[MITgcm-devel] optim_numbmod: parameters in data.optim

[Holly Dail]

Martin -

I can't speak to your question about ff, but I did want to say this seems like a great idea to me (assuming there is no technical issue).  Like many perhaps, I have a script that does this automatically, but floating point math isn't so obvious in shell scripts so this option would be helpful for many.

Would it be more intuitive to specify the converse -- 90% instead of 10% (could call it fminFrac or fminPct).  That would fit better with the current fmin construct.

Holly

On Mar 27, 2012, at Mar 27 , 4:22 AM, Martin Losch wrote:

> Hi there,
> 
> I would like to add a new parameter to data.optim.
> Rather than specifying the expected optimized cost function value "fmin", I'd like to be able to specify a relative reduction, i.e. have something like dfmin = 0.1 for an expected decrease of 10%. This, to my mind, is much easier to do, especially, if you look at a series of optimization runs, where the initial cost function value is different between experiments by orders of  magnitude. Don't worry, fmin, will still be there and usable, I just want to add this option.
> 
> Now, for this to work I need the cost function value as computed by the model. This value is both in ecco_cost_* and ecco_ctrl_*, and it's read by optim_readdata.F (fileff), and optim_readdata is called from optim_numbmod, which would give me an easy way of computed fmin=(1-dfmin)*ff.
> But unfortunately only for the "costname"-file, ff is returned as ff=fileff, for the ctrlname-file ff=0. I was wondering, if this is really necessary, or whether I can just return ff=fileff each time optim_readdata is called. I could also choose to return it whenever lheaderonly=.true. (as it is the case when called from optim_numbmod). I have the impression, from the output of optim.x, that neither of these changes, changes the output. Would you expect any changes in the results if ff=fileff is returned to optim_numbmod?
> 
> Martin
> 
> 
> 
> 
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