Nicola et al., I am attempting to setup such a test under controlled conditions.
It would be helpful to clarify a point, because we want to avoid comparing apples with oranges. There are two ways to solve for the KS ground state. 1. Direct minimization of KS functional 2. Self-consistently solving the KS eqn. The conjugate-gradient (cg) in PWSCF and CP are not doing different things same thing. In PWSCF we are doing #2, while in CP we are doing #1. What would best for comparison purposes then? Have each do 10 iterations with CG using random wavefunctions as a starting guess. I would think that even with those settings that PWSCF still has the advantage due to have startingpot = atomic. Hopefully, I am not saying jibberish. I having not thought how the PW codes work in a while so I am rusty. On 2/15/07, Nicola Marzari <marzari at mit.edu> wrote: > > > > Paolo Umari has also implemented a conjugate gradients minimization > in CP. > > so, for a CP calculation, in which the only thing you need is the > electronic ground state of a given structure, this would be the best > strategy - our few tests were that it was 3-4 times more effective than > damped dynamics. If you want to relax a structure, you should do, after > this first electronic calculation, a combined damped dynamics on > electrons and ions. > > One thing we haven't tested is the relative performance of PWSCF and > CP - my guess is that the algorithms of PWSCF are much faster, although > the balance might change as the system becomes larger and larger. > In principle, the CP algorithm is variational, so should always > converge, but again this is rarely a problem. > > Bottom line - advantages for PWSCF is that it should be faster for most > systems of interest. CP uses much less memory, and should be very > efficient in calculating H|psi>, so the balance when going towards very > large scale or very parallel calculations would be extremely interesting > to explore. > > Any comparative test, under controlled conditions, would be very useful. > > nicola > > > Paolo Giannozzi wrote: > > > > On Feb 14, 2007, at 18:48 , Nichols A. Romero wrote: > > > >> If one were to use CP across such a large number of processors, > >> what algorithm is your best bet for minimizing your electronic d.o.f., > >> sd or cg > > > > steepest descent is very inefficient and should be used only > > for the initial steps of a simulation or in desperate cases. The > > "standard" way of minimizing electronic degrees of freedom > > in CP is damped dynamics > > > > Paolo > > --- > > Paolo Giannozzi, Democritos and University of Udine, Italy > > > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > -- > --------------------------------------------------------------------- > Prof Nicola Marzari Department of Materials Science and Engineering > 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA > tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Nichols A. Romero, Ph.D. 1613 Denise Dr. Apt. D Forest Hill, MD 21050 443-567-8328 (C) 410-306-0709 (O) -------------- next part -------------- An HTML attachment was scrubbed... URL: /pipermail/attachments/20070215/1716f31f/attachment.htm
