srun.1

\." $Id$
.\"
.TH SRUN "1" "November 2002" "srun 0.1" "slurm components"
.SH "NAME"
srun \- run parallel jobs
.SH SYNOPSIS
.B srun
[\fIOPTIONS\fR...] \fIexecutable \fR[\fIargs\fR...]
.br
.B srun
\-\-allocate [\fIOPTIONS\fR...] [job_script]
.br
.B srun
\-\-attach=jobid
.SH DESCRIPTION
Allocate resources and optionally initiate parallel jobs on
clusters managed by SLURM.
.TP
parallel run options
.TP
\fB\-n\fR, \fB\-\-nprocs\fR=\fInprocs\fR
Specify the number of processes to run. Request that
.B srun
allocate \fInprocs\fR processes. Specification of the number of processes
per node may be achieved with the
.B -c
and
.B -N
options. If unspecified, the default is one process.
.TP
\fB\-c\fR, \fB\-\-cpus\-per\-task\fR=\fIncpus\fR
Request that \fIncpus\fR be allocated \fBper process\fR. This may be
useful if the job will be multithreaded and requires more than one cpu
per task for optimal performance. The default is one cpu per process.
.TP
\fB\-N\fR, \fB\-\-nodes\fR=\fInnodes\fR
Request that \fInnodes\fR nodes be allocated to this job. The default
is to allocate one cpu per process, such that nodes with one cpu will
run one process, nodes with 2 cpus will be allocated 2 processes, etc.
The distribution of processes across nodes may be controlled using this
option along with the
.B -n
and
.B -c
options.
.TP
\fB\-p\fR, \fB\-\-partition\fR=\fIpartition\fR
Request resources from partition "\fIpartition\fR." Partitions
are created by the slurm administrator.
.TP
\fB\-t\fR, \fB\-\-time\fR=\fIminutes\fR
Establish a time limit to terminate the job after the specified number of minutes.
.TP
\fB\-\-cddir\fR=\fIpath\fR
have the remote processes do a chdir to \fIpath\fR before beginning
execution. The default is to chdir to the current working directory
of the \fBsrun\fR process.
.TP
\fB\-I\fR, \fB\-\-immediate\fR
exit if resources are not immediately
available. By default, \fB\-\-immediate\fR is off, and
.B srun
will block until resources become available.
.TP
\fB\-k\fR, \fB\-\-kill-off\fR
Do not automatically terminate a job of one of the nodes it has been allocated 
fails. The job will assume all responsibilities for fault-tolerance. The default 
action is to termniate the job upon node failure.
.TP
\fB\-s\fR, \fB\-\-share\fR
The job can share nodes with other running jobs. This may result in faster job 
initiation and higher system utilization, but lower application performance.
.TP
\fB\-O\fR, \fB\-\-overcommit\fR
overcommit resources. Normally,
.B srun
will not allocate more than one process to a cpu. By specifying
\fB\-\-overcommit\fR you are explicitly allowing more than one process
per cpu.
.TP
\fB\-T\fR, \fB\-\-threads\fR=\fInthreads\fR
Request that 
.B srun
use \fInthreads\fR to initiate and control the parallel job. The 
default value is the smaller of 10 or the number of nodes allocated.
.TP
\fB\-l\fR, \fB\-\-label\fR
prepend task number to lines of stdout/err. Normally, stdout and stderr
from remote tasks is line-buffered directly to the stdout and stderr of
.B srun
. The \fB\-\-label\fR option will prepend lines of output with the remote
task id.
.TP
\fB\-m\fR, \fB\-\-distribution\fR=(\fIblock\fR|\fIcyclic\fR)
Specify an alternate distribution method for remote processes.
.RS
.TP
.B block
The block method of distribution will allocate processes in-order to
the cpus on a node. This is the default behavior.
.TP
.B cyclic
The cyclic method distributes processes in a round-robin fashion across
the allocated nodes. That is, process 1 will be allocated to the first
node, process 2 to the second, and so on.
.RE
.TP
\fB\-J\fR, \fB\-\-job\-name\fR=\fIjobname\fR
Specify a name for the job. The specified name will appear along with
the job id number when querying running jobs on the system. The default
is the supplied \fBexecutable\fR program's name.
.TP
\fB\-o\fR, \fB\-\-output\fR=\fIout\fR
Specify how stdout is to be directed. By default,
.B srun
collects stdout from all tasks and line buffers this output to
the attached terminal. With \fB\-\-output\fR stdout may be redirected
to a file, to one file per task, or to /dev/null. See \fBIO Redirection\fR
below.
.TP
\fB\-i\fR, \fB\-\-input\fR=\fIin\fR
Specify how stdin is to redirected. By default,
.B srun
redirects stdin to all tasks from /dev/null. See \fBIO Redirection\fR
below for more options.
.TP
\fB\-e\fR, \fB\-\-error\fR=\fIerr\fR
Specify how stderr is to be redirected. By default,
.B srun
redirects stderr to the same file as stdout, if one is specified. The
\fB\-\-error\fR option is provided to allow stdout and stderr to be
redirected to different locations.
See \fBIO Redirection\fR below for more options.
.TP
\fB\-b\fR, \fB\-\-batch\fR
Submit in "batch mode." \fBsrun\fR will make a copy of the \fIexecutable\fR 
file (a script) and submit the request for execution when resouces are 
available. \fBsrun\fR will terminate after the request has been submitted. 
The \fIexecutable\fR file will run on the first node allocated to the 
job and must contain \fBsrun\fR commands to initiate parallel tasks.
stdin will be redirected from /dev/null, stdout and stderr will be
redirected to a file (default is \fIjobname\fR.out or \fIjobid\fR.out in
current working directory, see \fB\-o\fR for other IO options). 
\fIexecutable\fR must be specified using either a fully qualified 
pathname or its pathname will be relative to the current working directory. 
The search path will not be used to locate the file. \fIexecutable\fR 
will be interpretted by the user's default shell unless the file begins 
with "#!" followed by the fully qualified pathname of a valid shell.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
verbose operation. Multiple \fB-v\fR's will further increase the verbosity of
.B srun.
.TP
\fB\-W\fR, \fB\-\-wait\fR=\fIseconds\fR
Specify how long to wait after the first task terminates before terminating 
all remaining tasks. The default value is unlimited. This can be useful to 
insure that a a job is terminated in a timely fashion in the event that one 
or more tasks terminate prematurely.
.TP
\fB\-d\fR, \fB\-\-debug\fR
enable debug output. Multiple \fB-d\fR's increase the debug level of
.B srun
.PP
Allocate options:
.TP
\fB\-A\fR, \fB\-\-allocate\fR
allocate resources and spawn a shell. When \fB\-\-allocate\fR is specified to
.B srun
, no remote tasks are started. Instead a subshell is started that has access
to the allocated resources. Multiple jobs can then be run on the same cpus
from within this subshell. See \fBAllocate Mode\fR below.
.PP
Attach to running job:
.TP
\fB\-a\fR, \fB\-\-attach\fR=\fIid\fR
This option will attach
.B srun
to a running job with job id = \fIid\fR. Provided that the calling user
has access to that running job, stdout and stderr will be redirected to the
current session and signals received by
.B srun
will be forwarded to the remote processes.
.TP
\fB\-j\fR, \fB\-\-join\fR
Join with running job. This will duplicate stdout/stderr to the calling
\fBsrun\fR. stdin and signals will not be propagated to the job.
\fB\-\-join\fR is only allowed with \fB\-\-attach\fR.
.TP
\fB\-s\fR, \fB\-\-steal\fR
Steal the connection to the running job. This will close any open
sessions with the specified job and allow stdin and signals to be propagated.
\fB\-\-steal\fR is only allowed with \fB\-\-attach\fR.
.PP
Constraint Options. The following options all put constraints on the nodes
that may be considered for the job:
.TP
\fB\-\-mincpus\fR=\fIn\fR
Specify minimum number of cpus per node
.TP
\fB\-\-mem\fR=\fIMB\fR
Specify a minimum amount of real memory
.TP
\fB\-\-vmem\fR=\fIMB\fR
Specify a minimum amount of virtual memory
.TP
\fB\-\-tmp\fR=\fIMB\fR
Specify a minimum amount of temporary disk space
.TP
\fB\-C\fR, \fB\-\-constraint\fR=\fIlist\fR
specify a list of constraints. The \fIlist\fR of constraints is
a comma separated list of features that have been assigned to the
nodes by the slurm administrator. If no nodes have the requested
feature, then the job will be rejected by the slurm job manager.
.TP
\fB\-\-contiguous\fR
demand a contiguous range of nodes. The default is on. Specify
--contiguous=no if a contiguous range of nodes is not a constraint.
.TP
\fB\-w\fR, \fB\-\-nodelist\fR=\fIhost1,host2,...\fR or \fIfilename\fR
request a specific list of hosts. The job will contain \fIat least\fR
these hosts. The list may be specified as a comma-separated list of
hosts, a range of hosts (host[1-5,7,...] for example), or a filename.
The host list will be assumed to be a filename if it contains a "/"
character.
.PP
Help options
.TP
-?, \fB\-\-help\fR
Show this help message
.TP
\fB\-\-usage\fR
Display brief usage message
.PP
Other options
.TP
\fB\-V\fR, \fB\-\-version\fR
output version information and exit
.PP
Unless the \fB\-a\fR (\fB\-\-attach\fR) or \fB-A\fR (\fB\-\-allocate\fR)
options are specified (see \fBAllocate mode\fR and \fBAttaching to jobs\fR
below),
.B srun
will submit the job request to the slurm job controller, then initiate all
processes on the remote nodes. If the request cannot be met immediately,
.B srun
will block until the resources are free to run the job. If the
\fB\-I\fR (\fB\-\-immediate\fR) option is specified
.B srun
will terminate if resources are not immediately available.
.PP
When initiating remote processes
.B srun
will propagate the current working directory, unless
\fB\-\-cddir\fR=\fIpath\fR is specified, in which case \fIpath\fR will
become the working directory for the remote processes.
.PP
The \fB-n\fB, \fB-c\fR, and \fB-N\fR options control how CPUs  and
nodes will be allocated to the job. When specifying only the number
of processes to run with \fB-n\fR, a default of one CPU per process
is allocated. By specifying the number of CPUs required per task (\fB-c\fR),
more than one CPU may be allocated per process. If the number of nodes
is specified with \fB-N\fR,
.B srun
will attempt to allocate \fIat least\fR the number of nodes specified.
.PP
Combinations of the above three options may be used to change how
processes are distributed across nodes and cpus. For instance, by specifying
both the number of processes and number of nodes on which to run, the
number of processes per node is implied. However, if the number of CPUs
per process is more important then number of processes (\fB-n\fR) and the
number of CPUs per process (\fB-c\fR) should be specified.
.PP
.B srun
will refuse to  allocate more than one process per CPU unless
\fB\-\-overcommit\fR (\fB\-O\fR) is also specified.
.PP
.B srun
will attempt to meet the above specifications "at a minimum." That is,
if 16 nodes are requested for 32 processes, and some nodes do not have
2 CPUs, the allocation of nodes will be increased in order to meet the
demand for CPUs. In other words, a \fIminimum\fR of 16 nodes are being
requested. However, if 16 nodes are requested for 15 processes,
.B srun
will consider this an error, as 15 processes cannot run across 16 nodes.
.PP
.B "IO Redirection"
.PP
By default stdout and stderr will be redirected from all tasks to the
stdout and stderr of
.B srun
, and stdin will be redirected from /dev/null to all tasks. This
behavior may be changed with the \fB\-\-output\fR, \fB\-\-error\fR,
and \fB\-\-input\fR (\fB\-o\fR, \fB\-e\fR, \fB\-i\fR) options. Valid
arguments to these options are
.TP 10
all
stdout stderr is redirected from all tasks to srun (This is the default).
stdin is forwarded to all tasks.
.TP
none
stdout and stderr are redirected to /dev/null.
stdin is redirected from /dev/null (This is the default for stdin)
.TP
filename
stdout and stderr are redirected to the named file (relative to the
current working directory of the job). stdin is redirected from the
named file.
.TP
format string
If a format string is provided (such as "output.%d"),
.B srun
will open one file per task passing the task id as the argument to
the format string. The format specifier may be any valid printf
format, as long as it takes a numeric argument.
.PP
.PP
.B "Allocate Mode"
.PP
When the allocate option is specified (\fB\-A\fR, \fB\-\-allocate\fR)
\fBsrun\fR will not initiate any remote processes after acquiring
resources. Instead, \fBsrun\fR will spawn a subshell which has access
to the acquired resources. Subsequent instances of \fBsrun\fR from within
this subshell will then run on these resources.
.PP
If the name of a script is specified on the
commandline with \fB\-\-allocate\fR, the spawned shell will run the
specified script. Resources allocated in this way will only be freed
when the subshell terminates.
.PP
.B "Attaching to a running job"
.PP
Use of the \fB-a\fR \fIjobid\fR (or \fB\-\-attach\fR) option allows
\fBsrun\fR to reattach to a running job, receiving stdout and stderr
from the job and forwarding signals to the job, just as if the current
session of \fBsrun\fR had started the job. (stdin, however, cannot
be forwarded to the job).
.PP
There are two ways to reattach to a running job. The default method
is to steal any current connections to the job. In this case, the
\fBsrun\fR process currently managing the job will be terminated, and
control will be relegated to the caller. To allow the current
\fBsrun\fR to continue managing the running job, the \fB\-j\fB
(\fB\-\-join\fR) option may be specified. When joining with the
running job, stdout and stderr are duplicated to the new \fBsrun\fR
session, but signals are not forwarded to the remote job.
.PP
Node and CPU selection options do not make sense when specifying 
\fB\-\-attach\fR, and it is an error to use \fB-n\fR, \fB-c\fR, 
or \fB-N\fR in attach mode.
.PP
.SH "ENVIRONMENT VARIABLES"
.PP
Some
.B srun
options may be set via environment variables. These environment
variables, along with their corresponding options, are listed below.
(Note: commandline options will always override these settings)
.TP 20
SLURM_NPROCS
\fB\-n, \-\-nprocs\fR=\fIn\fR
.TP
SLURM_CPUS_PER_TASK
\fB\-c, \-\-ncpus\-per\-task\fR=\fIn\fR
.TP
SLURM_NNODES
\fB\-N, \-\-nodes\fR=\fIn\fR
.TP
SLURM_PARTITION
\fB\-p, --partition\fR=\fIpartition\fR
.TP
SLURM_STDOUTMODE
\fB\-o, \-\-output\fR=\fImode\fR
.TP
SLURM_STDINMODE
\fB\-i, \-\-input\fR=\fImode\fR
.TP
SLURM_STDERRMODE
\fB\-e, \-\-error\fR=\fImode\fR
.TP
SLURM_DISTRIBUTION
\fB\-m, \-\-distribution\fR=(\fIblock|cyclic\fR)
.TP
SLURM_DEBUG
\fB\-d, \-\-debug\fR
.PP
Additionally,
.B srun
will set some environment variables  in the environment of the
executing tasks on the remote compute nodes. These environment variables
are:
.TP 20
SLURM_JOBID
job id of the executing job.
.TP
SLURM_RANK
the MPI rank of the current process
.TP
SLURM_NPROCS
total number of processes in the current job
.TP
SLURM_NODELIST
list of nodes that the slurm job is executing on.

.SH "BUGS"
If the number of processors per node allocated to a job is not evenly 
divisible by the value of \fBcpus\-per\-node\fR, tasks may be initiated 
on nodes lacking a sufficient number of processors for the desired parallelism. 
For example, if \fBcpus\-per\-node\fR is three, \fBnprocs\fR is four and 
the job is allocated three nodes each with four processors. The requisite 
12 processors have been allocated, but there is no way for the job to 
initiate four tasks with each of them having exclusive access to three 
processors on the same node.  The \fBnodes\fR and \fBmincpus\fR options 
may be helpful in preventing this problem. 

.SH "SEE ALSO"
\fBscancel\fR(1), \fBsqueue\fR(1)