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Date: Thu, 31 Dec 2015 18:10:54 +0100
From: Gilles <gilles@harfang.homelinux.org>
To: <dev@commons.apache.org>
Subject: Re: [math] RealMatrixFormat.parse()
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On Wed, 30 Dec 2015 21:33:56 -0600, Ole Ersoy wrote:
> Hi,
>
> In RealMatrixFormat.parse() MatrixUtils makes the decision on what
> type of RealMatrix instance to return.

Ideally, this is correct as the actual type is an "implementation 
detail".

> Flexibility is gained if it
> just returns double[][] letting the caller decide what type of
> RealMatrix instance to create.

That could become a problem e.g. for sparse matrices where the 
persistent
format and the instance type could be optimized for space, but a 
"double[][]"
cannot be.

> It's also better for modularity, as is
> reduces RealMatrixFormat imports (The MatrixUtils supports Field
> matrices as well, and I'm attempting to separate real and field
> matrices into two difference modules).

For modularity, IO should not be in the same module as the core
algorithms.

> Also just curious if Array2DRowRealMatrix is worth keeping?  It seems
> like the performance of BlockRealMatrix might be just as good or
> better regardless of matrix size ... although my testing is limited.

I recall having performed a benchmark years ago and IIRC, the
"BlockRealMatrix" started to be more only for very large matrix size
(although I don't remember which).

Regards,
Gilles


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