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From Ted Dunning <>
Subject Re: [MATH] Re: Pivoting QR Decomposition: Take Two!
Date Thu, 06 Oct 2011 16:08:14 GMT
Actually, you can easily get all the information at least in degenerate

The two cases are:

    - getPivot() ... the identity permutation can be returned

    - getRank() ... it is reasonable to throw an exception stating that rank
is not available (UnsupportedOperationException, in particular).  This is
*exactly* analogous to the way that many iterators do not allow remove() to
be called.

On Thu, Oct 6, 2011 at 3:21 AM, Gilles Sadowski <> wrote:

> IIUC, there are things you can query from a "PivotingQRDecomposition" that
> you cannot from the "FastQRDecomposition", then when you get the interface
> "QRDecomposition", you've lost these additional features. And if you impose
> that the interface contains them, then if you request the "fast"
> implementation, and then query the "pivoting" features, what happens?

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