Provided by: lam-runtime_7.1.4-3.1_amd64 
NAME
mpirun - Run MPI programs on LAM nodes.
SYNOPSIS
mpirun [-fhvO] [-c # | -np #] [-D | -wd dir] [-ger | -nger] [-sigs | -nsigs] [-ssi key value] [-nw | -w]
[-nx] [-pty | -npty] [-s node] [-t | -toff | -ton] [-tv] [-x VAR1[=VALUE1][,VAR2[=VALUE2],...]] [[-p
prefix_str] [-sa | -sf]] [where] program [-- args]
Note: Although each are individually optional, at least one of where, -np, or -c must be specified in the
above form (i.e., when a schema is not used).
mpirun [-fhvO] [-D | -wd dir] [-ger | -nger] [-sigs | -nsigs] [-ssi key value] [-nw | -w] [-nx] [-pty |
-npty] [-t | -toff | -ton] [-tv] [-x VAR1[=VALUE1][,VAR2[=VALUE2],...]] schema
Note: The -c2c and -lamd options are now obsolete. Use -ssi instead. See the "SSI" section, below.
QUICK SUMMARY
If you're simply looking for how to run an MPI application, you probably want to use the following com‐
mand line:
% mpirun C my_mpi_application
This will run one copy of my_mpi_application on every CPU in the current LAM universe. Alternatively,
"N" can be used in place of "C", indicating that one copy of my_mpi_application should be run on every
node (as opposed to CPU) in the current LAM universe. Finally:
% mpirun -np 4 my_mpi_application
can be used to tell LAM to explicitly run four copies of my_mpi_application, scheduling in a round-robin
fashion by CPU in the LAM universe. See the rest of this page for more details, particularly the "Loca‐
tion Nomenclature" section.
OPTIONS
There are two forms of the mpirun command -- one for programs (i.e., SPMD-style applications), and one
for application schemas (see appschema(5)). Both forms of mpirun use the following options by default:
-nger -w. These may each be overriden by their counterpart options, described below.
Additionally, mpirun will send the name of the directory where it was invoked on the local node to each
of the remote nodes, and attempt to change to that directory. See the "Current Working Directory" sec‐
tion, below.
-c # Synonym for -np (see below).
-D Use the executable program location as the current working directory for created processes.
The current working directory of the created processes will be set before the user's program is
invoked. This option is mutually exclusive with -wd.
-f Do not configure standard I/O file descriptors - use defaults.
-h Print useful information on this command.
-ger Enable GER (Guaranteed Envelope Resources) communication protocol and error reporting. See
MPI(7) for a description of GER. This option is mutually exclusive with -nger.
-nger Disable GER (Guaranteed Envelope Resources). This option is mutually exclusive with -ger.
-nsigs Do not have LAM catch signals in the user application. This is the default, and is mutually
exclusive with -sigs.
-np # Run this many copies of the program on the given nodes. This option indicates that the speci‐
fied file is an executable program and not an application schema. If no nodes are specified,
all LAM nodes are considered for scheduling; LAM will schedule the programs in a round-robin
fashion, "wrapping around" (and scheduling multiple copies on a single node) if necessary.
-npty Disable pseudo-tty support. Unless you are having problems with pseudo-tty support, you proba‐
bly do not need this option. Mutually exlclusive with -pty.
-nw Do not wait for all processes to complete before exiting mpirun. This option is mutually ex‐
clusive with -w.
-nx Do not automatically export LAM_MPI_*, LAM_IMPI_*, or IMPI_* environment variables to the re‐
mote nodes.
-O Multicomputer is homogeneous. Do no data conversion when passing messages. THIS FLAG IS NOW
OBSOLETE.
-pty Enable pseudo-tty support. Among other things, this enabled line-buffered output (which is
probably what you want). This is the default. Mutually exclusive with -npty.
-s node Load the program from this node. This option is not valid on the command line if an applica‐
tion schema is specified.
-sigs Have LAM catch signals in the user process. This options is mutually exclusive with -nsigs.
-ssi key value
Send arguments to various SSI modules. See the "SSI" section, below.
-t, -ton Enable execution trace generation for all processes. Trace generation will proceed with no
further action. These options are mutually exclusive with -toff.
-toff Enable execution trace generation for all processes. Trace generation for message passing
traffic will begin after processes collectively call MPIL_Trace_on(2). Note that trace genera‐
tion for datatypes and communicators will proceed regardless of whether trace generation is en‐
abled for messages or not. This option is mutually exclusive with -t and -ton.
-tv Launch processes under the TotalView Debugger.
-v Be verbose; report on important steps as they are done.
-w Wait for all applications to exit before mpirun exits.
-wd dir Change to the directory dir before the user's program executes. Note that if the -wd option
appears both on the command line and in an application schema, the schema will take precendence
over the command line. This option is mutually exclusive with -D.
-x Export the specified environment variables to the remote nodes before executing the program.
Existing environment variables can be specified (see the Examples section, below), or new vari‐
able names specified with corresponding values. The parser for the -x option is not very so‐
phisticated; it does not even understand quoted values. Users are advised to set variables in
the environment, and then use -x to export (not define) them.
-sa Display the exit status of all MPI processes irrespecive of whether they fail or run success‐
fully.
-sf Display the exit status of all processes only if one of them fails.
-p prefix_str
Prefixes each process status line displayed by [-sa] and [-sf] by the prefix_str.
where A set of node and/or CPU identifiers indicating where to start program. See bhost(5) for a de‐
scription of the node and CPU identifiers. mpirun will schedule adjoining ranks in
MPI_COMM_WORLD on the same node when CPU identifiers are used. For example, if LAM was booted
with a CPU count of 4 on n0 and a CPU count of 2 on n1 and where is C, ranks 0 through 3 will
be placed on n0, and ranks 4 and 5 will be placed on n1.
args Pass these runtime arguments to every new process. These must always be the last arguments to
mpirun. This option is not valid on the command line if an application schema is specified.
DESCRIPTION
One invocation of mpirun starts an MPI application running under LAM. If the application is simply SPMD,
the application can be specified on the mpirun command line. If the application is MIMD, comprising mul‐
tiple programs, an application schema is required in a separate file. See appschema(5) for a description
of the application schema syntax, but it essentially contains multiple mpirun command lines, less the
command name itself. The ability to specify different options for different instantiations of a program
is another reason to use an application schema.
Location Nomenclature
As described above, mpirun can specify arbitrary locations in the current LAM universe. Locations can be
specified either by CPU or by node (noted by the "where" in the SYNTAX section, above). Note that LAM
does not bind processes to CPUs -- specifying a location "by CPU" is really a convenience mechanism for
SMPs that ultimately maps down to a specific node.
Note that LAM effectively numbers MPI_COMM_WORLD ranks from left-to-right in the where, regardless of
which nomenclature is used. This can be important because typical MPI programs tend to communicate more
with their immediate neighbors (i.e., myrank +/- X) than distant neighbors. When neighbors end up on the
same node, the shmem RPIs can be used for communication rather than the network RPIs, which can result in
faster MPI performance.
Specifying locations by node will launch one copy of an executable per specified node. Using a capitol
"N" tells LAM to use all available nodes that were lambooted (see lamboot(1)). Ranges of specific nodes
can also be specified in the form "nR[,R]*", where R specifies either a single node number or a valid
range of node numbers in the range of [0, num_nodes). For example:
mpirun N a.out
Runs one copy of the the executable a.out on all available nodes in the LAM universe. MPI_COMM_WORLD
rank 0 will be on n0, rank 1 will be on n1, etc.
mpirun n0-3 a.out
Runs one copy of the the executable a.out on nodes 0 through 3. MPI_COMM_WORLD rank 0 will be on n0,
rank 1 will be on n1, etc.
mpirun n0-3,8-11,15 a.out
Runs one copy of the the executable a.out on nodes 0 through 3, 8 through 11, and 15. MPI_COMM_WORLD
ranks will be ordered as follows: (0, n0), (1, n1), (2, n2), (3, n3), (4, n8), (5, n9), (6, n10), (7,
n11), (8, n15).
Specifying by CPU is the preferred method of launching MPI jobs. The intent is that the boot schema used
with lamboot(1) will indicate how many CPUs are available on each node, and then a single, simple mpirun
command can be used to launch across all of them. As noted above, specifying CPUs does not actually bind
processes to CPUs -- it is only a convenience mechanism for launching on SMPs. Otherwise, the by-CPU no‐
tation is the same as the by-node notation, except that "C" and "c" are used instead of "N" and "n".
Assume in the following example that the LAM universe consists of four 4-way SMPs. So c0-3 are on n0,
c4-7 are on n1, c8-11 are on n2, and 13-15 are on n3.
mpirun C a.out
Runs one copy of the the executable a.out on all available CPUs in the LAM universe. This is typi‐
cally the simplest (and preferred) method of launching all MPI jobs (even if it resolves to one
process per node). MPI_COMM_WORLD ranks 0-3 will be on n0, ranks 4-7 will be on n1, ranks 8-11 will
be on n2, and ranks 13-15 will be on n3.
mpirun c0-3 a.out
Runs one copy of the the executable a.out on CPUs 0 through 3. All four ranks of MPI_COMM_WORLD will
be on MPI_COMM_WORLD.
mpirun c0-3,8-11,15 a.out
Runs one copy of the the executable a.out on CPUs 0 through 3, 8 through 11, and 15. MPI_COMM_WORLD
ranks 0-3 will be on n0, 4-7 will be on n2, and 8 will be on n3.
The reason that the by-CPU nomenclature is preferred over the by-node nomenclature is best shown through
example. Consider trying to run the first CPU example (with the same MPI_COMM_WORLD mapping) with the
by-node nomenclature -- run one copy of a.out for every available CPU, and maximize the number of local
neighbors to potentially maximize MPI performance. One solution would be to use the following command:
mpirun n0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3 a.out
This works, but is definitely klunky to type. It is typically easier to use the by-CPU notation. One
might think that the following is equivalent:
mpirun N -np 16 a.out
This is not equivalent because the MPI_COMM_WORLD rank mappings will be assigned by node rather than by
CPU. Hence rank 0 will be on n0, rank 1 will be on n1, etc. Note that the following, however, is equiv‐
alent, because LAM interprets lack of a where as "C":
mpirun -np 16 a.out
However, a "C" can tend to be more convenient, especially for batch-queuing scripts because the exact
number of processes may vary between queue submissions. Since the batch system will determine the final
number of CPUs available, having a generic script that effectively says "run on everything you gave me"
may lead to more portable / re-usable scripts.
Finally, it should be noted that specifying multiple where clauses are perfectly acceptable. As such,
mixing of the by-node and by-CPU syntax is also valid, albiet typically not useful. For example:
mpirun C N a.out
However, in some cases, specifying multiple where clauses can be useful. Consider a parallel application
where MPI_COMM_WORLD rank 0 will be a "manager" and therefore consume very few CPU cycles because it is
usually waiting for "worker" processes to return results. Hence, it is probably desirable to run one
"worker" process on all available CPUs, and run one extra process that will be the "manager":
mpirun c0 C manager-worker-program
Application Schema or Executable Program?
To distinguish the two different forms, mpirun looks on the command line for where or the -c option. If
neither is specified, then the file named on the command line is assumed to be an application schema. If
either one or both are specified, then the file is assumed to be an executable program. If where and -c
both are specified, then copies of the program are started on the specified nodes/CPUs according to an
internal LAM scheduling policy. Specifying just one node effectively forces LAM to run all copies of the
program in one place. If -c is given, but not where, then all available CPUs on all LAM nodes are used.
If where is given, but not -c, then one copy of the program is run on each node.
Program Transfer
By default, LAM searches for executable programs on the target node where a particular instantiation will
run. If the file system is not shared, the target nodes are homogeneous, and the program is frequently
recompiled, it can be convenient to have LAM transfer the program from a source node (usually the local
node) to each target node. The -s option specifies this behavior and identifies the single source node.
Locating Files
LAM looks for an executable program by searching the directories in the user's PATH environment variable
as defined on the source node(s). This behavior is consistent with logging into the source node and exe‐
cuting the program from the shell. On remote nodes, the "." path is the home directory.
LAM looks for an application schema in three directories: the local directory, the value of the LAMAP‐
PLDIR environment variable, and laminstalldir/boot, where "laminstalldir" is the directory where LAM/MPI
was installed.
Standard I/O
LAM directs UNIX standard input to /dev/null on all remote nodes. On the local node that invoked mpirun,
standard input is inherited from mpirun. The default is what used to be the -w option to prevent con‐
flicting access to the terminal.
LAM directs UNIX standard output and error to the LAM daemon on all remote nodes. LAM ships all captured
output/error to the node that invoked mpirun and prints it on the standard output/error of mpirun. Local
processes inherit the standard output/error of mpirun and transfer to it directly.
Thus it is possible to redirect standard I/O for LAM applications by using the typical shell redirection
procedure on mpirun.
% mpirun C my_app my_input my_output
Note that in this example only the local node (i.e., the node where mpirun was invoked from) will receive
the stream from my_input on stdin. The stdin on all the other nodes will be tied to /dev/null. However,
the stdout from all nodes will be collected into the my_output file.
The -f option avoids all the setup required to support standard I/O described above. Remote processes
are completely directed to /dev/null and local processes inherit file descriptors from lamboot(1).
Pseudo-tty support
The -pty option enabled pseudo-tty support for process output (it is also enabled by default). This al‐
lows, among other things, for line buffered output from remote nodes (which is probably what you want).
This option can be disabled with the -npty switch.
Process Termination / Signal Handling
During the run of an MPI application, if any rank dies abnormally (either exiting before invoking MPI_FI‐
NALIZE, or dying as the result of a signal), mpirun will print out an error message and kill the rest of
the MPI application.
By default, LAM/MPI only installs a signal handler for one signal in user programs (SIGUSR2 by default,
but this can be overridden when LAM is configured and built). Therefore, it is safe for users to install
their own signal handlers in LAM/MPI programs (LAM notices death-by-signal cases by examining the
process' return status provided by the operating system).
User signal handlers should probably avoid trying to cleanup MPI state -- LAM is neither thread-safe nor
async-signal-safe. For example, if a seg fault occurs in MPI_SEND (perhaps because a bad buffer was
passed in) and a user signal handler is invoked, if this user handler attempts to invoke MPI_FINALIZE,
Bad Things could happen since LAM/MPI was already "in" MPI when the error occurred. Since mpirun will
notice that the process died due to a signal, it is probably not necessary (and safest) for the user to
only clean up non-MPI state.
If the -sigs option is used with mpirun, LAM/MPI will install several signal handlers to locally on each
rank to catch signals, print out error messages, and kill the rest of the MPI application. This is some‐
what redundant behavior since this is now all handled by mpirun, but it has been left for backwards com‐
patability.
Process Exit Statuses
The -sa, -sf, and -p parameters can be used to display the exist statuses of the individual MPI
processes as they terminate. -sa forces the exit statuses to be displayed for all processes; -sf only
displays the exist statuses if at least one process terminates either by a signal or a non-zero exit sta‐
tus (note that exiting before invoking MPI_FINALIZE will cause a non-zero exit status).
The status of each process is printed out, one per line, in the following format:
prefix_string node pid killed status
If killed is 1, then status is the signal number. If killed is 0, then status is the exit status of the
process.
The default prefix_string is "mpirun:", but the -p option can be used override this string.
Current Working Directory
The default behavior of mpirun has changed with respect to the directory that processes will be started
in.
The -wd option to mpirun allows the user to change to an arbitrary directory before their program is in‐
voked. It can also be used in application schema files to specify working directories on specific nodes
and/or for specific applications.
If the -wd option appears both in a schema file and on the command line, the schema file directory will
override the command line value.
The -D option will change the current working directory to the directory where the executable resides.
It cannot be used in application schema files. -wd is mutually exclusive with -D.
If neither -wd nor -D are specified, the local node will send the directory name where mpirun was invoked
from to each of the remote nodes. The remote nodes will then try to change to that directory. If they
fail (e.g., if the directory does not exists on that node), they will start with from the user's home di‐
rectory.
All directory changing occurs before the user's program is invoked; it does not wait until MPI_INIT is
called.
Process Environment
Processes in the MPI application inherit their environment from the LAM daemon upon the node on which
they are running. The environment of a LAM daemon is fixed upon booting of the LAM with lamboot(1) and
is typically inherited from the user's shell. On the origin node, this will be the shell from which lam‐
boot(1) was invoked; on remote nodes, the exact environment is determined by the boot SSI module used by
lamboot(1). The rsh boot module, for example, uses either rsh/ssh to launch the LAM daemon on remote
nodes, and typically executes one or more of the user's shell-setup files before launching the LAM dae‐
mon. When running dynamically linked applications which require the LD_LIBRARY_PATH environment variable
to be set, care must be taken to ensure that it is correctly set when booting the LAM.
Exported Environment Variables
All environment variables that are named in the form LAM_MPI_*, LAM_IMPI_*, or IMPI_* will automatically
be exported to new processes on the local and remote nodes. This exporting may be inhibited with the -nx
option.
Additionally, the -x option to mpirun can be used to export specific environment variables to the new
processes. While the syntax of the -x option allows the definition of new variables, note that the pars‐
er for this option is currently not very sophisticated - it does not even understand quoted values.
Users are advised to set variables in the environment and use -x to export them; not to define them.
Trace Generation
Two switches control trace generation from processes running under LAM and both must be in the on posi‐
tion for traces to actually be generated. The first switch is controlled by mpirun and the second switch
is initially set by mpirun but can be toggled at runtime with MPIL_Trace_on(2) and MPIL_Trace_off(2).
The -t (-ton is equivalent) and -toff options all turn on the first switch. Otherwise the first switch
is off and calls to MPIL_Trace_on(2) in the application program are ineffective. The -t option also
turns on the second switch. The -toff option turns off the second switch. See MPIL_Trace_on(2) and lam‐
trace(1) for more details.
MPI Data Conversion
LAM's MPI library converts MPI messages from local representation to LAM representation upon sending them
and then back to local representation upon receiving them. If the case of a LAM consisting of a homoge‐
neous network of machines where the local representation differs from the LAM representation this can re‐
sult in unnecessary conversions.
The -O switch used to be necessary to indicate to LAM whether the mulitcomputer was homogeneous or not.
LAM now automatically determines whether a given MPI job is homogeneous or not. The -O flag will silent‐
ly be accepted for backwards compatability, but it is ignored.
SSI (System Services Interface)
The -ssi switch allows the passing of parameters to various SSI modules. LAM's SSI modules are described
in detail in lamssi(7). SSI modules have direct impact on MPI programs because they allow tunable para‐
meters to be set at run time (such as which RPI communication device driver to use, what parameters to
pass to that RPI, etc.).
The -ssi switch takes two arguments: key and value. The key argument generally specifies which SSI mod‐
ule will receive the value. For example, the key "rpi" is used to select which RPI to be used for trans‐
porting MPI messages. The value argument is the value that is passed. For example:
mpirun -ssi rpi lamd N foo
Tells LAM to use the "lamd" RPI and to run a single copy of "foo" on every node.
mpirun -ssi rpi tcp N foo
Tells LAM to use the "tcp" RPI.
mpirun -ssi rpi sysv N foo
Tells LAM to use the "sysv" RPI.
And so on. LAM's RPI SSI modules are described in lamssi_rpi(7).
The -ssi switch can be used multiple times to specify different key and/or value arguments. If the same
key is specified more than once, the values are concatenated with a comma (",") separating them.
Note that the -ssi switch is simply a shortcut for setting environment variables. The same effect may be
accomplished by setting corresponding environment variables before running mpirun. The form of the envi‐
ronment variables that LAM sets are: LAM_MPI_SSI_key=value.
Note that the -ssi switch overrides any previously set environment variables. Also note that unknown key
arguments are still set as environment variable -- they are not checked (by mpirun) for correctness. Il‐
legal or incorrect value arguments may or may not be reported -- it depends on the specific SSI module.
The -ssi switch obsoletes the old -c2c and -lamd switches. These switches used to be relevant because
LAM could only have two RPI's available at a time: the lamd RPI and one of the C2C RPIs. This is no
longer true -- all RPI's are now available and choosable at run-time. Selecting the lamd RPI is shown in
the examples above. The -c2c switch has no direct translation since "C2C" used to refer to all other
RPI's that were not the lamd RPI. As such, -ssi rpi value must be used to select the specific desired
RPI (whether it is "lamd" or one of the other RPI's).
Guaranteed Envelope Resources
By default, LAM will guarantee a minimum amount of message envelope buffering to each MPI process pair
and will impede or report an error to a process that attempts to overflow this system resource. This ro‐
bustness and debugging feature is implemented in a machine specific manner when direct communication is
used. For normal LAM communication via the LAM daemon, a protocol is used. The -nger option disables
GER and the measures taken to support it. The minimum GER is configured by the system administrator when
LAM is installed. See MPI(7) for more details.
EXAMPLES
Be sure to also see the examples in the "Location Nomenclature" section, above.
mpirun N prog1
Load and execute prog1 on all nodes. Search the user's $PATH for the executable file on each node.
mpirun -c 8 prog1
Run 8 copies of prog1 wherever LAM wants to run them.
mpirun n8-10 -v -nw -s n3 prog1 -q
Load and execute prog1 on nodes 8, 9, and 10. Search for prog1 on node 3 and transfer it to the
three target nodes. Report as each process is created. Give "-q" as a command line to each new
process. Do not wait for the processes to complete before exiting mpirun.
mpirun -v myapp
Parse the application schema, myapp, and start all processes specified in it. Report as each process
is created.
mpirun -npty -wd /work/output -x DISPLAY C my_application
Start one copy of "my_application" on each available CPU. The number of available CPUs on each node
was previously specified when LAM was booted with lamboot(1). As noted above, mpirun will schedule
adjoining rank in MPI_COMM_WORLD on the same node where possible. For example, if n0 has a CPU count
of 8, and n1 has a CPU count of 4, mpirun will place MPI_COMM_WORLD ranks 0 through 7 on n0, and 8
through 11 on n1. This tends to maximize on-node communication for many parallel applications; when
used in conjunction with the multi-protocol network/shared memory RPIs in LAM (see the RELEASE_NOTES
and INSTALL files with the LAM distribution), overall communication performance can be quite good.
Also disable pseudo-tty support, change directory to /work/output, and export the DISPLAY variable to
the new processes (perhaps my_application will invoke an X application such as xv to display output).
DIAGNOSTICS
mpirun: Exec format error
This usually means that either a number of processes or an appropriate where clause was not speci‐
fied, indicating that LAM does not know how many processes to run. See the EXAMPLES and "Location
Nomenclature" sections, above, for examples on how to specify how many processes to run, and/or where
to run them. However, it can also mean that a non-ASCII character was detected in the application
schema. This is usually a command line usage error where mpirun is expecting an application schema
and an executable file was given.
mpirun: syntax error in application schema, line XXX
The application schema cannot be parsed because of a usage or syntax error on the given line in the
file.
filename: No such file or directory
This error can occur in two cases. Either the named file cannot be located or it has been found but
the user does not have sufficient permissions to execute the program or read the application schema.
RETURN VALUE
mpirun returns 0 if all ranks started by mpirun exit after calling MPI_FINALIZE. A non-zero value is re‐
turned if an internal error occurred in mpirun, or one or more ranks exited before calling MPI_FINALIZE.
If an internal error occurred in mpirun, the corresponding error code is returned. In the event that one
or more ranks exit before calling MPI_FINALIZE, the return value of the rank of the process that mpirun
first notices died before calling MPI_FINALIZE will be returned. Note that, in general, this will be the
first rank that died but is not guaranteed to be so.
However, note that if the -nw switch is used, the return value from mpirun does not indicate the exit
status of the ranks.
SEE ALSO
bhost(5), lamexec(1), lamssi(7), lamssi_rpi(7), lamtrace(1), loadgo(1), MPIL_Trace_on(2), mpimsg(1), mpi‐
task(1)
LAM 7.1.4 July, 2007 MPIRUN(1)