On 12/31/2015 11:10 AM, Gilles wrote:
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.
RealMatrixFormat.parse() first creates a double[][] and then it drops it into
the Matrix wrapper it thinks is best, per MatrixUtils. By leaving out the last
step the caller can either use MatrixUtils (Or hopefully MatrixFactory) to
perform the next step. Or maybe there is no next step. Perhaps just having a
double[][] is fine.
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.
I agree in general. I'm sticking all the 'Real' (Excluding Field) classes in
one module (Vector and Matrix). AbstractRealMatrix uses RealMatrixFormat, so
it's tightly coupled ATM and it seems like it belongs with the real Vector and
Matrix classes so...
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).
That was what I was seeing as well. Once matrix rows reach 100K - 10 million
performance goes up between 2X and 5X, but I did not really see any difference
for (multiplication only) in performance for small data sets. So I'm assuming,
like Luc indicated, that the Array2DRowRealMatrix is only better when
attempting to reuse the underlying double[][] matrix a lot...
Cheers,
Ole
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