[Pw_forum] ph.x: Avoiding the recalculation of the band structure in distributed phonon dispersion jobs

[Karttunen Antti]

Dear Andrea,

Thank you very much for the bug fix and introducing the low_directory_check input variable. Now the process goes very smoothly and we can avoid all the unnecessary band calculations in the future.

I noticed that there is still some problem with the GRID_example run_example_3: Looking at the reference output files, epsilon and bands are actually recalculated at every q. I ran the example and it seems that there is some problem with the management of the temporary directories. The example actually runs nicely, if one completely omits the creation of the separate $q.$irr directories and just runs with one single _ph0 directory with one $prefix.phsave and all the qdirs. 

I also noticed that the run_example_3 always tries to keep the qdir of the last q-point in the current temp directory:
  cp -r $TMP_DIR/_ph0/$PREFIX.q_8 $TMP_DIR/$q.$irr/_ph0/
I guess the reason for this is that without this, ph.x crashes for q<8 because seqopn fails for $prefix.q_8/recover? I encountered this with my own tests, too. It seems that after the only_init run, CURRENT_Q in status_run.xml is set to the last q-point and ph.x would then like to have $prefix.q_8 directory around in the following (q,irr) calculations. I'm planning that I don't want to move all qdirs into every (q,irr) _ph0 directory, so after the only_init run, I will reset the CURRENT_Q to 1 in my scripts. For example something like

sed -r -i '/<CURRENT_Q/,/<\/CURRENT_Q/s/[[:digit:]]+[[:space:]]*$/1/' _ph0/$prefix.phsave/status_run.xml

works nicely. Or maybe ph.x could reset CURRENT_Q to 1 in the end of a successful only_init-run? But this might have some side effects I'm not aware of, so I'm also fine with using the above script. Anyway, thanks a lot for all the great work with the grid implementation, this will enormously speed up our work on the phonon calculations of large systems.

Best wishes,
Antti

-- 
Dr. Antti Karttunen
Department of Chemistry
University of Jyväskylä, Finland
Tel: +358-50-3473475
WWW: http://www.iki.fi/ankarttu 

-----Original Message-----
From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On Behalf Of Andrea Dal Corso
Sent: Tuesday, February 26, 2013 4:19 PM
To: PWSCF Forum
Subject: Re: [Pw_forum] ph.x: Avoiding the recalculation of the band structure in distributed phonon dispersion jobs

> Thank you for your help in identifying bugs. Now I have commited a bug
> fix to check_directory_phsave.