Hi, On Sun, Feb 7, 2016 at 8:00 PM Johannes Wagner <[email protected]> wrote:
> hey guys, > came across an issue with pp/pme ratio difference from 5.0 to 5.1. For a > system running on 2 nodes with a pp/pme ratio of 80:16 on 5.0, the same > thing starts with 72:24 on gromacs 5.1. The 5.1 run has a much higher load > imbalance and is hence slower. Are there known changes from 5.0 to 5.1 in > the pp/pme ratio that cause this? > Yes and no. Even on only two nodes, your observations can be affected by network congestion, so I would investigate whether you can reproduce the observations. The changes that I identified that had the capacity to change performance are noted at http://manual.gromacs.org/documentation/5.1/ReleaseNotes/performance.html. For example, if you're using LINCS then the SIMD improvements there affect only the PP ranks so it might seem to the auto-tuner that it's more efficient to use fewer PP ranks. Then later some kind of load imbalance has a stronger effect. The interactions of DD DLB and PME tuning are complex, and we can't rule out that there's a problem that we should fix. But we can't say much without being able to compare some (reproducible) log files. Mark cheers, johannes > > -- > Gromacs Users mailing list > > * Please search the archive at > http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before > posting! > > * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists > > * For (un)subscribe requests visit > https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or > send a mail to [email protected]. > -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to [email protected].
