Hi.

In interface "LeastSquaresProblem.Evaluation" (in package "o.a.c.m.fitting.leastsquares"), the argument to method "getCovariances(double)" defines the condition for an exception to be thrown when the product of the Jacobian matrix with its transpose is deemed singular.

The Javadoc does not specify the meaning of the singularity "threshold". If I'm not mistaken, the value for the threshold should be different whether we consider the product above, or the Jacobian matrix itself. Also, the meaning of the threshold seems
tied to the QR decomposition.

I wonder whether we should not select a "more objective" criterion to determine when
the Jacobian should be considered singular.
Is it possible to assert that below a certain threshold, the inversion is bound to
produce garbage and thus set a hard-coded default?


Best regards,
Gilles


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