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From "Gilles (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-717) A varied class of Array2DRowRealMatrix is needed to contain float type instead of double.
Date Wed, 14 Dec 2011 13:21:30 GMT

    [ https://issues.apache.org/jira/browse/MATH-717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13169327#comment-13169327
] 

Gilles commented on MATH-717:
-----------------------------

If I'm not mistaken, that would mean a complete copy/paste of the code of the class (and its
parents), replacing "double" by "float". This is easy to do once; not nearly as easy to maintain!
I don't think that a feature aimed only at testing "small enough" problems is a quite good
reason to push in that direction. What would you be testing anyway, since for the "real" problems,
you'd have to switch to S├ębastien's linear operator framework?

Furthermore, the matrix API has been under discussion, and if we are going to modify it, it
should rather be done before adding more implementations.
Another thing to be aware is that if the "float" implementation exists, users might start
to ask for other classes in the "linear" package to be converted (e.g. the "...Decomposition"
classes).
Further discussions (about design issues) should probably be brought over to the "dev" ML.

If your limitation is the Java heap memory in a 32-bit system, I'd suggest going 64-bit and
buying more RAM.

                
> A varied class of Array2DRowRealMatrix is needed to contain float type instead of double.
> -----------------------------------------------------------------------------------------
>
>                 Key: MATH-717
>                 URL: https://issues.apache.org/jira/browse/MATH-717
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 2.2
>         Environment: All
>            Reporter: Dusan Ku
>              Labels: features
>
> The current implementation of Array2DRowRealMatrix takes only double type as its base
element value in the matrix.
> However, the memory size of double is bigger than float, the downside of which makes
the matrix dimension quite limited, compared to float type as its base element type. For small
sized problem, this does not make such a big difference, but for large problems, this limits
the usability of this library quite severely. In my case, I easily hit an error even after
I increase the memory option to 1G. This could have been much more enhanced just by using
'float[][]' instead of the current Array2DRowRealMatrix.
> Therefore, the solution I may suggest is to add another class similar to Array2DRowRealMatrix
containing float type for its matrix variable instead of double. Of course, a better way is
welcome as long as the needs can be fulfilled.

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