Dear Axel This was just a proposal. If I am right, Terachem code can use gaming cards for GPU calculations (I saw some of its authors' papers). As you know, the main problem of GTX cards comes back to two important things. One, single precision, and the other lack of ECC.
It is not necessary to write a stand alone code. We can test the QE-GPU with both TESLA and/or GTX and QE (cpu only), and compare the outputs. I tested it for only one case (rutile 3*3*2 supercell), and saw that the GTX output is similar to the CPU one. However, It is needed to test for different cases and different clusters to be sure that the lack of ECC and double precision has no effect on results. As Filippo said formerly for GTX cards, the output may be not reproducible. However, I think due to the nature of SCF algorithm, the code can be used at least for VC-RELAX, RELAX, and SCF types of calculations with GTX cards. Of course, it should be tested. Thank you for your interest. With the Best Regards Reza Behjatmanesh-Ardakani Associate Professor of Physical Chemistry Address: Department of Chemistry, School of Science, Payame Noor University (PNU), Ardakan, Yazd, Iran. E-mails: 1- reza_b_m_a at yahoo.com (preferred), 2- behjatmanesh at pnu.ac.ir, 3- reza.b.m.a at gmail.com. -------------------------------------------- On Fri, 6/20/14, Axel Kohlmeyer <akohlmey at gmail.com> wrote: Subject: Re: [Pw_forum] A "relax" input runs on CPU (pw.x) but not on CPU-GPU (pw-gpu.x) To: "PWSCF Forum" <pw_forum at pwscf.org> Date: Friday, June 20, 2014, 2:19 PM On Fri, Jun 20, 2014 at 4:22 AM, Reza Behjatmanesh-Ardakani <reza_b_m_a at yahoo.com> wrote: > Dear Filippo > > Due to the nature of QE which is iterative, I think lack of ECC and even double precision floating point in gaming cards (GTX) comparing to tesla cards > > is not serious problem for QE-GPU. Some authors have checked this for AMBER molecular dynamics simulation code. See following site: classical MD is a very different animal than what you do with QE. errors due to single precision to some properties in classical MD are huge with all single precision calculations. to compute a force from a distance will not be much affected, but summing up the force can already be a problem. "good" classical MD codes usually employ a mixed precision approach, where only the accuracy insensitive parts are done in single precision. for very large system, even double precision can show significant floating point truncation errors. usually you are dependent on error cancellation, too, i.e. when you study a simple homogenous system (as it is quite common in those tests). > > http://www.hpcwire.com/2014/03/13/ecc-performance-price-worth-gpus > > > and see the following paper: > > > www.rosswalker.co.uk/papers/2014_03_ECC_AMBER_Paper_10.1002_cpe.3232.pdf > > > > I encourage the users of QE-GPU to test it for QE, and report the difference on the site. it is a waste of time and effort. people have done DFT and HF in (partial) single precision before and only if you write a new code from scratch and have an extremely skilled programmer, you will succeed. have a look at the terachem software out of the group of todd martinez for example. axel. > PS: to be able to test the results for GTX and TESLA, it is needed QE-GPU code to be run on GTX :-) > > > With the Best Regards > >? ? Reza Behjatmanesh-Ardakani >? ? Associate Professor of Physical Chemistry >? ? Address: >? ? Department of Chemistry, >? ? School of Science, >? ? Payame Noor University (PNU), >? ? Ardakan, >? ? Yazd, >? ? Iran. >? ? E-mails: >? ? ? ? ???1- reza_b_m_a at yahoo.com (preferred), >? ? ? ? ???2- behjatmanesh at pnu.ac.ir, >? ? ? ? ???3- reza.b.m.a at gmail.com. > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Dr. Axel Kohlmeyer? akohlmey at gmail.com? http://goo.gl/1wk0 College of Science & Technology, Temple University, Philadelphia PA, USA International Centre for Theoretical Physics, Trieste. Italy. _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://pwscf.org/mailman/listinfo/pw_forum