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From S├ębastien Brisard (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 Mon, 12 Dec 2011 07:14:31 GMT

    [ https://issues.apache.org/jira/browse/MATH-717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13167387#comment-13167387
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S├ębastien Brisard commented on MATH-717:
----------------------------------------

Hello,
this might be a silly question, but I was wondering about the nature of the data collected
in your matrix. Is it "experimental"? In my case, I often have huge matrices, but all coefficients
are generated procedurally, which calls for implementations where the matrix is *not* stored.
{{o.a.c.m.linear.RealLinearOperator}} was recently added to CM in order to fullfill this need,
together with iterative solvers. Not sure if that would be of any help to you; besides, this
is a very new feature, which would need to be extended.

As for me, I was initially adverse to your proposal, because {{floats}} are really ugly regarding
precision. I am now only half adverse, *as long as all internal calculations are carried out
in double precision*.
                
> 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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