Sparse matrices / arrays in Java

Posted by DanM on Stack Overflow See other posts from Stack Overflow or by DanM
Published on 2008-12-23T21:55:14Z Indexed on 2010/03/22 21:41 UTC
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sparse-array

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I'm working on a project, written in Java, which requires that I build a very large 2-D sparse array. Very sparse, if that makes a difference. Anyway: the most crucial aspect for this application is efficency in terms of time (assume loads of memory, though not nearly so unlimited as to allow me to use a standard 2-D array -- the key range is in the billions in both dimensions).

Out of the kajillion cells in the array, there will be several hundred thousand cells which contain an object. I need to be able to modify cell contents VERY quickly.

Anyway: Does anyone know a particularly good library for this purpose? It would have to be Berkeley, LGPL or similar license (no GPL, as the product can't be entirely open-sourced). Or if there's just a very simple way to make a homebrew sparse array object, that'd be fine too.

I'm considering MTJ, but haven't heard any opinions on its quality.

Thanks!! -Dan

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