Continous timeout for Phonon Calculation (Hessian Matrix and Dielectric function)

[enochho]

Hi all,

My goal is to model the refractive index in Terahertz and infrared ranges for a few organic crystals, thus I would to calculate the hessian matrix and the dielectric function with VASP. So, I submitted a job with IBRION = 6 (I also have my setup parameters in the end). However the calculation kept being timeout due to the wall time limit (50hrs) of the supercomputer that I use, and I have been resubmitting it again and again with an existing WAVECAR for 4 times now. I am just wondering if this kind of calculation to get hessian matric and dielectric function indeed takes so long or I am not restarting it correctly. I also see a comment in ResearchGate forum saying that this type of calculation could not be restarted, is it the case? (Bogdanovski, Dimitri. (2020). Re: Restart VASP job with IBRION=6?. Retrieved from: https://www.researchgate.net/post/Resta ... n/download.)

Below are my calculation steps:
I first converted a cif file to a POSCAR file with VESTA by outputting the current unit cell. Then I performed 4 consecutive relaxations (IBRION = 2) until the external pressure is below 1kb. After that, I submitted the job to calculate the hessian matrix and dielectric function with k-point mesh of 3x3x3 and with the below setup:
ISYM = 0
PREC = Accurate
ENCUT = 400
ISIF = 7
IBRION = 6
EDIFFG = -0.0001
IALGO = 38
NFREE = 2
POTIM = 0.015
ISMEAR = 0;
SIGMA = 0.1
GGA = PS
LEPSILON = .TRUE.
NCORE = 2
NSIM = 4
LREAL = Auto
LOPTICS = .TRUE.

I would appreciate any feedbacks or suggestions, thanks.

[merzuk.kaltak]

Dear enochho,

Please submit POSCAR, the incomplete OUTCAR and your job script.
If you run vasp_std or vasp_ncl, please also include KPOINTS file in your upload.

[enochho]

Thanks for your response. Here are the files for one of the jobs I tried to run. The jobs just got timeout again this morning and this is the sixth time I submitted the job (I first submitted the job on the 8th of Feb). I also attached the generated WAVECAR file because I noticed that the WAVECAR files is empty with 0kb, and I am guess it might also be the reason the job do not get restarted correctly. Thanks.

[andreas.singraber]

Hello!

Sorry for the delayed answer! I had a look at your files and I think you have one major mistake in the job script which causes this surprisingly bad performance: you are not running VASP with MPI parallelization but only with OpenMP threading. This can be seen from the OUTCAR lines at the very beginning:

Code: Select all

running    1 mpi-ranks, with   64 threads/rank

Also in your job script you specify:

Code: Select all

export OMP_NUM_THREADS=$SLURM_CPUS_ON_NODE
...
/fslhome/enochho/fsl_groups/fslg_jsl_vasp/VASP_code/vasp.6.3.2/bin/vasp_std

Hence you set the number of OpenMP threads to 64 and then invoke VASP without mpirun or srun. So VASP uses only a single MPI rank and 64 OpenMP threads. This will be highly inefficient as VASP relies on MPI as major parallelization method. OpenMP can be optionally added on top in a hybrid parallelization setup as explained here.

For the moment I would suggest not to use any OpenMP threading and instead fix the MPI parallelization. I do not know how your HPC cluster is set up so I can only guess how this should be done in your job script, but maybe this will get you started:

Code: Select all

export OMP_NUM_THREADS=1
...
mpirun -np 64 /fslhome/enochho/fsl_groups/fslg_jsl_vasp/VASP_code/vasp.6.3.2/bin/vasp_std

Or, alternatively, just use srun instead of mpirun -np 64. The first lines of the OUTCAR files should then look like this:

Code: Select all

running   64 mpi-ranks, with   1 threads/rank

If this works you can check the timings in the OUTCAR (search for the string LOOP and LOOP+) file and compare them to your previous attempts. There should be a major improvement! In any case please consult the documentation of your HPC center to check out the correct way of running MPI parallelized applications.

Hope this helps, all the best,
Andreas Singraber