[ecco-support] Budgets in ECv4, release 3

[Martha Buckley]

You are right about the patterns being non-random. I am glad that you are
convinced!  So when will the double precision output be available online? :)
thanks,
Martha


On Mon, Nov 6, 2017 at 12:08 PM, Menemenlis, Dimitris (329C) <
Dimitris.Menemenlis at jpl.nasa.gov> wrote:

> Hi Martha, the non-random patterns in your figures
> convince me that double precision is needed.
>
> Cheers, Dimitris
>
> On Nov 6, 2017, at 8:56 AM, Martha Buckley <marthabuckley at gmail.com>
> wrote:
>
> I didn't chose the most instructive colorbar to show the magnitude of the
> errors. Attached are plots with colorbars to indicate the magnitude of the
> errors.  In particular, note that the errors due to single precision in the
> mass budget are on the order of 10% (saturated on the 1% colorbar).  Note
> these are the errors for a particular time step based on monthly output.
>
> The issue with budgets with single precision output is that the tendancy
> is always a small residual of larger terms.  While of course the
> uncertainty of ECCO estimates is larger than even these 10% errors, I think
> this is not particularly relevant to this discussion.  ECCO in the end is
> also a forward model and MITgcm developers have take great pains to insure
> that budgets close.  I don't know why we'd sacrifice the ability to close
> budgets rigorously in order to save a factor of 2 in space by storing as
> single precision.   Also, for the user it is a lot easier if the budgets
> close to machine precision rather than having a user wonder if an error is
> "acceptable" or not.
>
> Martha
>
>
>
>
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>


-- 
Martha W. Buckley
marthabuckley at gmail.com
http://sites.google.com/site/marthabuckley/home
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