Introduction
Throughout these modules, we assume that all code will be executed on a cluster. In this module, we will provide an example of submitting a job script to the batch scheduler.
Local vs. Cluster Environments
In the example below we will contrast running in your local environment and the cluster.
To run locally, there are two steps (assuming $p=4$ ranks):
Compile:
mpicc pingpong_comm_starter.c -lm -o pingpong_comm_starter
Run:
mpirun -np 4 -hostfile myhostfile.txt ./pingpong_comm_starter
In contrast, to use the SLURM batch scheduler, you must write a job script, as follows. For this example, assume this file is called myjobscript.sh.
#!/bin/bash
#SBATCH --job-name=ping_pong
#SBATCH --output=/path/to/scratch/myfile.out
#SBATCH --error=/path/to/scratch/myfile.err
#SBATCH --time=02:00 # 2 min
#SBATCH --mem=2000
#SBATCH --nodes=1
#SBATCH --ntasks=4
#SBATCH --cpus-per-task=1
module load openmpi
mpicc ~/path/to/work/directory/ping_pong.c -lm -o ~/path/to/work/directory/ping_pong
srun ~/path/to/work/directory/ping_pong
After you have created your script, submit your job using the command sbatch myjobscript.sh.
- Q2: How many process ranks are used in the script above?