lamexec - Online in the Cloud

PROGRAM:

NAME

lamexec - Run non-MPI programs on LAM nodes.

SYNOPSIS

lamexec [-fhvD] [-c # | -np #] [-nw | -w] [-pty] [-s node] [-x
VAR1[=VALUE1][,VAR2[=VALUE2],...]] [where] program [-- args]

OPTIONS

-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.

-f Do not configure standard I/O file descriptors - use defaults.

-h Print useful information on this command.

-np # (see below). 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 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.

-nw Do not wait for all processes to complete before exiting lamexec. This option
is mutually exclusive with -w.

-pty Enable pseudo-tty support. Among other things, this enabled line-buffered
output (which is probably what you want). The only reason that this feature is
not enabled by default is because it is so new and has not been extensively
tested yet.

-s node Load the program from this node. This option is not valid on the command line
if an application schema is specified.

-v Be verbose; report on important steps as they are done.

-w Wait for all applications to exit before lamexec exits.

-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 variable names specified with corresponding values. The
parser for the -x option is not very sophisticated; 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.

where A set of node and/or CPU identifiers indicating where to start

-- args Pass these runtime arguments to every new process. This must always be the last
argument to lamexec. This option is not valid on the command line if an
application schema is specified.

DESCRIPTION

lamexec is essentially a clone of the mpirun(1), but is intended for non-MPI programs.

One invocation of lamexec starts a non-MPI application running under LAM. To start the
same program on all LAM nodes, the application can be specified on the lamexec command
line. To start multiple applications on the LAM nodes, 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 lamexec 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
The location nomenclature that is used for the where clause mention in the SYNOPSIS
section, above, is identical to mpirun(1)'s nomenclature. See the mpirun(1) man page for
a lengthy discussion of the location nomenclature.

Note that the by-CPU syntax, while valid for lamexec, is not quite as meaningful because
process rank ordering in MPI_COMM_WORLD is irrelevant. As such, the by-node nomenclature
is typically the preferred syntax for lamexec.

Application Schema or Executable Program?
To distinguish the two different forms, lamexec looks on the command line for nodes 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 nodes and -c both are specified, then copies of the
program are started on the specified nodes 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 nodes, then all LAM nodes are used. If nodes 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 executing 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 LAMAPPLDIR 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 lamexec, standard input is inherited from lamexec. The default is what used to be
the -w option to prevent conflicting 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 lamexec and prints it on the
standard output/error of lamexec. Local processes inherit the standard output/error of
lamexec 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 lamexec.

% lamexec N my_app my_input my_output

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. This allows, among other
things, for line buffered output from remote nodes (which is probably what you want).

This option is not currently the default for lamexec because it has not been thoroughly
tested on a variety of different Unixes. Users are encouraged to use -pty and report any
problems back to the LAM Team.

Current Working Directory
The current working directory for new processes created on the local node is inherited
from lamexec. The current working directory for new processes created on remote nodes is
the remote user's home directory. This default behavior is overridden by the -D option.

The -D option will change the current working directory of new processes to the directory
where the executable resides before the new user's program is invoked.

An alternative to the -D option is the -wd option. -wd allows the user to specify an
arbitrary current working directory (vs. the location of the executable). Note that the
-wd option can be used in application schema files (see appschema(5)) as well.

Process Environment
Processes in the 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 inherited from the user's shell. On the origin node this will
be the shell from which lamboot(1) was invoked and on remote nodes this will be the shell
started by rsh(1). 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
The -x option to lamexec 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 parser 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.

EXAMPLES

lamexec N prog1
Load and execute prog1 on all nodes. Search for the executable file on each node.

lamexec -c 8 prog1
Run 8 copies of prog1 wherever LAM wants to run them.

lamexec 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 lamexec.

lamexec -v myapp
Parse the application schema, myapp, and start all processes specified in it. Report
as each process is created.

lamexec N N -pty -wd /workstuff/output -x DISPLAY run_app.csh
Run the application "run_app.csh" (assumedly a C shell script) twice on each node in
the system (ideal for 2-way SMPs). Also enable pseudo-tty support, change directory
to /workstuff/output, and export the DISPLAY variable to the new processes (perhaps
the shell script will invoke an X application such as xv to display output).

lamexec -np 5 -D `pwd`/my_application
A common usage of lamexec in environments where a filesystem is shared between all
nodes in the multicomputer, using the shell-escaped "pwd" command specifies the full
name of the executable to run. This prevents the need for putting the directory in
the path; the remote notes will have an absolute filename to execute (and change
directory to it upon invocation).

DIAGNOSTICS

lamexec: Exec format error
A non-ASCII character was detected in the application schema. This is usually a
command line usage error where lamexec is expecting an application schema and an
executable file was given.

lamexec: 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

lamexec returns 0 if all processes started by lamexec exit normally. A non-zero value is
returned if an internal error occurred in lamexec, or one or more processes exited
abnormally. If an internal error occurred in lamexec, the corresponding error code is
returned. In the event that one or more processes exit with non-zero exit code, the
return value of the process that lamexec first notices died abnormally will be returned.
Note that, in general, this will be the first process that died but is not guaranteed to
be so.

However, note that if the -nw switch is used, the return value from lamexec does not
indicate the exit status of the processes started by it.

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