[DFTB-Plus-User] On parallel version of DFTB+
zuh101 at psu.edu
Mon Sep 19 20:01:53 CEST 2016
Can you describe some algorithm details used in DFTB+？ especially on Hamiltonian diagonalization? Tight-binding calculations are supposed to run very fast, but your reply impressed me with totally different picture. It takes me time to think over your words. I have not realized that DFTB+ might require a few thousand of processors. simply ask, could you tell me on what most CPU time are spent with DFTB+ calculation? diagonalization?
thanks a lot.
If you use iterative method to solve Hamiltonian eigenvalues as implemented in BerkeleyGW, what do you think the calculation speed?
----- Original Message -----
From: "Jacek Jakowski" <jjakowski at gmail.com>
To: "User list for DFTB+ related questions" <dftb-plus-user at mailman.zfn.uni-bremen.de>
Sent: Saturday, September 17, 2016 8:26:15 PM
Subject: Re: [DFTB-Plus-User] On parallel version of DFTB+
Most likely you don't have enough memory to fit the 26,000 atoms on
your computer, even if DFTB+ can handle it. Assuming that your
26k atoms are carbons (or similar) you need 80GB to fit a single
matrix (100kbasis) in memory and much more (like 10 times) for a real
But then if this fits into your memory, then 100k matrices on 4000
cores takes about 10 hours for a single diagonalization (real case).
It would probably took something like a month to do SCF, and
about half a year for a few MD steps.
I suggest that you decrease the size of cell so that your matrices
are below 32,000.
On Fri, Sep 9, 2016 at 1:36 PM, ZHAOHUI HUANG <zuh101 at psu.edu> wrote:
> Sorry to bother you if not interested.
> I have an issue from running parallel DFTB+. My unit cell contains 26,000 atoms and I just want to relax the structures a few steps. By running the code, I first get output overflow error message, then I increase MAXRECL parameter defined in HSDParser package. It runs indeed. but It failed by SCALAPACK error,
> MAXNEIGHBORS: 8847
> iSCC Total electronic Diff electronic SCC error
> Operation failed!
> ppotrf in scalafx_ppotrf_dreal
> Info: 23233
> Is there any code developer who is familiar with this part of code? thanks.
> ZhaoHui Huang,
> DFTB-Plus-User mailing list
> DFTB-Plus-User at mailman.zfn.uni-bremen.de
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