View source for MPI hello world in C

__NOTOC__
{{back_to_tutorials}}

== Load modules ==
We will use the new software stack in this tutorial:

  [jarunanp@eu-login-10 ~]$ env2lmod  
  [jarunanp@eu-login-10 ~]$ module load gcc/6.3.0 openmpi/4.0.2
 
  The following have been reloaded with a version change:
    1) gcc/4.8.5 => gcc/6.3.0
 
  [jarunanp@eu-login-10 ~]$ which mpirun
  /cluster/apps/gcc-6.3.0/openmpi-4.0.2-4airvo32ypyuapzgi4fp2kjea5psqu3t/bin/mpirun

== MPI Hello World ==
* Go to $SCRATCH and create a work directory
  [jarunanp@eu-login-10 ~]$ cd $SCRATCH
  [jarunanp@eu-login-10 jarunanp]$ pwd
  /cluster/scratch/jarunanp
  [jarunanp@eu-login-10 jarunanp]$ mkdir test_mpi
  [jarunanp@eu-login-10 jarunanp]$ cd test_mpi
  [jarunanp@eu-login-10 test_mpi]$ 

* Download the MPI Hello World example
  [jarunanp@eu-login-10 test_mpi]$ wget -c https://gitlab.ethz.ch/jarunanp/hpc-examples/-/raw/main/mpi/c/hello_mpi.c?inline=false -O hello_mpi.c

* Compile the code
  [jarunanp@eu-login-10 test_mpi]$ mpicc -o hello_mpi hello_mpi.c

* Run the executable
  [jarunanp@eu-login-10 test_mpi]$ mpirun -np 2 hello_mpi
  Hello world from processor eu-login-10, rank 0 out of 2 processors
  Hello world from processor eu-login-10, rank 1 out of 2 processors

== Run a BSUB interactive session ==

* Request an interactive session on a compute node:
  [jarunanp@eu-login-10 test_mpi]$ bsub -n 4 -W 01:00 -Is bash
  Generic job.
  Job <155089738> is submitted to queue <normal.4h>.
  <<Waiting for dispatch ...>>
  <<Starting on eu-ms-022-14>>
  [jarunanp@eu-ms-022-14 test_mpi]$

* Run the executable
  [jarunanp@eu-ms-022-14 test_mpi]$ mpirun -np 4 hello_mpi
  Hello world from processor eu-ms-022-14, rank 0 out of 4 processors
  Hello world from processor eu-ms-022-14, rank 1 out of 4 processors
  Hello world from processor eu-ms-022-14, rank 2 out of 4 processors 
  Hello world from processor eu-ms-022-14, rank 3 out of 4 processors
  [jarunanp@eu-ms-022-14 test_mpi]$

* Exit the interactive session
  [jarunanp@eu-ms-022-14 test_mpi]$ exit
  exit
  [jarunanp@eu-login-10 test_mpi]$


== Submit a batch job with BSUB command line ==
* You can submit a job by using BSUB command line
  [jarunanp@eu-login-10 test_mpi]$ bsub -n 4 -W 10 "mpirun hello_mpi"
  MPI job.
  Job <155090084> is submitted to queue <normal.4h>.

* Check the job status
  [jarunanp@eu-login-10 test_mpi]$ bjobs
  JOBID      USER    STAT  QUEUE      FROM_HOST   EXEC_HOST   JOB_NAME   SUBMIT_TIME
  155090084  user PEND  normal.4h  eu-login-10             *llo_world Dec  8 15:53
  [jarunanp@eu-login-10 test_mpi]$

* Check the output file lsf.o155090084
  [jarunanp@eu-login-10 test_mpi]$ cat lsf.o155090084

== Create a job script ==

* Create a job script called ''job_script.bsub''

  #!/usr/bin/bash
  #BSUB -n 4
  #BSUB -W 10
  #BSUB -J test_mpi
 
  source /cluster/apps/local/env2lmod.sh
  module load gcc/6.3.0 openmpi/4.0.2
  export OMP_NUM_THREADS=0
  mpirun hello_mpi

* Submit a job using the job script
  [jarunanp@eu-login-10 test_mpi]$ bsub < job_script.bsub 
  MPI job.
  Job <155090224> is submitted to queue <normal.4h>.


{{back_to_tutorials}}