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List:       jakarta-commons-dev
Subject:    [Math] Jacobian dimensions in "AbstractLeastSquaresOptimizer"
From:       Gilles Sadowski <gilles () harfang ! homelinux ! org>
Date:       2011-08-31 16:09:32
Message-ID: 20110831160932.GO2590 () dusk ! harfang ! homelinux ! org
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Hello.

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.


Best regards,
Gilles

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