Colombia 2024

General instructions to run tutorials

Computational resources are managed by the job scheduling system Slurm. Most part of Yambo tutorials during this school can be run in serial, except some that need to be executed on multiple processors. Generally, Slurm batch jobs are submitted using a script, but the tutorials here are better understood if run interactively. The two procedures that we will use to submit interactive and non interactive jobs are explained below.

Run a job using a batch script

One option is to submit the job using a batch script job.sh, whose generic structure is the following:

$ more job.sh
#!/bin/bash
#SBATCH --account=tra24_ictpcolo        # Charge resources used by this job to specified account
#SBATCH --time=00:10:00                 # Set a limit on the total run time of the job allocation in hh:mm:ss
#SBATCH --job-name=JOB                  # Specify a name for the job allocation
#SBATCH --partition= dcgp_usr_prod      # Request a specific partition for the resource allocation
#          
#SBATCH --nodes=<N>                     # Number of nodes to be allocated for the job
#SBATCH --ntasks-per-node=<nt>          # Number of MPI tasks invoked per node
#SBATCH --ntasks-per-socket=<nt/2>      # Tasks invoked on each socket
#SBATCH --cpus-per-task=<nc>            # Number of OMP threads per task

module purge
module load profile/chem-phys
module load yambo/5.2.2--intel-oneapi-mpi--2021.10.0--oneapi--2023.2.0

export OMP_NUM_THREADS=<nc>
mpirun --rank-by core -np ${SLURM_NTASKS} yambo -F <input> -J <output>

To submit the job, use the sbatch command:

$ sbatch job.sh
Submitted batch job <JOBID>

To check the job status, use the squeue command:

$ squeue -u <username>
             JOBID PARTITION     NAME     USER ST       TIME  NODES NODELIST(REASON)
             <...>  ...      JOB username  R       0:01    <N> <...>

If you need to cancel your job, do:

$ scancel <JOBID>

Open an interactive session

This procedure is suggested for most of the tutorials, since the majority of these is meant to be run in serial (relatively to MPI parallelization) from the command line. Use the command below to open an interactive session of 1:30 hour (complete documentation here):

$ srun --nodes=1 --ntasks-per-node=4 --cpus-per-task=8 --account=tra24_ictpcolo --partition=dcgp_usr_prod --time=1:30:00 --gres=tmpfs:10g --pty /bin/bash
srun: job 8338413 queued and waiting for resources
srun: job 8338413 has been allocated resources
[username@lrdn4735 ~]$

We ask for 4 cpus-per-task because we can exploit OpenMP parallelization with the available resources.

username@lrdn4735$ cd $SCRATCH

Then, you need to manually load yambo as in the batch script above. Please note that the serial version of the code is in a different directory and does not need spectrum_mpi:

$ module purge
$ module load profile/chem-phys
$ module load yambo/5.2.2--intel-oneapi-mpi--2021.10.0--oneapi--2023.2.0

Finally, set the OMP_NUM_THREADS environment variable to 4 (as in the --cpus-per-task option):

$ export OMP_NUM_THREADS=4

To close the interactive session when you have finished, log out of the compute node with the exit command, and then cancel the job:

$ exit

DAY 1 - Monday, October 18^th

9:00 - 9:45 Density-Functional Theory: Basic concepts and approximations

14:00 - 14:45 Many-Body Perturbation theory: Basic concepts and approximations

14:45 - 15:00 Yambo Technical Introduction and Philosophy

15:00 - 17:30 From the DFT ground state to the complete setup of a Many Body calculation using Yambo

To get the tutorial files needed for the following tutorials, follow these steps:

$ wget https://media.yambo-code.eu/educational/tutorials/files/hBN.tar.gz
$ wget https://media.yambo-code.eu/educational/tutorials/files/hBN-2D.tar.gz
$ ls
hBN-2D.tar.gz  hBN.tar.gz
$ tar -xvf hBN-2D.tar.gz
$ tar -xvf hBN.tar.gz
$ ls
hBN-2D hBN hBN-2D.tar.gz  hBN.tar.gz

Now that you have all the files, you can proceed with the tutorials.

• First steps: Initialization and more
• Next steps: RPA calculations

DAY 2 - Tuesday, October 19^th

14:00 - 16:30 A tour through GW simulation in a complex material (from the blackboard to numerical computation: convergence, algorithms, parallel usage)

To get all the tutorial files needed for the following tutorials, follow these steps:

wget https://media.yambo-code.eu/educational/tutorials/files/hBN.tar.gz
wget https://media.yambo-code.eu/educational/tutorials/files/MoS2_2Dquasiparticle_tutorial.tar.gz
tar -xvf hBN.tar.gz
tar -xvf MoS2_2Dquasiparticle_tutorial.tar.gz
cd hBN

Now you can start the first tutorial:

• GW computations on practice: how to obtain the quasi-particle band structure of a bulk material

If you have gone through the first tutorial, pass now to the second one:

cd $CINECA_SCRATCH
cd YAMBO_TUTORIALS
cd MoS2_HPC_tutorial

• Quasi-particles of a 2D system

Lectures

DAY 1 - Monday, 22 May

• G. Stefanucci, The Many-Body Problem: Key concepts of the Many-Body Perturbation Theory
• M. Marsili, Beyond the independent particle scheme: The linear response theory

DAY 2 - Tuesday, 23 May

• E. Perfetto, An overview on non-equilibrium Green Functions
• R. Frisenda, ARPES spectroscopy, an experimental overview
• A. Marini, The Quasi Particle concept and the GW method
• A. Guandalini, The GW method: approximations and algorithms
• D.A. Leon, C. Cardoso, Frequency dependence in GW: origin, modelling and practical implementations

DAY 3 - Wednesday, 24 May

• A. Molina-Sánchez, Modelling excitons: from 2D materials to Pump and Probe experiments
• M. Palummo, The Bethe-Salpeter equation: derivations and main physical concepts
• F. Paleari, Real time approach to the Bethe-Salpeter equation
• D. Sangalli, TD-HSEX and real-time dynamics

DAY 4 - Thursday, 25 May

• S. Mor, Time resolved spectroscopy: an experimental overview
• M. Grüning, Nonlinear optics within Many-Body Perturbation Theory
• N. Tancogne-Dejean, Theory and simulation of High Harmonics Generation
• Y. Pavlyukh, Coherent electron-phonon dynamics within a time-linear GKBA scheme