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Posted to dev@commons.apache.org by Luc Maisonobe <Lu...@free.fr> on 2011/09/01 20:36:42 UTC
Re: [Math] Jacobian dimensions in "AbstractLeastSquaresOptimizer"
Le 31/08/2011 18:09, Gilles Sadowski a écrit :
> Hello.
Hi Gilles,
>
> In the "AbstractLeastSquaresOptimizer" class (package "optimization"), there
> is (at lines 238-247):
> ---CUT---
> jF = f.jacobian();
> this.residuals = new double[target.length];
>
> // Arrays shared with the other private methods.
> point = startPoint.clone();
> rows = target.length;
> cols = point.length;
>
> weightedResidualJacobian = new double[rows][cols];
> this.weightedResiduals = new double[rows];
> ---CUT---
>
> Is it necessary to impose the layout of "jF"? Indeed, depending on the
> implementation of the "jacobian()" method, one could have
> ---CUT---
> rows = point.length;
> cols = target.length;
> ---CUT---
> instead. And it is not obvious from the documentation which it should be.
>
> If which data goes into which of the matrix dimensions is not important, is
> a way to specify which is which, so that both layout can be used (at the
> user's discretion)?
>
> If the layout cannot be decided by the user, it should probably stand out
> somewhere in the documentation.
In fact, I have always seen Jacobians using this layout, so from my
point of view it was standard. I am conforted in this view by
<http://mathworld.wolfram.com/Jacobian.html>.
So I would prefer to see improved documentation rather than providing a
non-standard layout. I think you have already done this doc improvement
(I am trying to read all the mails that have arrived during my 2 days
unconnected ...)
best regards,
Luc
>
>
> Best regards,
> Gilles
>
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Re: [Math] Jacobian dimensions in "AbstractLeastSquaresOptimizer"
Posted by Luc Maisonobe <Lu...@free.fr>.
Le 02/09/2011 00:29, Gilles Sadowski a écrit :
> Hello Luc.
>
>>> [...]
>>
>> In fact, I have always seen Jacobians using this layout, so from my
>> point of view it was standard. I am conforted in this view by
>> <http://mathworld.wolfram.com/Jacobian.html>.
>
> That goes without saying, but it does not harm to say it anyway. :-)
> [I just happened to pick the wrong layout because it looked more natural for
> looping...]
>
>> So I would prefer to see improved documentation rather than
>> providing a non-standard layout. I think you have already done this
>> doc improvement (I am trying to read all the mails that have arrived
>> during my 2 days unconnected ...)
>
> Yes, I've added a note in the "AbstractLeastSquares" class comment.
> Please check that it is clear enough.
Yes, it is clear.
Thanks,
Luc
>
>
> Best,
> Gilles
>
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Re: [Math] Jacobian dimensions in "AbstractLeastSquaresOptimizer"
Posted by Gilles Sadowski <gi...@harfang.homelinux.org>.
Hello Luc.
> > [...]
>
> In fact, I have always seen Jacobians using this layout, so from my
> point of view it was standard. I am conforted in this view by
> <http://mathworld.wolfram.com/Jacobian.html>.
That goes without saying, but it does not harm to say it anyway. :-)
[I just happened to pick the wrong layout because it looked more natural for
looping...]
> So I would prefer to see improved documentation rather than
> providing a non-standard layout. I think you have already done this
> doc improvement (I am trying to read all the mails that have arrived
> during my 2 days unconnected ...)
Yes, I've added a note in the "AbstractLeastSquares" class comment.
Please check that it is clear enough.
Best,
Gilles
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