[CP2K:7406] Load balancing for H2O-inputs
martin.... at gmail.com
Fri Feb 5 11:39:00 CET 2016
thank you very much for that detailed answer! Since I also have some old
traces that I am wondering about: Did the load balancing in 2.x releases
work like it does in 3.0?
On Friday, February 5, 2016 at 11:05:55 AM UTC+1, IBethune wrote:
> Hi Martin,
> The load balancing algorithm in the released versions of the code (3.0 or
> earlier) can be quite memory-hungry so is turned off when running on >1024
> MPI processes. You can also override this by setting
> FORCE_EVAL%DFT%MGRID%SKIP_LOAD_BALANCE_DISTRIBUTED [TRUE|FALSE]. The fact
> that you see these routines in the timing report indicates that the load
> balancer is running. If you turn it off you will find marginally worse
> performance. For the H2O-xxx benchmarks, the atoms are essentially
> distributed at uniform density throughout the cell, so the problem is
> fairly well load balanced to start with. If you were running something
> like an isolated cluster or a slab/interface you would likely see more
> effect from using the load balancer (or not).
> Also, bear in mind that you will not get 100% load balance even when the
> load balancer is turned on as it works within certain constraints depending
> on the number of processors, the resulting decomposition of the realspace
> grids, and the system geometry. Also, the main bits of work which are
> balanced by this algorithm are the collocation and integration of gaussian
> products (calculate_rho_elec and integrate_v_rspace in the timing report).
> Other parts of the code e.g. dbcsr are not affected by the
> load_balance_distributed scheme.
> In CP2K 4.0 (development trunk), the load balancer is improved so it is
> less memory intensive and is turned on by default regardless of the number
> of MPI processes
> - Iain
> Iain Bethune
> Project Manager, EPCC
> Twitter: @IainBethune @PrimeGrid @CP2Kproject
> Web: http://www2.epcc.ed.ac.uk/~ibethune
> Tel/Fax <http://www2.epcc.ed.ac.uk/~ibethuneTel/Fax>: +44 (0)131 650
> Mob: +44 (0)7598317015
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> EH9 3FD
> > On 5 Feb 2016, at 09:57, Martin Küttler <marti... at gmail.com
> > Hi,
> > I'm using the H2O input files from cp2k/tests/QS/benchmark. In the
> output I see some times for subroutines that look like they do load
> balancing (e.g. load_balance_distributed, optimize_load_list,
> get_current_loads,...), but I don't see an effect of load balancing. Is
> there a load balancer that works for these inputs? If so, when does it kick
> in, and can it be turned on/off?
> > Thanks,
> > Martin
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