...
| Codeblock |
|---|
| language | bash |
|---|
| title | Looping over multiple inputs |
|---|
| collapse | true |
|---|
|
$ parallel --xapply echo {1} {2} ::: 1 2 3 ::: a b c
1 a
2 b
3 c
$ parallel echo {1} {2} ::: 1 2 3 ::: a b c
1 a
1 b
1 c
2 a
2 b
2 c
3 a
3 b
3 c |
Doing local I/O tasks in parallel
To distribute data from a global location ($WORK, $HOME) to several nodes simultaneously - similar to a MPI_Bcast - one can use:
| Codeblock |
|---|
| language | bash |
|---|
| title | pdcp ex. |
|---|
|
pdcp -r -w $SLURM_NODELIST $WORK/input2copy/* $LOCAL_TMPDIR |
$LOCAL_TMPDIR exists - only "node" locally - on all compute nodes (see Special Filesystems for more details).
To collect individual data from several node-local locations simultaneously - similar to a MPI_Gather - one can use:
| Codeblock |
|---|
| language | bash |
|---|
| title | rpdcp ex. |
|---|
|
rpdcp -r -w $SLURM_NODELIST $LOCAL_TMPDIR/output2keep/* $WORK/returndir |
Automatically, rpdcp will rename the data by appending the local hostname of its origin. This avoids overwriting of files with the same name.
In the next example local output data ($LOCAL_TMPDIR) is moved back to $WORK while the main program is still running. With "&" you send the main program in the background.
| Anker |
|---|
| local_tmpdir_example |
|---|
| local_tmpdir_example |
|---|
|
| Codeblock |
|---|
| language | bash |
|---|
| title | moving $LOCAL_TMPDIR data on-the-fly using pdsh and pdcp |
|---|
|
#!/bin/bash
#SBATCH --partition=cpu-genoa:test
#SBATCH --nodes=2
#SBATCH --tasks-per-node=3
#SBATCH --job-name=auto_loc_io_test
#SBATCH --output=%x.%j.out
echo ""
echo "Used environment variables:"
echo "WORK" $WORK
echo "LOCAL_TMPDIR" $LOCAL_TMPDIR
# Auto set by Slurm prolog: /local/$USER_$SLURM_JOB_ID
echo ""
echo "Used slurm variables:"
echo "SLURM_JOB_NAME" $SLURM_JOB_NAME
echo "SLURM_JOB_ID" $SLURM_JOB_ID
echo "SLURM_NODELIST" $SLURM_NODELIST
echo ""
### prepare case
# master dir. on global filesystem
# can be created by master node (= directly this script)
MASTERDIR=$WORK/$SLURM_JOB_NAME"."$SLURM_JOB_ID
echo "All job data is (collected) here: $MASTERDIR"
# subdirectories of master dir.
# can be created by master node (= directly this script)
INPUT_DIR=$MASTERDIR/in
OUTPUT_DIR=$MASTERDIR/allout
mkdir -p $INPUT_DIR
mkdir -p $OUTPUT_DIR
echo "example data inside input file" > $INPUT_DIR/input_data.dat
# $LOCAL_TMPDIR (aka /local/$USER_$SLURM_JOB_ID)
# is dir. on node-local ssd or ram if no ssd is present
# only exist during job lifetime
# subdirectories of $LOCAL_TMPDIR
# can only be created node-locally (= "child" srun -w node)
LOC_OUT_DIR=$LOCAL_TMPDIR/out
# prepare script with empty 10 second job
cat <<EOF > $INPUT_DIR/dummyjob.sh
#!/bin/bash
echo "Main job started on \$SLURMD_NODENAME in \$PWD."
sleep 10
mkdir -p $LOC_OUT_DIR
hostname > $LOC_OUT_DIR/data.\$SLURMD_NODENAME
# important to use unique local name in order to mv it to global dir. without overwriting
echo "\$SLURMD_NODENAME main job finished. Data written to $LOC_OUT_DIR."
EOF
chmod u+x $INPUT_DIR/dummyjob.sh
# command to cp data from global master to tempory local
# before mv -> check if dir is present and if not empty (=data to copy inside)
loc2mst_cmd_string='if [ -d '$LOC_OUT_DIR' ]; then if ! [ $(find '$LOC_OUT_DIR' -maxdepth 0 -empty) ]; then mv '$LOC_OUT_DIR'/* '$OUTPUT_DIR'; fi; fi'
# All ifs/checks are only needed to avoid warnings triggered for example if no data to mv is present...
### cp input files to node-local directories (in parallel)
pdcp -r -w $SLURM_NODELIST $INPUT_DIR/* $LOCAL_TMPDIR
echo "Relevant data is copied to node-local locations. Main job is starting..."
### execute main job itself: e.g. mpirun or srun
srun $LOCAL_TMPDIR/dummyjob.sh &
main_pid=$!
echo "Main job running. Start copying node-local data back to global filesystem in the background - every three seconds..."
while ps -p $main_pid &>/dev/null; do
echo "Capacity of \$LOCAL_TMPDIR is:"
df -h $LOCAL_TMPDIR
pdsh -w $SLURM_NODELIST "$loc2mst_cmd_string"
echo "loc2mst cmd executed. New capacity of \$LOCAL_TMPDIR is:"
df -h $LOCAL_TMPDIR
sleep 3
done
wait
echo "Main job finished. Copying remaining node-local data (if any)."
pdsh -w $SLURM_NODELIST "$loc2mst_cmd_string"
echo "All (parallel) copy jobs are done. All data is here: $MASTERDIR" |