"             |                                               |
+----------------------+-----------------------------------------------+
| "--hostfile <file>"  | Provide a hostfile                            |
+----------------------+-----------------------------------------------+
| "--machinefile       | Provide a hostfile (synonym for "--hostfile") |
| <file>"              |                                               |
+----------------------+-----------------------------------------------+
| "--pmixmca <key>     | Pass context-specific PMIx MCA parameters;    |
| <value>"             | they are considered global if only one        |
|                      | context is specified ("key" is the parameter  |
|                      | name; "value" is the parameter value)         |
+----------------------+-----------------------------------------------+
| "--gpmixmca <key>    | Pass global PMIx MCA parameters that are      |
| <value>"             | applicable to all contexts ("key" is the      |
|                      | parameter name; "value" is the parameter      |
|                      | value)                                        |
+----------------------+-----------------------------------------------+
| "--preload-files     | Preload the comma separated list of files to  |
| <files>"             | the remote machines current working directory |
|                      | before starting the remote process.           |
+----------------------+-----------------------------------------------+
| "--prtemca <key>     | Pass context-specific PRRTE MCA parameters to |
| <value>"             | the DVM                                       |
+----------------------+-----------------------------------------------+
| "--pset <name>"      | User-specified name assigned to the processes |
|                      | in their given application                    |
+----------------------+-----------------------------------------------+
| "-s" | "--preload-   | Preload the binary on the remote machine      |
| binary"              | before starting the remote process.           |
+----------------------+-----------------------------------------------+
| "--set-cwd-to-       | Set the working directory of the started      |
| session-dir"         | processes to their session directory          |
+----------------------+-----------------------------------------------+
| "--show-progress"    | Output a brief periodic report on launch      |
|                      | progress                                      |
+----------------------+-----------------------------------------------+
| "--wd <dir>"         | Synonym for "--wdir"                          |
+----------------------+-----------------------------------------------+
| "--wdir <dir>"       | Set the working directory of the started      |
|                      | processes                                     |
+----------------------+-----------------------------------------------+
| "-x <name>"          | Export an environment variable, optionally    |
|                      | specifying a value                            |
+----------------------+-----------------------------------------------+

+----------------------+-----------------------------------------------+
|                      | Specific Options                              |
+----------------------+-----------------------------------------------+
| Option               | Description                                   |
|======================|===============================================|
| "--allow-run-as-     | Allow execution as root (**STRONGLY           |
| root"                | DISCOURAGED**)                                |
+----------------------+-----------------------------------------------+
| "--forward-signals   | Comma-delimited list of additional signals    |
| <signals>"           | (names or integers) to forward to application |
|                      | processes ["none" => forward nothing].        |
+----------------------+-----------------------------------------------+
| "--keepalive <arg0>" | Pipe to monitor — DVM will terminate upon     |
|                      | closure                                       |
+----------------------+-----------------------------------------------+
| "--launch-agent      | Name of daemon executable used to start       |
| <exe>"               | processes on remote nodes (default: "prted")  |
+----------------------+-----------------------------------------------+
| "--max-vm-size       | Number of daemons to start                    |
| <num>"               |                                               |
+----------------------+-----------------------------------------------+
| "--no-ready-msg"     | Do not print a DVM ready message              |
+----------------------+-----------------------------------------------+
| "--noprefix"         | Disable automatic "--prefix" behavior         |
+----------------------+-----------------------------------------------+
| "--prefix <dir>"     | Prefix to be used to look for RTE executables |
+----------------------+-----------------------------------------------+
| "--report-pid        | Print out PID on stdout ("-"), stderr ("+"),  |
| <arg0>"              | or a file [anything else]                     |
+----------------------+-----------------------------------------------+
| "--report-uri        | Print out URI on stdout ("-"), stderr ("+"),  |
| <arg0>"              | or a file [anything else]                     |
+----------------------+-----------------------------------------------+
| "--set-sid"          | Direct the DVM daemons to separate from the   |
|                      | current session                               |
+----------------------+-----------------------------------------------+
| "--singleton <id>"   | ID of the singleton process that started us   |
+----------------------+-----------------------------------------------+
| "--tmpdir <dir>"     | Set the root for the session directory tree   |
+----------------------+-----------------------------------------------+
| "--tune <files>"     | File(s) containing MCA params for tuning DVM  |
|                      | operations                                    |
+----------------------+-----------------------------------------------+
| "--dvm <arg>"        | Use a persistent DVM instead of instantiating |
|                      | independent runtime infrastructure. The       |
|                      | argument indicates the PID, URI, file         |
|                      | containing the URI, or namespace of the DVM.  |
+----------------------+-----------------------------------------------+

Report bugs to %s

[dvm]

Utilize an existing persistent DVM instead of instantiating an
independent runtime infrastructure. This mimics the "prun" command,
but is provided as a convenience option for those wanting to embed the
"prterun" command in a script that can be optionally used to run
either independently or under a persistent DVM.

A required argument is passed to the "--dvm" directive to specify the
location of the DVM controller (e.g., "--dvm pid:12345") or by passing
the string "search" to instead search for an existing controller.

Supported options include:

* "search": directs the tool to search for available DVM controllers
  it is authorized to use, connecting to the first such candidate it
  finds.

* "pid:<arg>": provides the PID of the target DVM controller. This can
  be given as either the PID itself (arg = int) or the path to a file
  that contains the PID (arg = "file:<path>")

* "file:<path>": provides the path to a PMIx rendezvous file that is
  output by PMIx servers — the file contains all the required
  information for completing the connection

* "uri:<arg>": specifies the URI of the DVM controller, or the name of
  the file (specified as "file:filename") that contains that info

* "ns:<arg>": specifies the namespace of the DVM controller

* "system": exclusively find and use the system-level DVM controller

* "system-first": look for a system-level DVM controller, fall back to
  searching for an available DVM controller the command is authorized
  to use if a system-level controller is not found

Examples:

   prterun --dvm file:dvm_uri.txt --np 4 ./a.out

   prterun --dvm pid:12345 --np 4 ./a.out

   prterun --dvm uri:file:dvm_uri.txt --np 4 ./a.out

   prterun --dvm ns:prte-node1-2095 --np 4 ./a.out

   prterun --dvm pid:file:prte_pid.txt --np 4 ./a.out

   prterun --dvm search --np 4 ./a.out

[prtemca]

Pass a PRRTE MCA parameter.

Syntax: "--prtemca <key> <value>", where "key" is the parameter name
and "value" is the parameter value.

[pmixmca]

Pass a PMIx MCA parameter

Syntax: "--pmixmca <key> <value>", where "key" is the parameter name
and "value" is the parameter value.

[gpmixmca]

Syntax: "--gpmixmca <key> <value>"

where "key" is the parameter name and "value" is the parameter value.
The "g" prefix indicates that this PMIx parameter is to be applied to
_all_ application contexts and not just the one in which the directive
appears.

[tune]

Comma-delimited list of one or more files containing PRRTE and PMIx
MCA params for tuning DVM and/or application operations. Parameters in
the file will be treated as *generic* parameters and subject to the
translation rules/uncertainties.  See "--help mca" for more
information.

Syntax in the file is:

   param = value

with one parameter and its associated value per line. Empty lines and
lines beginning with the "#" character are ignored.

[stream]

Adjust buffering for stdout/stderr.  Allowable values:

* 0: unbuffered

* 1: line buffered

* 2: fully buffered

[system-server]

Start prterun and its daemons as the system server on their nodes

[set-sid]

Direct the DVM (controller and daemons) to separate from the current
session

[report-pid]

Printout prterun's PID on stdout ("-"), stderr ("+"), or a file
(anything else).

[report-uri]

Printout prterun's URI on stdout ("-"), stderr ("+"), or a file
(anything else).

[test-suicide]

Test DVM cleanup upon daemon failure by having one daemon suicide
after delay

[singleton]

"prterun" is being started by a singleton process (i.e., one not
started by prterun) — the argument must be the PMIx ID of the
singleton process that started us

[keepalive]

Pipe for prterun to monitor — job will terminate upon closure

[launch-agent]

Name of daemon executable used to start processes on remote nodes
(default: "prted").

This is the executable prterun shall start on each remote node when
establishing the DVM.

[max-vm-size]

Maximum number of daemons to start

[debug-daemons]

Debug daemon output enabled. This is a somewhat limited stream of
information normally used to simply confirm that the daemons started.
Includes leaving the output streams open.

[debug-daemons-file]

Debug daemon output is enabled and all output from the daemons is
redirected into files with names of the form:

   output-prted-<daemon-nspace>-<nodename>.log

These names avoid conflict on shared file systems. The files are
located in the top-level session directory assigned to the DVM.

See the "Session directory" HTML documentation for additional details
about the PRRTE session directory.

[leave-session-attached]

Do not discard stdout/stderr of remote PRRTE daemons. The primary use
for this option is to ensure that the daemon output streams (i.e.,
stdout and stderr) remain open after launch, thus allowing the user to
see any daemon-generated error messages. Otherwise, the daemon will
"daemonize" itself upon launch, thereby closing its output streams.

[tmpdir]

Define the root location for the PRRTE session directory tree

See the "Session directory" HTML documentation for additional details
about the PRRTE session directory.

[prefix]

Prefix to be used to look for PRRTE executables. PRRTE automatically
sets the prefix for remote daemons if it was either configured with
the "--enable-prte-prefix-by-default" option OR prte itself was
executed with an absolute path to the prte command. This option
overrides those settings, if present, and forces use of the provided
path.

[noprefix]

Disable automatic "--prefix" behavior. PRRTE automatically sets the
prefix for remote daemons if it was either configured with the "--
enable-prte-prefix-by-default" option OR prte itself was executed with
an absolute path to the "prte" command. This option disables that
behavior.

[forward-signals]

Comma-delimited list of additional signals (names or integers) to
forward to application processes ("none" = forward nothing). Signals
provided by default include SIGTSTP, SIGUSR1, SIGUSR2, SIGABRT,
SIGALRM, and SIGCONT.

[allow-run-as-root]

Allow execution as root **(STRONGLY DISCOURAGED)**.

Running as root exposes the user to potentially catastrophic file
system corruption and damage — e.g., if the user accidentally points
the root of the session directory to a system required point, this
directory and all underlying elements will be deleted upon job
completion, thereby rendering the system inoperable.

It is recognized that some environments (e.g., containers) may require
operation as root, and that the user accepts the risks in those
scenarios. Accordingly, one can override PRRTE's run-as-root
protection by providing one of the following:

* The "--allow-run-as-root" command line directive

* Adding **BOTH** of the following environmental parameters:

     * "PRTE_ALLOW_RUN_AS_ROOT=1"

     * "PRTE_ALLOW_RUN_AS_ROOT_CONFIRM=1"

Again, we recommend this only be done if absolutely necessary.

[report-child-jobs-separately]

Return the exit status of the primary job only

[timeout]

Timeout the job if execution time exceeds the specified number of
seconds

[report-state-on-timeout]

Report all job and process states upon timeout

[get-stack-traces]

Get stack traces of all application procs on timeout

[spawn-timeout]

Timeout the job if spawn takes more than the specified number of
seconds

[np]

Specify number of application processes to be started

[n] Specify number of application processes to be started

[N]

Specify number of application processes per node to be started

[app]

Provide an appfile; ignore all other command line options

[xterm]

Create a new xterm window and display output from the specified ranks
there.  Ranks are specified as a comma-delimited list of ranges —
e.g., "1,3-6,9", or as "all".

[stop-on-exec]

If supported, stop each process at start of execution

[stop-in-init]

Include the "PMIX_DEBUG_STOP_IN_INIT" attribute in the application's
job info directing that the specified ranks stop in PMIx_Init pending
release. Ranks are specified as a comma-delimited list of ranges —
e.g., "1,3-6,9", or as "all".

[stop-in-app]

Include the "PMIX_DEBUG_STOP_IN_APP" attribute in the application's
job info directing that the specified ranks stop at an application-
determined point pending release. Ranks are specified as a comma-
delimited list of ranges — e.g., "1,3-6,9", or as "all".

[x]

Export an environment variable, optionally specifying a value. For
example:

* "-x foo" exports the environment variable "foo" and takes its value
  from the current environment.

* "-x foo=bar" exports the environment variable name "foo" and sets
  its value to "bar" in the started processes.

* "-x foo*" exports all current environmental variables starting with
  "foo".

[wdir]

Set the working directory of the started processes

[wd]

Synonym for --wdir

[set-cwd-to-session-dir]

Set the working directory of the started processes to their session
directory

[path]

Path to be used to look for executables to start processes

[show-progress]

Output a brief periodic report on launch progress

[pset]

User-specified name assigned to the processes in their given
application

[hostfile]

PRRTE supports several levels of user-specified hostfiles based on an
established precedence order. Users can specify a hostfile that
contains a list of nodes to be used for the job, or can provide a
comma-delimited list of nodes to be used for that job via the "--host"
command line option.

The precedence order applied to these various options depends to some
extent on the local environment. The following table illustrates how
host and hostfile directives work together to define the set of hosts
upon which a DVM will execute the job in the absence of a resource
manager (RM):

+---------+------------+-----------------------------------------------+
| host    | hostfile   | Result                                        |
|=========|============|===============================================|
| unset   | unset      | The DVM will utilize all its available        |
|         |            | resources when mapping the job.               |
+---------+------------+-----------------------------------------------+
| set     | unset      | Host option defines resource list for the job |
+---------+------------+-----------------------------------------------+
| unset   | set        | Hostfile defines resource list for the job    |
+---------+------------+-----------------------------------------------+
| set     | set        | Hostfile defines resource list for the job,   |
|         |            | then host filters the list to define the      |
|         |            | final set of nodes to be used for the job     |
+---------+------------+-----------------------------------------------+

Hostfiles (sometimes called "machine files") are a combination of two
things:

1. A listing of hosts on which to launch processes.

2. Optionally, limit the number of processes which can be launched on
   each host.

Hostfile syntax consists of one node name on each line, optionally
including a designated number of "slots":

   # This is a comment line, and will be ignored
   node01  slots=10
   node13  slots=5

   node15
   node16
   node17  slots=3
   ...

Blank lines and lines beginning with a "#" are ignored.

A "slot" is the PRRTE term for an allocatable unit where we can launch
a process.  See the section on definition of the term "slot" for a
longer description of slots.

In the absence of the "slot" parameter, PRRTE will assign either the
number of slots to be the number of CPUs detected on the node or the
resource manager-assigned value if operating in the presence of an RM.

Important:

  If using a resource manager, the user-specified number of slots is
  capped by the RM-assigned value.


Relative host indexing
----------------------

Hostfile and "--host" specifications can also be made using relative
indexing. This allows a user to stipulate which hosts are to be used
for a given app context without specifying the particular host name,
but rather its relative position in the allocation.

This can probably best be understood through consideration of a few
examples. Consider the case where a DVM is comprised of a set of nodes
named "foo1", "foo2", "foo3", "foo4". The user wants the first app
context to have exclusive use of the first two nodes, and a second app
context to use the last two nodes. Of course, the user could printout
the allocation to find the names of the nodes allocated to them and
then use "--host" to specify this layout, but this is cumbersome and
would require hand-manipulation for every invocation.

A simpler method is to utilize PRRTE's relative indexing capability to
specify the desired layout. In this case, a command line containing:

   --host +n1,+n2 ./app1 : --host +n3,+n4 ./app2

would provide the desired pattern. The "+" syntax indicates that the
information is being provided as a relative index into the existing
allocation. Two methods of relative indexing are supported:

* "+n#": A relative index into the allocation referencing the "#"
  node. PRRTE will substitute the "#" node in the allocation

* "+e[:#]": A request for "#" empty nodes — i.e., PRRTE is to
  substitute this reference with nodes that have not yet been used by
  any other app_context. If the ":#" is not provided, PRRTE will
  substitute the reference with all empty nodes. Note that PRRTE does
  track the empty nodes that have been assigned in this manner, so
  multiple uses of this option will result in assignment of unique
  nodes up to the limit of the available empty nodes. Requests for
  more empty nodes than are available will generate an error.

Relative indexing can be combined with absolute naming of hosts in any
arbitrary manner, and can be used in hostfiles as well as with the "--
host" command line option. In addition, any slot specification
provided in hostfiles will be respected — thus, a user can specify
that only a certain number of slots from a relative indexed host are
to be used for a given app context.

Another example may help illustrate this point. Consider the case
where the user has a hostfile containing:

   dummy1 slots=4
   dummy2 slots=4
   dummy3 slots=4
   dummy4 slots=4
   dummy5 slots=4

This may, for example, be a hostfile that describes a set of commonly-
used resources that the user wishes to execute applications against.
For this particular application, the user plans to map byslot, and
wants the first two ranks to be on the second node of any allocation,
the next ranks to land on an empty node, have one rank specifically on
"dummy4", the next rank to be on the second node of the allocation
again, and finally any remaining ranks to be on whatever empty nodes
are left. To accomplish this, the user provides a hostfile of:

   +n2 slots=2
   +e:1
   dummy4 slots=1
   +n2
   +e

The user can now use this information in combination with PRRTE's
sequential mapper to obtain their specific layout:

   <launcher> --hostfile dummyhosts --hostfile mylayout --prtemca rmaps seq ./my_app

which will result in:

   rank0 being mapped to dummy3
   rank1 to dummy1 as the first empty node
   rank2 to dummy4
   rank3 to dummy3
   rank4 to dummy2 and rank5 to dummy5 as the last remaining unused nodes

Note that the sequential mapper ignores the number of slots arguments
as it only maps one rank at a time to each node in the list.

If the default round-robin mapper had been used, then the mapping
would have resulted in:

* ranks 0 and 1 being mapped to dummy3 since two slots were specified

* ranks 2-5 on dummy1 as the first empty node, which has four slots

* rank6 on dummy4 since the hostfile specifies only a single slot from
  that node is to be used

* ranks 7 and 8 on dummy3 since only two slots remain available

* ranks 9-12 on dummy2 since it is the next available empty node and
  has four slots

* ranks 13-16 on dummy5 since it is the last remaining unused node and
  has four slots

Thus, the use of relative indexing can allow for complex mappings to
be ported across allocations, including those obtained from automated
resource managers, without the need for manual manipulation of scripts
and/or command lines.

See the "Host specification" HTML documentation for details about the
format and content of hostfiles.

[machinefile]

Provide a hostfile.  This option is a synonym for "--hostfile"; see
that option for more information.

[host]

Host syntax consists of a comma-delimited list of node names, each
entry optionally containing a ":N" extension indicating the number of
slots to assign to that entry:

   --host node01:5,node02

In the absence of the slot extension, one slot will be assigned to the
node. Duplicate entries are aggregated and the number of slots
assigned to that node are summed together.

Note:

  A "slot" is the PRRTE term for an allocatable unit where we can
  launch a process. Thus, the number of slots equates to the maximum
  number of processes PRRTE may start on that node without
  oversubscribing it.

See the "Host specification" HTML documentation for details about the
format and content of hostfiles.

[personality]

Specify the personality to be used. This governs selection of the
plugin responsible for defining and parsing the command line,
harvesting and forwarding environmental variables, and providing
library-dependent support to the launched processes. Examples include
"ompi" for an application compiled with Open MPI, "mpich" for one
built against the MPICH library, or "oshmem" for an OpenSHMEM
application compiled against SUNY's reference library.

[preload-files]

Syntax: "--preload-files <files>"

Preload the comma separated list of files to the remote machines
current working directory before starting the remote process.

[preload-binary]

Syntax: "--preload-binary"

Preload the binary on the remote machine before starting the remote
process.

[output]

The "output" command line directive must be accompanied by a comma-
delimited list of case-insensitive options that control how output is
generated. The full directive need not be provided — only enough
characters are required to uniquely identify the directive. For
example, "MERGE" is sufficient to represent the "MERGE-STDERR-TO-
STDOUT" directive — while "TAG" can not be used to represent "TAG-
DETAILED" (though "TAG-D" would suffice).

Supported values include:

* "TAG" marks each output line with the "[job,rank]<stream>:" of the
  process that generated it

* "TAG-DETAILED" marks each output line with a detailed annotation
  containing "[namespace,rank][hostname:pid]<stream>:" of the process
  that generated it

* "TAG-FULLNAME" marks each output line with the
  "[namespace,rank]<stream>:" of the process that generated it

* "TAG-FULLNAME" marks each output line with the
  "[namespace,rank]<stream>:" of the process that generated it

* "TIMESTAMP" prefixes each output line with a "[datetime]<stream>:"
  stamp. Note that the timestamp will be the time when the line is
  output by the DVM and not the time when the source output it

* "XML" provides all output in a pseudo-XML format "MERGE-STDERR-TO-
  STDOUT" merges stderr into stdout

* "DIR=DIRNAME" redirects output from application processes into
  "DIRNAME/job/rank/std[out,err,diag]". The provided name will be
  converted to an absolute path

* "FILE=FILENAME" redirects output from application processes into
  "filename.rank." The provided name will be converted to an absolute
  path

Supported qualifiers include "NOCOPY" (do not copy the output to the
stdout/err streams), and "RAW" (do not buffer the output into complete
lines, but instead output it as it is received).

[stdin]

Specify procs to receive stdin [integer ranks, "all", "none"]
(default: "0", indicating rank 0)

[map-by]

Processes are mapped based on one of the following directives as
applied at the job level:

* "SLOT" assigns procs to each node up to the number of available
  slots on that node before moving to the next node in the allocation

* "HWTHREAD" assigns a proc to each hardware thread on a node in a
  round-robin manner up to the number of available slots on that node
  before moving to the next node in the allocation

* "CORE" (default) assigns a proc to each core on a node in a round-
  robin manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "L1CACHE" assigns a proc to each L1 cache on a node in a round-robin
  manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "L2CACHE" assigns a proc to each L2 cache on a node in a round-robin
  manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "L3CACHE" assigns a proc to each L3 cache on a node in a round-robin
  manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "NUMA" assigns a proc to each NUMA region on a node in a round-robin
  manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "PACKAGE" assigns a proc to each package on a node in a round-robin
  manner up to the number of available slots on that node before
  moving to the next node in the allocation

* "NODE" assigns processes in a round-robin fashion to all nodes in
  the allocation, with the number assigned to each node capped by the
  number of available slots on that node

* "SEQ" (often accompanied by the file=<path> qualifier) assigns one
  process to each node specified in the file. The sequential file is
  to contain an entry for each desired process, one per line of the
  file.

* "PPR:N":resource maps N procs to each instance of the specified
  resource type in the allocation

* "RANKFILE" (often accompanied by the file=<path> qualifier) assigns
  one process to the node/resource specified in each entry of the
  file, one per line of the file.

* "PE-LIST=a,b" assigns procs to each node in the allocation based on
  the ORDERED qualifier. The list is comprised of comma-delimited
  ranges of CPUs to use for this job. If the ORDERED qualifier is not
  provided, then each node will be assigned procs up to the number of
  available slots, capped by the availability of the specified CPUs.
  If ORDERED is given, then one proc will be assigned to each of the
  specified CPUs, if available, capped by the number of slots on each
  node and the total number of specified processes. Providing the
  OVERLOAD qualifier to the "bind-to" option removes the check on
  availability of the CPU in both cases.

Any directive can include qualifiers by adding a colon (":") and any
combination of one or more of the following (delimited by colons) to
the "--map-by" option (except where noted):

* "PE=n" bind n CPUs to each process (can not be used in combination
  with rankfile or pe-list directives)

* "SPAN" load balance the processes across the allocation by treating
  the allocation as a single "super-node" (can not be used in
  combination with "slot", "node", "seq", "ppr", "rankfile", or "pe-
  list" directives)

* "OVERSUBSCRIBE" allow more processes on a node than processing
  elements

* "NOOVERSUBSCRIBE" means "!OVERSUBSCRIBE"

* "NOLOCAL" do not launch processes on the same node as "prun"

* "HWTCPUS" use hardware threads as CPU slots

* "CORECPUS" use cores as CPU slots (default)

* "INHERIT" indicates that a child job (i.e., one spawned from within
  an application) shall inherit the placement policies of the parent
  job that spawned it.

* "NOINHERIT" means "`!INHERIT"

* "FILE=<path>" (path to file containing sequential or rankfile
  entries).

* "ORDERED" only applies to the "PE-LIST" option to indicate that
  procs are to be bound to each of the specified CPUs in the order in
  which they are assigned (i.e., the first proc on a node shall be
  bound to the first CPU in the list, the second proc shall be bound
  to the second CPU, etc.)

Note:

  Directives and qualifiers are case-insensitive and can be shortened
  to the minimum number of characters to uniquely identify them. Thus,
  "L1CACHE" can be given as "l1cache" or simply as "L1".

The type of CPU (core vs hwthread) used in the mapping algorithm is
determined as follows:

* by user directive on the command line via the HWTCPUS qualifier to
  the "--map-by" directive

* by setting the "rmaps_default_mapping_policy" MCA parameter to
  include the "HWTCPUS" qualifier. This parameter sets the default
  value for a PRRTE DVM — qualifiers are carried across to DVM jobs
  started via "prun" unless overridden by the user's command line

* defaults to CORE in topologies where core CPUs are defined, and to
  hwthreads otherwise.

If your application uses threads, then you probably want to ensure
that you are either not bound at all (by specifying "--bind-to none"),
or bound to multiple cores using an appropriate binding level or
specific number of processing elements per application process via the
"PE=#" qualifier to the "--map-by" command line directive.

A more detailed description of the mapping, ranking, and binding
procedure can be obtained via the "--help placement" option.

[rank-by]

PRRTE automatically ranks processes for each job starting from zero.
Regardless of the algorithm used, rank assignments span applications
in the same job — i.e., a command line of

   -n 3 app1 : -n 2 app2

will result in "app1" having three processes ranked 0-2 and "app2"
having two processes ranked 3-4.

By default, process ranks are assigned in accordance with the mapping
directive — e.g., jobs that are mapped by-node will have the process
ranks assigned round-robin on a per-node basis. However, users can
override the default by specifying any of the following directives
using the "--rank-by" command line option:

* "SLOT" assigns ranks to each process on a node in the order in which
  the mapper assigned them. This is the default behavior, but is
  provided as an explicit option to allow users to override any
  alternative default specified in the environment. When mapping to a
  specific resource type, procs assigned to a given instance of that
  resource on a node will be ranked on a per-resource basis on that
  node before moving to the next node.

* "NODE" assigns ranks round-robin on a per-node basis

* "FILL" assigns ranks to procs mapped to a particular resource type
  on each node, filling all ranks on that resource before moving to
  the next resource on that node. For example, procs mapped by
  "L1cache" would have all procs on the first "L1cache" ranked
  sequentially before moving to the second "L1cache" on the node. Once
  all procs on the node have been ranked, ranking would continue on
  the next node.

* "SPAN" assigns ranks round-robin to procs mapped to a particular
  resource type, treating the collection of resource instances
  spanning the entire allocation as a single "super node" before
  looping around for the next pass. Thus, ranking would begin with the
  first proc on the first "L1cache" on the first node, then the next
  rank would be assigned to the first proc on the second "L1cache" on
  that node, proceeding across until the first proc had been ranked on
  all "L1cache" used by the job before circling around to rank the
  second proc on each object.

The "rank-by" command line option has no qualifiers.

Note:

  Directives are case-insensitive.  "SPAN" is the same as "span".

A more detailed description of the mapping, ranking, and binding
procedure can be obtained via the "--help placement" option.

[bind-to]

By default, processes are bound to individual CPUs (either COREs or
HWTHREADs, as defined by default or by user specification for the
job). On nodes that are OVERSUBSCRIBEd (i.e., where the number of
procs exceeds the number of assigned slots), the default is to not
bind the processes.

Note:

  Processes from prior jobs that are already executing on a node are
  not "unbound" when a new job mapping results in the node becoming
  oversubscribed.

Binding is performed to the first available specified object type
within the object where the process was mapped. In other words,
binding can only be done to the mapped object or to a resource located
beneath that object.

An object is considered completely consumed when the number of
processes bound to it equals the number of CPUs within it. Unbound
processes are not considered in this computation. Additional processes
cannot be mapped to consumed objects unless the "OVERLOAD" qualifier
is provided via the "--bind-to" command line option.

Note that directives and qualifiers are case-insensitive and can be
shortened to the minimum number of characters to uniquely identify
them. Thus, "L1CACHE" can be given as "l1cache" or simply as "L1".

Supported binding directives include:

* "NONE" does not bind the processes

* "HWTHREAD" binds each process to a single hardware thread/ This
  requires that hwthreads be treated as independent CPUs (i.e., that
  either the "HWTCPUS" qualifier be provided to the "map-by" option or
  that "hwthreads" be designated as CPUs by default).

* "CORE" binds each process to a single core. This can be done whether
  "hwthreads" or "cores" are being treated as independent CPUs
  provided that mapping is performed at the core or higher level.

* "L1CACHE" binds each process to all the CPUs in an "L1" cache.

* "L2CACHE" binds each process to all the CPUs in an "L2" cache

* "L3CACHE" binds each process to all the CPUs in an "L3" cache

* "NUMA" binds each process to all the CPUs in a "NUMA" region

* "PACKAGE" binds each process to all the CPUs in a "PACKAGE"

Any directive can include qualifiers by adding a colon (:) and any
combination of one or more of the following to the "--bind-to" option:

* "OVERLOAD" indicates that objects can have more processes bound to
  them than CPUs within them

* "IF-SUPPORTED" indicates that the job should continue to be launched
  and executed even if binding cannot be performed as requested.

Note:

  Directives and qualifiers are case-insensitive. "OVERLOAD" is the
  same as "overload".

[runtime-options]

The "--runtime-options" command line directive must be accompanied by
a comma-delimited list of case-insensitive options that control the
runtime behavior of the job. The full directive need not be provided —
only enough characters are required to uniquely identify the
directive.

Runtime options are typically "true" or "false", though this is not a
requirement on developers. Since the value of each option may need to
be set (e.g., to override a default set by MCA parameter), the syntax
of the command line directive includes the use of an "=" character to
allow inclusion of a value for the option. For example, one can set
the "ABORT-NONZERO-STATUS" option to "true" by specifying it as
"ABORT-NONZERO-STATUS=1". Note that boolean options can be set to
"true" using a non-zero integer or a case-insensitive string of the
word "true".  For the latter representation, the user need only
provide at least the "T" character. The same policy applies to setting
a boolean option to "false".

Note that a boolean option will default to "true" if provided without
a value. Thus, "--runtime-options abort-nonzero" is sufficient to set
the "ABORT-NONZERO-STATUS" option to "true".

Supported values include:

* "ERROR-NONZERO-STATUS[=(bool)]": if set to false, this directs the
  runtime to treat a process that exits with non-zero status as a
  normal termination.  If set to true, the runtime will consider such
  an occurrence as an error termination and take appropriate action —
  i.e., the job will be terminated unless a runtime option directs
  otherwise. This option defaults to a true value if the option is
  given without a value.

* "DONOTLAUNCH": directs the runtime to map but not launch the
  specified job. This is provided to help explore possible process
  placement patterns before actually starting execution. No value need
  be passed as this is not an option that can be set by default in
  PRRTE.

* "SHOW-PROGRESS[=(bool)]": requests that the runtime provide progress
  reports on its startup procedure — i.e., the launch of its daemons
  in support of a job. This is typically used to debug DVM startup on
  large systems.  This option defaults to a true value if the option
  is given without a value.

* "NOTIFYERRORS[=(bool)]": if set to true, requests that the runtime
  provide a PMIx event whenever a job encounters an error — e.g., a
  process fails.  The event is to be delivered to each remaining
  process in the job. This option defaults to a true value if the
  option is given without a value.  See "--help notifications" for
  more detail as to the PMIx event codes available for capturing
  failure events.

* "RECOVERABLE[=(bool)]": if set to true, this indicates that the
  application wishes to consider the job as recoverable — i.e., the
  application is assuming responsibility for recovering from any
  process failure. This could include application-driven spawn of a
  substitute process or internal compensation for the missing process.
  This option defaults to a true value if the option is given without
  a value.

* "AUTORESTART[=(bool)]": if set to true, this requests that the
  runtime automatically restart failed processes up to "max restarts"
  number of times. This option defaults to a true value if the option
  is given without a value.

* "CONTINUOUS[=(bool)]": if set to true, this informs the runtime that
  the processes in this job are to run until explicitly terminated.
  Processes that fail are to be automatically restarted up to "max
  restarts" number of times. Notification of process failure is to be
  delivered to all processes in the application. This is the
  equivalent of specifying "RECOVERABLE", "NOTIFYERRORS", and
  "AUTORESTART" options except that the runtime, not the application,
  assumes responsibility for process recovery. This option defaults to
  a true value if the option is given without a value.

* "MAX-RESTARTS=<int>": indicates the maximum number of times a given
  process is to be restarted. This can be set at the application or
  job level (which will then apply to all applications in that job).

* "EXEC-AGENT=<path>" indicates the executable that shall be used to
  start an application process. The resulting command for starting an
  application process will be "<path> app <app-argv>". The path may
  contain its own command line arguments.

* "DEFAULT-EXEC-AGENT": directs the runtime to use the system default
  exec agent to start an application process. No value need be passed
  as this is not an option that can be set by default in PRRTE.

* "OUTPUT-PROCTABLE[(=channel)]": directs the runtime to report the
  convential debugger process table (includes PID and host location of
  each process in the application). Output is directed to stdout if
  the channel is "-", stderr if "+", or into the specified file
  otherwise. If no channel is specified, output will be directed to
  stdout.

* "STOP-ON-EXEC": directs the runtime to stop the application
  process(es) immediately upon exec'ing them. The directive will apply
  to all processes in the job.

* "STOP-IN-INIT": indicates that the runtime should direct the
  application process(es) to stop in "PMIx_Init()". The directive will
  apply to all processes in the job.

* "STOP-IN-APP": indicates that the runtime should direct application
  processes to stop at some application-defined place and notify they
  are ready-to-debug. The directive will apply to all processes in the
  job.

* "TIMEOUT=<string>": directs the runtime to terminate the job after
  it has executed for the specified time. Time is specified in colon-
  delimited format — e.g., "01:20:13:05" to indicate 1 day, 20 hours,
  13 minutes and 5 seconds. Time specified without colons will be
  assumed to have been given in seconds.

* "SPAWN-TIMEOUT=<string>": directs the runtime to terminate the job
  if job launch is not completed within the specified time. Time is
  specified in colon-delimited format — e.g., "01:20:13:05" to
  indicate 1 day, 20 hours, 13 minutes and 5 seconds.  Time specified
  without colons will be assumed to have been given in seconds.

* "REPORT-STATE-ON-TIMEOUT[(=bool)]": directs the runtime to provide a
  detailed report on job and application process state upon job
  timeout. This option defaults to a true value if the option is given
  without a value.

* "GET-STACK-TRACES[(=bool)]": requests that the runtime provide stack
  traces on all application processes still executing upon timeout.
  This option defaults to a true value if the option is given without
  a value.

* "REPORT-CHILD-JOBS-SEPARATELY[(=bool)]": directs the runtime to
  report the exit status of any child jobs spawned by the primary job
  separately. If false, then the final exit status reported will be
  zero if the primary job and all spawned jobs exit normally, or the
  first non-zero status returned by either primary or child jobs. This
  option defaults to a true value if the option is given without a
  value.

* "AGGREGATE-HELP-MESSAGES[(=bool)]": directs the runtime to aggregate
  help messages, reporting each unique help message once accompanied
  by the number of processes that reported it. This option defaults to
  a true value if the option is given without a value.

* "FWD-ENVIRONMENT[(=bool)]": directs the runtime to forward the
  entire local environment in support of the application. This option
  defaults to a true value if the option is given without a value.

The "--runtime-options" command line option has no qualifiers.

Note:

  Directives are case-insensitive.  "FWD-ENVIRONMENT" is the same as
  "fwd-environment".

[rankfile]

Name of file to specify explicit task mapping [display]

The "display" command line directive must be accompanied by a comma-
delimited list of case-insensitive options indicating what information
about the job and/or allocation is to be displayed. The full directive
need not be provided — only enough characters are required to uniquely
identify the directive. For example, "ALL" is sufficient to represent
the "ALLOCATION" directive — while "MAP" can not be used to represent
"MAP-DEVEL" (though "MAP-D" would suffice).

Supported values include:

* "ALLOCATION" displays the detected hosts and slot assignments for
  this job

* "BINDINGS" displays the resulting bindings applied to processes in
  this job

* "MAP" displays the resulting locations assigned to processes in this
  job

* "MAP-DEVEL" displays a more detailed report on the locations
  assigned to processes in this job that includes local and node
  ranks, assigned bindings, and other data

* "TOPO=LIST" displays the topology of each node in the semicolon-
  delimited list that is allocated to the job

* "CPUS[=LIST]" displays the available CPUs on the provided semicolon-
  delimited list of nodes (defaults to all nodes)

The display command line directive can include qualifiers by adding a
colon (":") and any combination of one or more of the following
(delimited by colons):

* "PARSEABLE" directs that the output be provided in a format that is
  easily parsed by machines. Note that "PARSABLE" is also accepted as
  a typical spelling for the qualifier.

Provided qualifiers will apply to *all* of the display directives.

[do-not-launch]

Perform all necessary operations to prepare to launch the application,
but do not actually launch it (usually used to test mapping patterns)

[mca]

Syntax: "--mca <key> <value>", where "key" is the parameter name and
"value" is the parameter value.

Pass generic MCA parameters — i.e., parameters whose project
affiliation must be determined by PRRTE based on matching the name of
the parameter with defined values from various projects that PRRTE
knows about.

Deprecated: This translation can be incomplete (e.g., if a project
adds or changes parameters) — thus, it is strongly recommended that
users use project-specific parameters such as "--prtemca" or "--
pmixmca".

[gmca]

Syntax: "--gmca <key> <value>", where "key" is the parameter name and
"value" is the parameter value. The "g" prefix indicates that this
parameter is "global", and to be applied to *all* application contexts
— not just the one in which the directive appears.

Pass generic MCA parameters — i.e., parameters whose project
affiliation must be determined by PRRTE based on matching the name of
the parameter with defined values from various projects that PRRTE
knows about.

Deprecated: This translation can be incomplete (e.g., if known project
adds or changes parameters) — thus, it is strongly recommended that
users use project-specific parameters such as "--gprtemca" or "--
gpmixmca".

[xml]

Provide all output in XML format.

Deprecated: This option is deprecated.  Please use "--output".

[bind-to-core]

Bind each process to its own core.

Deprecated: This option is deprecated.  Please use "--bind-to core".

[tag-output]

Tag all output with "[job,rank]".

Deprecated: This option is deprecated.  Please use "--output".

[timestamp-output]

Timestamp all application process output.

Deprecated: This option is deprecated.  Please use "--output
timestamp".

[output-directory]

Redirect output from application processes into
"filename/job/rank/std[out,err,diag]". A relative path value will be
converted to an absolute path. The directory name may include a colon
followed by a comma-delimited list of optional case-insensitive
directives. Supported directives currently include "NOJOBID" (do not
include a job-id directory level) and "NOCOPY" (do not copy the output
to the stdout/err streams).

Deprecated: This option is deprecated.  Please use "--output
dir=<path>".

[output-filename]

Redirect output from application processes into "filename.rank". A
relative path value will be converted to an absolute path. The
directory name may include a colon followed by a comma-delimited list
of optional case-insensitive directives. Supported directives
currently include "NOCOPY" (do not copy the output to the stdout/err
streams).

Deprecated: This option is deprecated.  Please use "--output
file=<path>"

[merge-stderr-to-stdout]

Merge stderr to stdout for each process.

Deprecated: This option is deprecated.  Please use "--output merge"

[display-devel-map]

Display a detailed process map (mostly intended for developers) just
before launch.

Deprecated: This option is deprecated.  Please use "--display map-
devel".

[display-topo]

Display the topology as part of the process map (mostly intended for
developers) just before launch.

Deprecated: This option is deprecated.  Please use "--display topo".

[report-bindings]

Display process bindings to stderr.

Deprecated: This option is deprecated.  Please use "--display
bindings".

[display-devel-allocation]

Display a detailed list (mostly intended for developers) of the
allocation being used by this job.

Deprecated: This option is deprecated.  Please use "--display alloc-
devel".

[display-map]

Display the process map just before launch.

Deprecated: This option is deprecated.  Please use "--display map".

[display-allocation]

Display the allocation being used by this job.

Deprecated: This option is deprecated.  Please use "--display alloc".

[placement]


Overview
--------

PRRTE provides a set of three controls for assigning process locations
and ranks:

1. Mapping: Assigns a default location to each process

2. Ranking: Assigns a unique integer rank value to each process

3. Binding: Constrains each process to run on specific processors

This section provides an overview of these three controls.  Unless
otherwise this behavior is shared by "prun(1)" (working with a PRRTE
DVM), and "prterun(1)". More detail about PRRTE process placement is
available in the following sections (using "--help
placement-<section>"):

* "examples": some examples of the interactions between mapping,
  ranking, and binding options.

* "fundamentals": provides deeper insight into PRRTE's mapping,
  ranking, and binding options.

* "limits": explains the difference between *overloading* and
  *oversubscribing* resources.

* "diagnostics": describes options for obtaining various diagnostic
  reports that aid the user in verifying and tuning the placement for
  a specific job.

* "rankfiles": explains the format and use of the rankfile mapper for
  specifying arbitrary process placements.

* "deprecated": a list of deprecated options and their new
  equivalents.

* "all": outputs all the placement help except for the "deprecated"
  section.


Quick Summary
=============

The two binaries that most influence process layout are "prte(1)" and
"prun(1)".  The "prte(1)" process discovers the allocation,
establishes a Distributed Virtual Machine by starting a "prted(1)"
daemon on each node of the allocation, and defines the efault
mapping/ranking/binding policies for all jobs.  The "prun(1)" process
defines the specific mapping/ranking/binding for a specific job. Most
of the command line controls are targeted to "prun(1)" since each job
has its own unique requirements.

"prterun(1)" is just a wrapper around "prte(1)" for a single job PRRTE
DVM. It is doing the job of both "prte(1)" and "prun(1)", and, as
such, accepts the sum all of their command line arguments. Any example
that uses "prun(1)" can substitute the use of "prterun(1)" except
where otherwise noted.

The "prte(1)" process attempts to automatically discover the nodes in
the allocation by querying supported resource managers. If a supported
resource manager is not present then "prte(1)" relies on a hostfile
provided by the user.  In the absence of such a hostfile it will run
all processes on the localhost.

If running under a supported resource manager, the "prte(1)" process
will start the daemon processes ("prted(1)") on the remote nodes using
the corresponding resource manager process starter. If no such starter
is available then "ssh" (or "rsh") is used.

Minus user direction, PRRTE will automatically map processes in a
round-robin fashion by CPU, binding each process to its own CPU. The
type of CPU used (core vs hwthread) is determined by (in priority
order):

* user directive on the command line via the HWTCPUS qualifier to the
  "--map-by" directive

* setting the "rmaps_default_mapping_policy" MCA parameter to include
  the "HWTCPUS" qualifier. This parameter sets the default value for a
  PRRTE DVM — qualifiers are carried across to DVM jobs started via
  "prun" unless overridden by the user's command line

* defaulting to "CORE" in topologies where core CPUs are defined, and
  to "hwthreads" otherwise.

By default, the ranks are assigned in accordance with the mapping
directive — e.g., jobs that are mapped by-node will have the process
ranks assigned round-robin on a per-node basis.

PRRTE automatically binds processes unless directed not to do so by
the user. Minus direction, PRRTE will bind individual processes to
their own CPU within the object to which they were mapped. Should a
node become oversubscribed during the mapping process, and if
oversubscription is allowed, all subsequent processes assigned to that
node will *not* be bound.


Definition of 'slot'
--------------------

The term "slot" is used extensively in the rest of this documentation.
A slot is an allocation unit for a process.  The number of slots on a
node indicate how many processes can potentially execute on that node.
By default, PRRTE will allow one process per slot.

If PRRTE is not explicitly told how many slots are available on a node
(e.g., if a hostfile is used and the number of slots is not specified
for a given node), it will determine a maximum number of slots for
that node in one of two ways:

1. Default behavior: By default, PRRTE will attempt to discover the
   number of processor cores on the node, and use that as the number
   of slots available.

2. When "--use-hwthread-cpus" is used: If "--use-hwthread-cpus" is
   specified on the command line, then PRRTE will attempt to discover
   the number of hardware threads on the node, and use that as the
   number of slots available.

This default behavior also occurs when specifying the "--host" option
with a single host.  Thus, the command:

   shell$ prun --host node1 ./a.out

launches a number of processes equal to the number of cores on node
"node1", whereas:

   shell$ prun --host node1 --use-hwthread-cpus ./a.out

launches a number of processes equal to the number of hardware threads
on "node1".

When PRRTE applications are invoked in an environment managed by a
resource manager (e.g., inside of a Slurm job), and PRRTE was built
with appropriate support for that resource manager, then PRRTE will be
informed of the number of slots for each node by the resource manager.
For example:

   shell$ prun ./a.out

launches one process for every slot (on every node) as dictated by the
resource manager job specification.

Also note that the one-process-per-slot restriction can be overridden
in unmanaged environments (e.g., when using hostfiles without a
resource manager) if oversubscription is enabled (by default, it is
disabled).  Most parallel applications and HPC environments do not
oversubscribe; for simplicity, the majority of this documentation
assumes that oversubscription is not enabled.


Slots are not hardware resources
================================

Slots are frequently incorrectly conflated with hardware resources. It
is important to realize that slots are an entirely different metric
than the number (and type) of hardware resources available.

Here are some examples that may help illustrate the difference:

1. More processor cores than slots: Consider a resource manager job
   environment that tells PRRTE that there is a single node with 20
   processor cores and 2 slots available.  By default, PRRTE will only
   let you run up to 2 processes.

   Meaning: you run out of slots long before you run out of processor
   cores.

2. More slots than processor cores: Consider a hostfile with a single
   node listed with a "slots=50" qualification.  The node has 20
   processor cores.  By default, PRRTE will let you run up to 50
   processes.

   Meaning: you can run many more processes than you have processor
   cores.


Definition of "processor element"
---------------------------------

By default, PRRTE defines that a "processing element" is a processor
core.  However, if "--use-hwthread-cpus" is specified on the command
line, then a "processing element" is a hardware thread.

[placement-examples]


Examples
--------

Listed here are the subset of command line options that will be used
in the process mapping/ranking/binding examples below.


Specifying Host Nodes
=====================

Use one of the following options to specify which hosts (nodes) within
the PRRTE DVM environment to run on.

   --host <host1,host2,...,hostN>

   # or

   --host <host1:X,host2:Y,...,hostN:Z>

* List of hosts on which to invoke processes. After each hostname a
  colon (":") followed by a positive integer can be used to specify
  the number of slots on that host (":X", ":Y", and ":Z"). The default
  is "1".

   --hostfile <hostfile>

* Provide a hostfile to use.


Process Mapping / Ranking / Binding Options
===========================================

* "-c #", "-n #", "--n #", "--np <#>": Run this many copies of the
  program on the given nodes. This option indicates that the specified
  file is an executable program and not an application context. If no
  value is provided for the number of copies to execute (i.e., neither
  the "-np" nor its synonyms are provided on the command line), "prun"
  will automatically execute a copy of the program on each process
  slot (see below for description of a "process slot"). This feature,
  however, can only be used in the SPMD model and will return an error
  (without beginning execution of the application) otherwise.

  Note:

    These options specify the number of processes to launch. None of
    the options imply a particular binding policy — e.g., requesting
    "N" processes for each package does not imply that the processes
    will be bound to the package.

* "--map-by <object>": Map to the specified object. Supported objects
  include:

  * "slot"

  * "hwthread"

  * "core" (default)

  * "l1cache"

  * "l2cache"

  * "l3cache"

  * "numa"

  * "package"

  * "node"

  * "seq"

  * "ppr"

  * "rankfile"

  * "pe-list"

  Any object can include qualifiers by adding a colon (":") and any
  colon-delimited combination of one or more of the following to the "
  --map-by" options:

  * "PE=n" bind "n" processing elements to each process (can not be
    used in combination with rankfile or pe-list directives)

    Error:

      JMS Several of the options below refer to "pe-list". Is this
      option supposed to be "PE-LIST=n", not "PE=n"?

  * "SPAN" load balance the processes across the allocation (cannot be
    used in combination with "slot", "node", "seq", "ppr", "rankfile",
    or "pe-list" directives)

  * "OVERSUBSCRIBE" allow more processes on a node than processing
    elements

  * "NOOVERSUBSCRIBE" means "!OVERSUBSCRIBE"

  * "NOLOCAL" do not launch processes on the same node as "prun"

  * "HWTCPUS" use hardware threads as CPU slots

  * "CORECPUS" use cores as CPU slots (default)

  * "INHERIT" indicates that a child job (i.e., one spawned from
    within an application) shall inherit the placement policies of the
    parent job that spawned it.

  * "NOINHERIT" means "!INHERIT"

  * "FILE=<path>" (path to file containing sequential or rankfile
    entries).

  * "ORDERED" only applies to the PE-LIST option to indicate that
    procs are to be bound to each of the specified CPUs in the order
    in which they are assigned (i.e., the first proc on a node shall
    be bound to the first CPU in the list, the second proc shall be
    bound to the second CPU, etc.)

  "ppr" policy example: "--map-by ppr:N:<object>" will launch "N"
  times the number of objects of the specified type on each node.

  Note:

    Directives and qualifiers are case-insensitive and can be
    shortened to the minimum number of characters to uniquely identify
    them. Thus, "L1CACHE" can be given as "l1cache" or simply as "L1".

* "--rank-by <object>": This assigns ranks in round-robin fashion
  according to the specified object. The default follows the mapping
  pattern. Supported rank-by objects include:

  * "slot"

  * "node"

  * "fill"

  * "span"

  There are no qualifiers for the "--rank-by" directive.

* "--bind-to <object>": This binds processes to the specified object.
  See defaults in Quick Summary.  Supported bind-to objects include:

  * "none"

  * "hwthread"

  * "core"

  * "l1cache"

  * "l2cache"

  * "l3cache"

  * "numa"

  * "package"

  Any object can include qualifiers by adding a colon (":") and any
  colon-delimited combination of one or more of the following to the "
  --bind-to" options:

  * "overload-allowed" allows for binding more than one process in
    relation to a CPU

  * "if-supported" if binding to that object is supported on this
    system.


Specifying Host Nodes
=====================

Host nodes can be identified on the command line with the "--host"
option or in a hostfile.

For example, assuming no other resource manager or scheduler is
involved:

   prun --host aa,aa,bb ./a.out

This launches two processes on node "aa" and one on "bb".

   prun --host aa ./a.out

This launches one process on node "aa".

   prun --host aa:5 ./a.out

This launches five processes on node "aa".

Or, consider the hostfile:

   $ cat myhostfile
   aa slots=2
   bb slots=2
   cc slots=2

Here, we list both the host names ("aa", "bb", and "cc") but also how
many "slots" there are for each. Slots indicate how many processes can
potentially execute on a node. For best performance, the number of
slots may be chosen to be the number of cores on the node or the
number of processor sockets.

If the hostfile does not provide slots information, the PRRTE DVM will
attempt to discover the number of cores (or hwthreads, if the
":HWTCPUS" qualifier to the "--map-by" option is set) and set the
number of slots to that value.

Examples using the hostfile above with and without the "--host"
option:

   prun --hostfile myhostfile ./a.out

This will launch two processes on each of the three nodes.

   prun --hostfile myhostfile --host aa ./a.out

This will launch two processes, both on node "aa".

   prun --hostfile myhostfile --host dd ./a.out

This will find no hosts to run on and abort with an error. That is,
the specified host "dd" is not in the specified hostfile.

When running under resource managers (e.g., SLURM, Torque, etc.), PRTE
will obtain both the hostnames and the number of slots directly from
the resource manger. The behavior of "--host" in that environment will
behave the same as if a hostfile was provided (since it is provided by
the resource manager).


Specifying Number of Processes
==============================

As we have just seen, the number of processes to run can be set using
the hostfile. Other mechanisms exist.

The number of processes launched can be specified as a multiple of the
number of nodes or processor sockets available. Consider the hostfile
below for the examples that follow.

   $ cat myhostfile
   aa
   bb

For example:

   prun --hostfile myhostfile --map-by ppr:2:package ./a.out

This launches processes 0-3 on node "aa" and process 4-7 on node "bb",
where "aa" and "bb" are both dual-package nodes. The "--map-by
ppr:2:package" option also turns on the "--bind-to package" option,
which is discussed in a later section.

   prun --hostfile myhostfile --map-by ppr:2:node ./a.out

This launches processes 0-1 on node "aa" and processes 2-3 on node
"bb".

   prun --hostfile myhostfile --map-by ppr:1:node ./a.out

This launches one process per host node.

Another alternative is to specify the number of processes with the "--
np" option. Consider now the hostfile:

   $ cat myhostfile
   aa slots=4
   bb slots=4
   cc slots=4

With this hostfile:

   prun --hostfile myhostfile --np 6 ./a.out

This will launch processes 0-3 on node "aa" and processes 4-5 on node
"bb".  The remaining slots in the hostfile will not be used since the
"-np" option indicated that only 6 processes should be launched.


Mapping Processes to Nodes Using Policies
=========================================

The examples above illustrate the default mapping of process processes
to nodes. This mapping can also be controlled with various "prun" /
"prterun" options that describe mapping policies.

   $ cat myhostfile
   aa slots=4
   bb slots=4
   cc slots=4

Consider the hostfile above, with "--np 6":

+---------------------------+---------------------------+---------------------------+---------------------------+
| Command                   | Ranks on "aa"             | Ranks on "bb"             | Ranks on "cc"             |
|===========================|===========================|===========================|===========================|
| "prun"                    | 0 1 2 3                   | 4 5                       |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| "prun --map-by node"      | 0 3                       | 1 4                       | 2 5                       |
+---------------------------+---------------------------+---------------------------+---------------------------+
| "prun --map-by            |                           | 0 2 4                     | 1 3 5                     |
| node:NOLOCAL"             |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+

The "--map-by node" option will load balance the processes across the
available nodes, numbering each process by node in a round-robin
fashion.

The ":NOLOCAL" qualifier to "--map-by" prevents any processes from
being mapped onto the local host (in this case node "aa"). While
"prun" typically consumes few system resources, the ":NOLOCAL"
qualifier can be helpful for launching very large jobs where "prun"
may actually need to use noticeable amounts of memory and/or
processing time.

Just as "--np" can specify fewer processes than there are slots, it
can also oversubscribe the slots. For example, with the same hostfile:

   prun --hostfile myhostfile --np 14 ./a.out

This will produce an error since the default ":NOOVERSUBSCRIBE"
qualifier to "--map-by" prevents oversubscription.

To oversubscribe the nodes you can use the ":OVERSUBSCRIBE" qualifier
to "--map-by":

   prun --hostfile myhostfile --np 14 --map-by :OVERSUBSCRIBE ./a.out

This will launch processes 0-5 on node "aa", 6-9 on "bb", and 10-13 on
"cc".

Limits to oversubscription can also be specified in the hostfile
itself with the "max_slots" field:

   $ cat myhostfile
   aa slots=4 max_slots=4
   bb         max_slots=8
   cc slots=4

The "max_slots" field specifies such a limit. When it does, the
"slots" value defaults to the limit. Now:

   prun --hostfile myhostfile --np 14 --map-by :OVERSUBSCRIBE ./a.out

This causes the first 12 processes to be launched as before, but the
remaining two processes will be forced onto node cc. The other two
nodes are protected by the hostfile against oversubscription by this
job.

Using the ":NOOVERSUBSCRIBE" qualifier to "--map-by" option can be
helpful since the PRTE DVM currently does not get "max_slots" values
from the resource manager.

Of course, "--np" can also be used with the "--host" option. For
example,

   prun --host aa,bb --np 8 ./a.out

This will produce an error since the default ":NOOVERSUBSCRIBE"
qualifier to "--map-by" prevents oversubscription.

   prun --host aa,bb --np 8 --map-by :OVERSUBSCRIBE ./a.out

This launches 8 processes. Since only two hosts are specified, after
the first two processes are mapped, one to "aa" and one to "bb", the
remaining processes oversubscribe the specified hosts evenly.

   prun --host aa:2,bb:6 --np 8 ./a.out

This launches 8 processes. Processes 0-1 on node "aa" since it has 2
slots and processes 2-7 on node "bb" since it has 6 slots.

And here is a MIMD example:

   prun --host aa --np 1 hostname : --host bb,cc --np 2 uptime

This will launch process 0 running "hostname" on node "aa" and
processes 1 and 2 each running "uptime" on nodes "bb" and "cc",
respectively.

[placement-rankfiles]


Rankfiles
---------

Another way to specify arbitrary mappings is with a rankfile, which
gives you detailed control over process binding as well.

Rankfiles are text files that specify detailed information about how
individual processes should be mapped to nodes, and to which
processor(s) they should be bound. Each line of a rankfile specifies
the location of one process. The general form of each line in the
rankfile is:

   rank <N>=<hostname> slot=<slot list>

For example:

   $ cat myrankfile
   rank 0=aa slot=10-12
   rank 1=bb slot=0,1,4
   rank 2=cc slot=1-2
   $ prun --host aa,bb,cc,dd --map-by rankfile:FILE=myrankfile ./a.out

Means that:

* Rank 0 runs on node aa, bound to logical cores 10-12.

* Rank 1 runs on node bb, bound to logical cores 0, 1, and 4.

* Rank 2 runs on node cc, bound to logical cores 1 and 2.

Similarly:

   $ cat myrankfile
   rank 0=aa slot=1:0-2
   rank 1=bb slot=0:0,1,4
   rank 2=cc slot=1-2
   $ prun --host aa,bb,cc,dd --map-by rankfile:FILE=myrankfile ./a.out

Means that:

* Rank 0 runs on node aa, bound to logical package 1, cores 10-12 (the
  0th through 2nd cores on that package).

* Rank 1 runs on node bb, bound to logical package 0, cores 0, 1, and
  4.

* Rank 2 runs on node cc, bound to logical cores 1 and 2.

The hostnames listed above are "absolute," meaning that actual
resolvable hostnames are specified. However, hostnames can also be
specified as "relative," meaning that they are specified in relation
to an externally-specified list of hostnames (e.g., by "prun"'s "--
host" argument, a hostfile, or a job scheduler).

The "relative" specification is of the form ""+n<X>"", where "X" is an
integer specifying the Xth hostname in the set of all available
hostnames, indexed from 0. For example:

   $ cat myrankfile
   rank 0=+n0 slot=10-12
   rank 1=+n1 slot=0,1,4
   rank 2=+n2 slot=1-2
   $ prun --host aa,bb,cc,dd --map-by rankfile:FILE=myrankfile ./a.out

All package/core slot locations are be specified as *logical* indexes.
You can use tools such as HWLOC's "lstopo" to find the logical indexes
of packages and cores.

[placement-deprecated]


Deprecated options
------------------

These deprecated options will be removed in a future release.

+----------------------+----------------------+--------------------------------+
| Deprecated Option    | Replacement          | Description                    |
|======================|======================|================================|
| "--bind-to-core"     | "--bind-to core"     | Bind processes to cores        |
+----------------------+----------------------+--------------------------------+
| "--bind-to-socket"   | "--bind-to package"  | Bind processes to processor    |
|                      |                      | sockets                        |
+----------------------+----------------------+--------------------------------+
| "--bycore"           | "--map-by core"      | Map processes by core          |
+----------------------+----------------------+--------------------------------+
| "--bynode"           | "--map-by node"      | Launch processes one per node, |
|                      |                      | cycling by node in a round-    |
|                      |                      | robin fashion. This spreads    |
|                      |                      | processes evenly among nodes   |
|                      |                      | and assigns ranks in a round-  |
|                      |                      | robin, "by node" manner.       |
+----------------------+----------------------+--------------------------------+
| "--byslot"           | "--map-by slot"      | Map and rank processes round-  |
|                      |                      | robin by slot                  |
+----------------------+----------------------+--------------------------------+
| "--cpus-per-proc     | *--map-by <obj>:PE=  | Bind each process to the       |
| <#perproc>"          | <#perproc>`*         | specified number of CPUs       |
+----------------------+----------------------+--------------------------------+
| "--cpus-per-rank     | "--map-by            | Alias for "--cpus-per-proc"    |
| <#perrank>"          | <obj>:PE=<#perrank>" |                                |
+----------------------+----------------------+--------------------------------+
| "--display-          | "--display ALLOC"    | Display the detected resource  |
| allocation"          |                      | allocation                     |
+----------------------+----------------------+--------------------------------+
| "-display-devel-map" | "--display MAP-      | Display a detailed process map |
|                      | DEVEL"               | (mostly intended for           |
|                      |                      | developers) just before        |
|                      |                      | launch.                        |
+----------------------+----------------------+--------------------------------+
| "--display-map"      | "--display MAP"      | Display a table showing the    |
|                      |                      | mapped location of each        |
|                      |                      | process prior to launch.       |
+----------------------+----------------------+--------------------------------+
| "--display-topo"     | "--display TOPO"     | Display the topology as part   |
|                      |                      | of the process map (mostly     |
|                      |                      | intended for developers) just  |
|                      |                      | before launch.                 |
+----------------------+----------------------+--------------------------------+
| "--do-not-launch"    | "--map-by            | Perform all necessary          |
|                      | :DONOTLAUNCH"        | operations to prepare to       |
|                      |                      | launch the application, but do |
|                      |                      | not actually launch it         |
|                      |                      | (usually used to test mapping  |
|                      |                      | patterns).                     |
+----------------------+----------------------+--------------------------------+
| "--do-not-resolve"   | "--map-by            | Do not attempt to resolve      |
|                      | :DONOTRESOLVE"       | interfaces — usually used to   |
|                      |                      | determine proposed process     |
|                      |                      | placement/binding prior to     |
|                      |                      | obtaining an allocation.       |
+----------------------+----------------------+--------------------------------+
| "-N <num>"           | "--map-by            | Launch "num" processes per     |
|                      | prr:<num>:node"      | node on all allocated nodes    |
+----------------------+----------------------+--------------------------------+
| "--nolocal"          | "--map-by :NOLOCAL"  | Do not run any copies of the   |
|                      |                      | launched application on the    |
|                      |                      | same node as "prun" is         |
|                      |                      | running. This option will      |
|                      |                      | override listing the           |
|                      |                      | "localhost" with "--host" or   |
|                      |                      | any other host-specifying      |
|                      |                      | mechanism.                     |
+----------------------+----------------------+--------------------------------+
| "--nooversubscribe"  | "--map-by            | Do not oversubscribe any       |
|                      | :NOOVERSUBSCRIBE"    | nodes; error (without starting |
|                      |                      | any processes) if the          |
|                      |                      | requested number of processes  |
|                      |                      | would cause oversubscription.  |
|                      |                      | This option implicitly sets    |
|                      |                      | "max_slots" equal to the       |
|                      |                      | "slots" value for each node.   |
|                      |                      | (Enabled by default).          |
+----------------------+----------------------+--------------------------------+
| "--npernode          | "--map-by            | On each node, launch this many |
| <#pernode>"          | ppr:<#pernode>:node" | processes                      |
+----------------------+----------------------+--------------------------------+
| "--npersocket        | "--map-by ppr:<#per  | On each node, launch this many |
| <#persocket>"        | package>:package"    | processes times the number of  |
|                      |                      | processor sockets on the node. |
|                      |                      | The "--npersocket" option also |
|                      |                      | turns on the "-- bind-to       |
|                      |                      | socket" option. The term       |
|                      |                      | "socket" has been globally     |
|                      |                      | replaced with "package".       |
+----------------------+----------------------+--------------------------------+
| "--oversubscribe"    | "--map-by            | Nodes are allowed to be        |
|                      | :OVERSUBSCRIBE"      | oversubscribed, even on a      |
|                      |                      | managed system, and            |
|                      |                      | overloading of processing      |
|                      |                      | elements.                      |
+----------------------+----------------------+--------------------------------+
| "--pernode"          | "--map-by            | On each node, launch one       |
|                      | ppr:1:node"          | process                        |
+----------------------+----------------------+--------------------------------+
| "--ppr"              | *--map-by            | Comma-separated list of number |
|                      | ppr:<list>`*         | of processes on a given        |
|                      |                      | resource type [default:        |
|                      |                      | "none"].                       |
+----------------------+----------------------+--------------------------------+
| "--rankfile          | "--map-by rankfile:  | Use a rankfile for             |
| <FILENAME>"          | FILE=<FILENAME>"     | mapping/ranking/binding        |
+----------------------+----------------------+--------------------------------+
| "--report-bindings"  | "--display BINDINGS" | Report any bindings for        |
|                      |                      | launched processes             |
+----------------------+----------------------+--------------------------------+
| "--tag-output"       | "--output TAG"       | Tag all output with            |
|                      |                      | "[job,rank]"                   |
+----------------------+----------------------+--------------------------------+
| "--timestamp-output" | "--output TIMESTAMP" | Timestamp all application      |
|                      |                      | process output                 |
+----------------------+----------------------+--------------------------------+
| "--use-hwthread-     | "--map-by :HWTCPUS"  | Use hardware threads as        |
| cpus"                |                      | independent CPUs               |
+----------------------+----------------------+--------------------------------+
| "--xml"              | "--output XML"       | Provide all output in XML      |
|                      |                      | format                         |
+----------------------+----------------------+--------------------------------+

[placement-diagnostics]


Diagnostics
-----------

PRRTE provides various diagnostic reports that aid the user in
verifying and tuning the mapping/ranking/binding for a specific job.

The ":REPORT" qualifier to the "--bind-to" command line option can be
used to report process bindings.

As an example, consider a node with:

* 2 processor packages,

* 4 cores per package, and

* 8 hardware threads per core.

In each of the examples below the binding is reported in a human
readable format.

   $ prun --np 4 --map-by core --bind-to core:REPORT ./a.out
   [node01:103137] MCW rank 0 bound to package[0][core:0]
   [node01:103137] MCW rank 1 bound to package[0][core:1]
   [node01:103137] MCW rank 2 bound to package[0][core:2]
   [node01:103137] MCW rank 3 bound to package[0][core:3]

In the example above, processes are bound to successive cores on the
first package.

   $ prun --np 4 --map-by package --bind-to package:REPORT ./a.out
   [node01:103115] MCW rank 0 bound to package[0][core:0-9]
   [node01:103115] MCW rank 1 bound to package[1][core:10-19]
   [node01:103115] MCW rank 2 bound to package[0][core:0-9]
   [node01:103115] MCW rank 3 bound to package[1][core:10-19]

In the example above, processes are bound to all cores on successive
packages in a round-robin fashion.

   $ prun --np 4 --map-by package:PE=2 --bind-to core:REPORT ./a.out
   [node01:103328] MCW rank 0 bound to package[0][core:0-1]
   [node01:103328] MCW rank 1 bound to package[1][core:10-11]
   [node01:103328] MCW rank 2 bound to package[0][core:2-3]
   [node01:103328] MCW rank 3 bound to package[1][core:12-13]

The example above shows us that 2 cores have been bound per process.
The ":PE=2" qualifier states that 2 CPUs underneath the package (which
would be cores in this case) are mapped to each process.

   $ prun --np 4 --map-by core:PE=2:HWTCPUS --bind-to :REPORT  hostname
   [node01:103506] MCW rank 0 bound to package[0][hwt:0-1]
   [node01:103506] MCW rank 1 bound to package[0][hwt:8-9]
   [node01:103506] MCW rank 2 bound to package[0][hwt:16-17]
   [node01:103506] MCW rank 3 bound to package[0][hwt:24-25]

The example above shows us that 2 hardware threads have been bound per
process.  In this case "prun" is directing the DVM to map by hardware
threads since we used the ":HWTCPUS" qualifier. Without that qualifier
this command would return an error since by default the DVM will not
map to resources smaller than a core.  The ":PE=2" qualifier states
that 2 processing elements underneath the core (which would be
hardware threads in this case) are mapped to each process.

   $ prun --np 4 --bind-to none:REPORT  hostname
   [node01:107126] MCW rank 0 is not bound (or bound to all available processors)
   [node01:107126] MCW rank 1 is not bound (or bound to all available processors)
   [node01:107126] MCW rank 2 is not bound (or bound to all available processors)
   [node01:107126] MCW rank 3 is not bound (or bound to all available processors)

Binding is turned off in the above example, as reported.

[placement-fundamentals]


Fundamentals
------------

The mapping of processes to nodes can be defined not just with general
policies but also, if necessary, using arbitrary mappings that cannot
be described by a simple policy. Supported directives, given on the
command line via the "--map-by" option, include:

* "SEQ": (often accompanied by the "file=<path>" qualifier) assigns
  one process to each node specified in the file. The sequential file
  is to contain an entry for each desired process, one per line of the
  file.

* "RANKFILE": (often accompanied by the "file=<path>" qualifier)
  assigns one process to the node/resource specified in each entry of
  the file, one per line of the file.

For example, using the hostfile below:

   $ cat myhostfile
   aa slots=4
   bb slots=4
   cc slots=4

The command below will launch three processes, one on each of nodes
"aa", "bb", and "cc", respectively. The slot counts don't matter; one
process is launched per line on whatever node is listed on the line.

   $ prun --hostfile myhostfile --map-by seq ./a.out

Impact of the ranking option is best illustrated by considering the
following hostfile and test cases where each node contains two
packages (each package with two cores). Using the "--map-by
ppr:2:package" option, we map two processes onto each package and
utilize the "--rank-by" option as show below:

   $ cat myhostfile
   aa
   bb

+-----------------------------------+-----------------------------------+-----------------------------------+
| Command                           | Ranks on "aa"                     | Ranks on "bb"                     |
|===================================|===================================|===================================|
| "--rank-by core"                  | 0 1 ! 2 3                         | 4 5 ! 6 7                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--rank-by package"               | 0 2 ! 1 3                         | 4 6 ! 5 7                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--rank-by package:SPAN"          | 0 4 ! 1 5                         | 2 6 ! 3 7                         |
+-----------------------------------+-----------------------------------+-----------------------------------+

Ranking by slot provides the identical result as ranking by core in
this case — a simple progression of ranks across each node. Ranking by
package does a round-robin ranking across packages within each node
until all processes have been assigned a rank, and then progresses to
the next node.  Adding the ":SPAN" qualifier to the ranking directive
causes the ranking algorithm to treat the entire allocation as a
single entity — thus, the process ranks are assigned across all
packages before circling back around to the beginning.

The binding operation restricts the process to a subset of the CPU
resources on the node.

The processors to be used for binding can be identified in terms of
topological groupings — e.g., binding to an l3cache will bind each
process to all processors within the scope of a single L3 cache within
their assigned location. Thus, if a process is assigned by the mapper
to a certain package, then a "--bind-to l3cache" directive will cause
the process to be bound to the processors that share a single L3 cache
within that package.

To help balance loads, the binding directive uses a round-robin
method, binding a process to the first available specified object type
within the object where the process was mapped. For example, consider
the case where a job is mapped to the package level, and then bound to
core. Each package will have multiple cores, so if multiple processes
are mapped to a given package, the binding algorithm will assign each
process located to a package to a unique core in a round-robin manner.

Binding can only be done to the mapped object or to a resource located
within that object.

An object is considered completely consumed when the number of
processes bound to it equals the number of CPUs within it. Unbound
processes are not considered in this computation. Additional processes
cannot be mapped to consumed objects unless the OVERLOAD qualifier is
provided via the "--bind-to" command line option.

Default process mapping/ranking/binding policies can also be set with
MCA parameters, overridden by the command line options when provided.
MCA parameters can be set on the "prte" command line when starting the
DVM (or in the "prterun" command line for a single-execution job), but
also in a system or user "mca-params.conf" file or as environment
variables, as described in the MCA section below. Some examples
include:

+-----------------------------------+-----------------------------------+-----------------------------------+
| "prun" option                     | MCA parameter key                 | Value                             |
|===================================|===================================|===================================|
| "--map-by core"                   | "rmaps_default_mapping_policy"    | "core"                            |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--map-by package"                | "rmaps_default_mapping_policy"    | "package"                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--rank-by core"                  | "rmaps_default_ranking_policy"    | "core"                            |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--bind-to core"                  | "hwloc_default_binding_policy"    | "core`"                           |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--bind-to package"               | "hwloc_default_binding_policy"    | "package"                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| "--bind-to none"                  | "hwloc_default_binding_policy"    | "none"                            |
+-----------------------------------+-----------------------------------+-----------------------------------+

[placement-limits]


Overloading and Oversubscribing
-------------------------------

This section explores the difference between the terms "overloading"
and "oversubscribing". Users are often confused by the difference
between these two scenarios. As such, this section provides a number
of scenarios to help illustrate the differences.

* "--map-by :OVERSUBSCRIBE" allow more processes on a node than
  allocated

* "--bind-to <object>:overload-allowed" allows for binding more than
  one process in relation to a CPU

The important thing to remember with *oversubscribing* is that it can
be defined separately from the actual number of CPUs on a node. This
allows the mapper to place more or fewer processes per node than CPUs.
By default, PRRTE uses cores to determine slots in the absence of such
information provided in the hostfile or by the resource manager
(except in the case of the "--host" as described in the section on
that command line option.

The important thing to remember with *overloading* is that it is
defined as binding more processes than CPUs. By default, PRRTE uses
cores as a means of counting the number of CPUs. However, the user can
adjust this. For example when using the ":HWTCPUS" qualifier to the "
--map-by" option PRRTE will use hardware threads as a means of
counting the number of CPUs.

For the following examples consider a node with:

* 2 processor packages,

* 10 cores per package, and

* 8 hardware threads per core.

Consider the node from above with the hostfile below:

   $ cat myhostfile
   node01 slots=32
   node02 slots=32

The "slots" token tells PRRTE that it can place up to 32 processes
before *oversubscribing* the node.

If we run the following:

   prun --np 34 --hostfile myhostfile --map-by core --bind-to core hostname

It will return an error at the binding time indicating an
*overloading* scenario.

The mapping mechanism assigns 32 processes to "node01" matching the
"slots" specification in the hostfile. The binding mechanism will bind
the first 20 processes to unique cores leaving it with 12 processes
that it cannot bind without overloading one of the cores (putting more
than one process on the core).

Using the "overload-allowed" qualifier to the "--bind-to core" option
tells PRRTE that it may assign more than one process to a core.

If we run the following:

   prun --np 34 --hostfile myhostfile --map-by core --bind-to core:overload-allowed hostname

This will run correctly placing 32 processes on "node01", and 2
processes on "node02". On "node01" two processes are bound to cores
0-11 accounting for the overloading of those cores.

Alternatively, we could use hardware threads to give binding a lower
level CPU to bind to without overloading.

If we run the following:

   prun --np 34 --hostfile myhostfile --map-by core:HWTCPUS --bind-to hwthread hostname

This will run correctly placing 32 processes on "node01", and 2
processes on "node02". On "node01" two processes are mapped to cores
0-11 but bound to different hardware threads on those cores (the
logical first and second hardware thread). Thus no hardware threads
are overloaded at binding time.

In both of the examples above the node is not oversubscribed at
mapping time because the hostfile set the oversubscription limit to
"slots=32" for each node. It is only after we exceed that limit that
PRRTE will throw an oversubscription error.

Consider next if we ran the following:

   prun --np 66 --hostfile myhostfile --map-by core:HWTCPUS --bind-to hwthread hostname

This will return an error at mapping time indicating an
oversubscription scenario. The mapping mechanism will assign all of
the available slots (64 across 2 nodes) and be left two processes to
map. The only way to map those processes is to exceed the number of
available slots putting the job into an oversubscription scenario.

You can force PRRTE to oversubscribe the nodes by using the
":OVERSUBSCRIBE" qualifier to the "--map-by" option as seen in the
example below:

   prun --np 66 --hostfile myhostfile \
       --map-by core:HWTCPUS:OVERSUBSCRIBE --bind-to hwthread hostname

This will run correctly placing 34 processes on "node01" and 32 on
"node02".  Each process is bound to a unique hardware thread.


Overloading vs. Oversubscription: Package Example
=================================================

Let's extend these examples by considering the package level. Consider
the same node as before, but with the hostfile below:

   $ cat myhostfile
   node01 slots=22
   node02 slots=22

The lowest level CPUs are "cores" and we have 20 total (10 per
package).

If we run:

   prun --np 20 --hostfile myhostfile --map-by package \
       --bind-to package:REPORT hostname

Then 10 processes are mapped to each package, and bound at the package
level.  This is not overloading since we have 10 CPUs (cores)
available in the package at the hardware level.

However, if we run:

   prun --np 21 --hostfile myhostfile --map-by package \
       --bind-to package:REPORT hostname

Then 11 processes are mapped to the first package and 10 to the second
package.  At binding time we have an overloading scenario because
there are only 10 CPUs (cores) available in the package at the
hardware level. So the first package is overloaded.


Overloading vs. Oversubscription: Hardware Threads Example
==========================================================

Similarly, if we consider hardware threads.

Consider the same node as before, but with the hostfile below:

   $ cat myhostfile
   node01 slots=165
   node02 slots=165

The lowest level CPUs are "hwthreads" (because we are going to use the
":HWTCPUS" qualifier) and we have 160 total (80 per package).

If we re-run (from the package example) and add the ":HWTCPUS"
qualifier:

   prun --np 21 --hostfile myhostfile --map-by package:HWTCPUS \
       --bind-to package:REPORT hostname

Without the ":HWTCPUS" qualifier this would be overloading (as we saw
previously). The mapper places 11 processes on the first package and
10 to the second package. The processes are still bound to the package
level. However, with the ":HWTCPUS" qualifier, it is not overloading
since we have 80 CPUs (hwthreads) available in the package at the
hardware level.

Alternatively, if we run:

   prun --np 161 --hostfile myhostfile --map-by package:HWTCPUS \
       --bind-to package:REPORT hostname

Then 81 processes are mapped to the first package and 80 to the second
package.  At binding time we have an overloading scenario because
there are only 80 CPUs (hwthreads) available in the package at the
hardware level.  So the first package is overloaded.
