[gmx-developers] Wallcycle bug?

[Berk Hess]

No, this is clear a general x86 issue. It's described in many places on 
the web and I can easily reproduce it on my hex-core Haswell workstation.

Cheers,

Berk

On 09/15/2015 05:26 PM, Mark Abraham wrote:
> Hi,
>
> Jenkins mostly runs non-pinned mdrun, and under heavy load we probably 
> see more thread migration, and thus such de-sync events. I've only 
> seen the issue on slaves hosted under VM, so I think it's not clear 
> that this is an x86, rather than VM+x86 property.
>
> Load is heavy lately because we're running multiple master-branch 
> configs while getting the new releng machinery stable. We envisaged a 
> few days that's now been over a week, and barring this unforeseen 
> issue, I think we're more or less happy with things now. Teemu is 
> there value in dealing with more of the releng patches in gerrit 
> before we disable the old master-branch configs?
>
> Mark
>
> On Tue, Sep 15, 2015 at 5:17 PM Berk Hess <hess at kth.se 
> <mailto:hess at kth.se>> wrote:
>
>     Hi,
>
>     We didn't realize that modern x86 cpus no longer synchronize clocks
>     between cores. We should get the fix for this merged asap:
>     https://gerrit.gromacs.org/#/c/5091/
>
>     Cheers,
>
>     Berk
>
>     On 09/15/2015 05:06 PM, David van der Spoel wrote:
>     > Hi,
>     >
>     > my patch stumbled over this issue in Jenkins:
>     >
>     > Program:     gmx mdrun, VERSION 5.2-dev-20150915-ef00eb4-local
>     > Source file: src/gromacs/timing/wallcycle.cpp (line 398)
>     > Function:    void subtract_cycles(wallcc_t *, int, int)
>     >
>     > Assertion failed:
>     > Condition: wcc[ewc_main].c >= wcc[ewc_sub].c
>     > Subcounter cannot have more ticks than parent
>     >
>     > For more information and tips for troubleshooting, please check the
>     > GROMACS
>     > website at http://www.gromacs.org/Documentation/Errors
>     >
>     > Any clue? Or is this assertion just overly pedantic?
>
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