[Fwd: Re: improved Matrix.times()]

[Ron Boisvert <boisvert@nist.gov>]

Sender: Anders Peterson <anders_peterson@optimatika.se>
Subject: Re: improved Matrix.times()


I don't think all your suggested changes are good. The only really 
unfortunate things I see in the jama code is the 'Arowi' and 's' 
declarations inside the loops. It would be much better to declare those 
temporary variables once before the looping begins and then simply 
assign 'Arowi = A[i];' and 's = 0;' inside the loops.

Not sure having a local copy (or not) of the left matrix' row makes much 
difference, but I'm sure the local copy of the right matrix' column and 
the 's' makes a speed difference.

/Anders
-----------------------------
http://ojalgo.org/


Marcell Missura wrote:
> After trying to multiply two huge matrices and running out of heap memory
> I suggest to juice up the times(Matrix) method of the Matrix class with
> the following few lines to avoid creating a massive amount of garbage on
> the heap that needs to be collected.
>
> public Matrix times(Matrix B)
> {
>        if (B.m != n)
>                throw new IllegalArgumentException("Matrix inner
> dimensions must agree.");
>
>        Matrix C = new Matrix(m, B.n);
>
>        for (int i = 0; i < m; i++)
>                for (int j = 0; j < B.n; j++)
>                        for (int k = 0; k < n; k++)
>                                C.A[i][j] += A[i][k] * B.A[k][j];
>
>        return C;
> }
>
>
>
>
>
>
>