composition of exciton by ypp

Anything regarding the post-processing utility (e.g. excitonic wavefunction analysis) is dealt with in this forum.

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caowd
Posts: 22
Joined: Mon Jan 20, 2014 4:13 am

Re: composition of exciton by ypp

Post by caowd » Tue Mar 01, 2016 4:36 pm

Dear Daniele Varsano

The problem has been solved by reducing the BSK Dimension according to previous discussions in the forum.

Best Wishes.
Wen-Dong Cao
Candidate for Ph.D
Department of Physics
Group of Condensed Material Theory
Tsinghua University
Beijing P.R.China
+86 010 62772784

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Daniele Varsano
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Re: composition of exciton by ypp

Post by Daniele Varsano » Tue Mar 01, 2016 5:06 pm

Dear Wen-Dong,
looking at you report you are try to diagonalize an enormous matrix more than 200Kx 200K. Most probably there are problem of memory allocation.

Code: Select all

|Dimension               : 256000
|Bands                   :  9  24
This is impossible with traditional method.
You can either:
1) Diagonalize it with iterative methods by setting in the input file : BSSmod= "h"
But note that in this way you will have access to the spectrum but not to the eigenvector so that you cannot see the composition of the excitation.

2) Try to reduce your matrix by reducing the BSE bands. Note you have 4000 points in the entire BZ, so the dimension of the matrix become very large when adding bands.
The dimension is Nk x Nv x Nc, and consider that diagonalize a matrix let's say larger than 20k x 20k become very demanding. Try to see if you can converge it with very few bands, or may be you can use a smaller k sampling.

Best,

Daniele


Addendum: I answered your post before looking your last post. Great to know you solved.
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

haseebphysics1
Posts: 169
Joined: Sat Aug 17, 2019 2:48 pm

Re: composition of exciton by ypp

Post by haseebphysics1 » Sun Apr 05, 2020 8:00 am

Dear Daniele,

I am also facing the issue of disk space storage of large BS matrix, so as was suggested in this thread that we can use the following to avoid disk-IO:

DBsIOoff= "BS"
But in my case BS matrix is still being written in a large file (ndb.BS_PAR_Q1) (more than 290 GB) and I am unable to proceed due to disk storage quota!

I am using yambo-4.5.1, compiled with HDF5 support.

I added manually the following lines in the input:

Code: Select all

StdoHash=  40                  # [IO] Live-timing Hashes
DBsIOoff= "BS"               # [IO] Space-separated list of DB with NO I/O. DB 
 (DIP,X,HF,COLLs,J,GF,CARRIERs,OBS,W,SC,BS,ALL)
DBsFRAGpm= "none"              # [IO] Space-separated list of +DB to FRAG and -DB to NOT FRAG. DB=(DIP,X,W,HF,COLLS,K,BS,QINDX,RT,ELP
#WFbuffIO                      # [IO] Wave-functions buffered I/O

Thanks,
Haseeb Ahmad
MS - Physics,
LUMS - Pakistan

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Daniele Varsano
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Re: composition of exciton by ypp

Post by Daniele Varsano » Mon Apr 06, 2020 7:31 am

Dear Haseeb,
this is happening because this feature was not added for the hdf5 support.
Applying the patch attached here (thanks Davide!) the DBsIOoff= "BS" should work also for the hdf5 support.

Best,
Daniele
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Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

haseebphysics1
Posts: 169
Joined: Sat Aug 17, 2019 2:48 pm

Re: composition of exciton by ypp

Post by haseebphysics1 » Mon Apr 06, 2020 10:58 am

Thank you, developers!


Regards,
Haseeb Ahmad
MS - Physics,
LUMS - Pakistan

haseebphysics1
Posts: 169
Joined: Sat Aug 17, 2019 2:48 pm

Re: composition of exciton by ypp

Post by haseebphysics1 » Sat Jun 19, 2021 2:33 pm

.
Haseeb Ahmad
MS - Physics,
LUMS - Pakistan

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