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From "Ted Dunning" <>
Subject Re: [math] patch submitted for commons-math sparse matrix support
Date Mon, 01 Dec 2008 22:13:43 GMT

What do you think the trade-offs are between the representation that you
used and another one where you have a Map<int, SparseVector> that contains
rows or columns?

On Mon, Dec 1, 2008 at 1:40 PM, Sujit Pal <> wrote:

> Hello,
> I am a new, but fairly happy user of commons-math 1.2 and I have begun
> to use it in my code. I needed a sparse matrix implementation for some
> data analysis work I was doing, and unfortunately the code with
> RealMatrixImpl was coming back with an OOME. So I built a
> SparseRealMatrixImpl as a subclass of RealMatrixImpl, which uses a
> Map<Point,Double> as its backing store, storing only the non-zero
> entries. I would like to contribute this implementation back to the
> commons-math project.
> I have opened a JIRA enhancement request MATH-230 with a patch against
> the 2.0 branch. Patch and detailed description of the changes are
> available here.
> I have also had to make some changes to RealMatrixImpl and
> LUDecompositionImpl, mainly replacing the data[][] references with
> RealMatrix.getEntry(i,j) calls to insulate the backing store from being
> accessed directly by calling code, and thus making it possible for
> subclasses to provide their own internal backing stores.
> Would appreciate if you folks can take a look and let me know if it is
> feasible to add this into the 2.0 release. That way I can continue using
> commons-math future versions without having to patch it after every
> upgrade.
> I noticed that there has been some previous discussion about sparse
> matrix support here:
> so I sent a personal email to John Iacona asking him about about the
> code he speaks of here. But he is working on other things, and doesn't
> know when he will be able to check in his sparse matrix support changes.
> His approach is a little  different from mine (he has a SparseMatrix
> interface, which is implemented by a SparseMatrixImpl). I considered
> that approach initially, but came to the conclusion that it would mean
> quite a bit of code duplication, which I wanted to avoid as far as
> possible.
> Thanks
> -sujit
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Ted Dunning, CTO
4600 Bohannon Drive, Suite 220
Menlo Park, CA 94025
650-324-0110, ext. 738
858-414-0013 (m)

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