[QE-users] Question about restarting relaxation jobs

Mon Jul 8 18:43:50 CEST 2019

Thank you so much Pietro

May I ask one more question?

1) This is just double checking question. I checked the folder where the relaxation was stopped by cluster due to wall time limit (I didn't set max seconds). In the output folder, I can see prefix.save/ folder and pwscf.save/ folder, and prefix.update and prefix.bfgs file. But because I have no prefix.EXIT folder neither prefix.EXIT file, I cannot restart this simulation. Is this correct?

2) Now I'm setting "max_seconds" to all my QE DFT works. But I found that CPU time and wall time is slightly different. From my recent finished calculation, it is written at the end of the  output file:

PWSCF        :   4d21h44m CPU   4d22h12m WALL
   This run was terminated on:  21:27:26   1Jul2019

I used 30 cores, and set 7 days of wall time. Simulation finished before wall time, but I'm not sure why this slight difference of CPU time and wall time occur.
In this case, what would be the good time of max seconds CPU time when compared to wall time? If I request 7 days of wall time to cluster, then would it be more "safe" to set 6 days or 6.5 days of CPU time for max seconds?

3) This is also double checking question. If I wish to start the restart in same folder, I would better to change prefix from "SimulatinoA" to "SimulationA_restart1", would it be OK?  Also, if I wish to use different folder, I need to copy entire files inside prefix.EXIT folder to the new restart folder, is this correct?

Thank you so much for friendly answers to beginner question!!

________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Pietro Davide Delugas <pdelugas at sissa.it>
Sent: Monday, July 8, 2019 4:14:06 AM
To: users at lists.quantum-espresso.org
Subject: Re: [QE-users] Question about restarting relaxation jobs

Hello

1)  and 2) PW writes the restart files only when it terminates before convergence is reached either because the max number of steps (and the  max number may be  either the number of  electronic steps during scf of  number of ionic steps during structural relaxation) or the the execution time exceed  max_seconds specified in input or because the user has stopped the calculation creating a file in the outdir called prefix.EXIT.

If restart_mode in &control is set to "restart"  pw will try to restart the relaxation from the last POSITIONS  which have been saved in the prefix.save directory using the last saved charge density and wave functions. If it finds the restart files it will use them also. This mechanism works fine if positions, charge density and wave functions  data have been saved regularly,  but if the calculation is going to be stopped abruptly, for example by the job manager,  there is no way to prevent that the stop arrives when the program is writing these data. The safer way to go when you are using a job manager is to set the max_seconds variable to a number consistently lower than the time allocated by the job manager, the difference between these two times should be enough to allow to the program to pass through one of the check_points at which, during execution, it checks if the execution time has exceeded the max_seconds s or if the user has created a prefix.EXIT file. To estimate how long should be the difference between max_seconds and the scheduled execution time check how long it takes to the program to make an scf loop, this one will  a very safe estimate, you could reduce this time significantly and things should be working.

3) I don't understans what you want to do. You create the prefix.EXIT file when you want to stop your calculation and you want the calculation to finish smoothly saving all restart information so that it can resatart from more or less the same point when it was interrupted. It is completely senseless to rename  the output file as prefix.EXIT because it will make the program to stop as soon as a check_point detects the file and the file will be deleted. The only thing that you have to do when restarting a calculation is

  *     Specify restart_mode = 'restart' in the input.in file

  *     take care that the information saved in output.out is not rewritten by the new execution just use something as     mpirun pw.x  < input.in >> output.out which appends the new output to the old one or redirect the output to files with different names

4)   outdir must be the same or if you want to use a different one you have to create the new outdir befor restarting and copy there all the data of the previous calculation i.e. the prefix.save directory.

5) don't complicate things too much

Pietro

On 7/6/19 3:59 PM, Yeon, Jejoon wrote:

Hello

I have very small amount of experience using QE, so please excuse my beginner question. I'm about to start relaxation of big crystal structure, and I wish to make my QE relaxation jobs ready for restart. Here are my questions:

1) According to "restarting" section from manual, (https://www.quantum-espresso.org/Doc/pw_user_guide/node20.html) it seems that QE does not creates the dedicated restart file, is this correct?

2) If I set up "max_seconds" option as 604800 seconds (1 week), and request wall time to server 1 week, do my calculation jobs are ready to restart after 1 week? (1 week is just example but our server cluster have maximum some walltime limitation, and I don't think any of my relaxation works will be finished within that time. ) Also, does this "max_seconds" option must be required to restart?

3) When I execute QE in the submit script, I use something similar as:
mpirun pw.x  < input.in > output.out
In this case, if the relaxation job is killed due to wall time limit (without setting max_seconds), can I just change the name of the output.out to prefix.EXIT, (of course I set up prefix in the input file) and then include restart_mode = "restart" in the input file, then submit a job for restart?
I have old files which are finished after reaching wall time limit without "max_seconds" option, and I'm curious if I can use those files to restart.

4) I also use outdir option in the input file, does the outdir option should be the same when restart?

5) Are there any other things or useful hints that I need to consider when restart?

Thank you

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