[MITgcm-devel] pkg/layers verification exp.

Martin Losch Martin.Losch at awi.de
Wed Feb 6 03:53:18 EST 2013


Hi Ryan,

that's great, thanks.

For the vector machine the speedup is dramatic as usual, when scalar code is replace by vector code. In my short tests (100 time steps with a coarse global model) I get this: The original scalar code takes 270 sec (101MFLOPS, Vector operation ratio = 6%, very bad), with my modifications this goes down to 107 sec ( 217MFLOPS, Vector operation ratio = 62%). This is still very bad, but definetly better than before. Typically the important MITgcm routines go up to 10,000MFLOPS and have Vector operation ratios of over 99%. The consequence is that layers_fluxcalc even with my modifications uses 75% of the total cpu time (before it was 86%), which is still inacceptable, but the total run time goes down from 5min13sec to 2min22sec.

I didn't test anything on non-vector machines, but I assume that there won't much of a change.

I am afraid, that this diagnostic cannot completely be vectorized, but I'll ask my vectorization guru (o:

Martin


On Feb 5, 2013, at 8:45 PM, Ryan Abernathey <ryan.abernathey at gmail.com> wrote:

> Martin,
> I finally got around to trying your changes to the layers code: the output looks fine to me. Please go ahead and check this in.
> Did you get a chance to do any benchmarking? Is the new code faster or slower?
> -Ryan
> 
> 
> On Wed, Jan 9, 2013 at 2:02 AM, Martin Losch <Martin.Losch at awi.de> wrote:
> OK, it's not exactly urgent anyway.
> 
> Martin
> 
> On Jan 8, 2013, at 11:33 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:
> 
> > Hi Ryan and others,
> >
> > Will start to make changes in cfc_example to add a pkg/layers test
> > (working with David on this).
> > Will need to make few changes in pkg/layers so that it compiles
> > in this set-up.
> > Martin, if you can postpone your changes until this is done,
> > it will make things easier.
> >
> > Cheers,
> > Jean-Michel
> >
> > On Tue, Jan 08, 2013 at 11:25:32AM -0500, Ryan Abernathey wrote:
> >> I am not super familiar with these experiments, but I think the cfc_example
> >> is a better choice. What would really be ideal is an eddying experiment,
> >> but this is probably not practical for the daily test reports. Certainly an
> >> experiment with a realistic stratification and overturning is a necessity.
> >> Someone else (Martin / David / Ross / Jean-Michel) would probably be better
> >> than me at setting this up. The fact is that I don't run realistic global
> >> models. I am still stuck in a channel with no salinity! Layers has evolved
> >> quite a bit beyond my original setup.
> >>
> >> A nice accompaniment to this would be some real documentation. I have
> >> promised to work on this for quite some time, but it's one of those things
> >> that is hard to prioritize. ;)
> >>
> >> I have many ambitions for the future of layers. For example, I would love
> >> to be able to accumulate all the tracer-budget diagnostics that are filled
> >> in gad_advection.F in layer space. This would permit, for example, the
> >> online calculation of water mass transformation with an unprecedented level
> >> of precision. I am very glad that all you numerical wizards are getting
> >> involved because I will need your help to go down that road! The final
> >> step, the momentum budget in layer space, is pretty intimidating. And at
> >> that point you are probably better off just running GOLD. ;)
> >>
> >> Cheers,
> >> Ryan
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> On Mon, Jan 7, 2013 at 9:46 AM, Jean-Michel Campin <jmc at ocean.mit.edu>wrote:
> >>
> >>> Hi Ryan, David, Martin and others,
> >>>
> >>> In response to Martin's concern about having an example that uses
> >>> pkg/layers,
> >>> I would propose to turn it on in one of the verification experiment.
> >>>
> >>> Right now, it's already compiled in exp4, but given the simple
> >>> T,S structure (+ only 8 levels) of this experiment, I was wondering
> >>> if we should rather pick an other experiment, may be a realistic set-up ?
> >>>
> >>> In term of realistic set-up, I would propose cfc_example, 2.8 x 2.8 global
> >>> with 15 levels, starting from a pickup.
> >>> It is not too complicated (does not test too many critical features),
> >>> and also adding pkg/layers will not make it less clear the "cfc example"
> >>> part,
> >>> I think.
> >>>
> >>> But if exp4 is good enough to test pkg/layers, could just go with this one.
> >>>
> >>> What do you think ?
> >>>
> >>> Cheers,
> >>> Jean-Michel
> >>>
> >>> _______________________________________________
> >>> MITgcm-devel mailing list
> >>> MITgcm-devel at mitgcm.org
> >>> http://mitgcm.org/mailman/listinfo/mitgcm-devel
> >>>
> >
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> >
> >
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