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From Luc Maisonobe <Luc.Maison...@free.fr>
Subject Re: [math] RealMatrixImpl, DenseRealMatrix and MatrixUtils factory methods
Date Sat, 07 Feb 2009 21:12:42 GMT
Phil Steitz a écrit :
> I noticed a breakage in one of my apps that uses
> MatrixUtils#createRealMatrix(double[][], boolean).  This method seems to
> have been removed.  I guess this is because DenseRealMatrix can't
> support this.  I understand the value of DenseRealMatrix, but I still
> see value in the double[][]-backed RealMatrixImpl.  Any objections if I
> restore the method above, change the other factories to return
> RealMatrixImpl instances as before and add createDenseMatrix()
> methods?   I would also be OK with deprecating the createRealMatrix()
> methods and adding CreateXx methods for both versions.

I don't feel comfortable with this approach. The boolean parameter was
merely an optimization feature avoiding a copy. However, it implicitely
relied on one implementation only (RealMatrixImpl) and exposed an
internal array. As far as I understood, the factory methods in
MatrixUtils were used to hide the implementation. If they become
implementation-specific, I don't see the added value for factory methods
versus class constructors.

Nevertheless, my concerns are minor ones. Feel free to bring these
methods back if you consider there is a need for them.

In the same spirit, I am currently testing another block layout using
blocks size in a range rather than fixed size and recursive layout. This
is roughly an implementation based on Chatterjee, Lebeck, Praveen and
Thottethodi paper "Recursive Array Layouts and Fast Matrix
Multiplication" (http://www.cs.duke.edu/~alvy/papers/matrix-tpds.pdf).
If the performances are good, I will use this layout for DenseRealMatrix.

Luc

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