What I did was translate your
C_ijlmnop = sum_k A_ijkl * B_mknop
in J-terms. If that's not what you want, then your specs are imprecise.
Perhaps what you want to do (with thanks to Lochbaum), is
(('ijkl i. ijlk')|: A_ijkl ) (+/ . *) ('mknop i. kmnop')|: B_mknop
which is what Rich calculated.
This cannot be derived (in an easy way) from the outer product A_ijkl * B_mknop.
I would love to know how you would specify sum_k A_ijkl * B_mknop
R.E. Boss
> -----Oorspronkelijk bericht-----
> Van: Programming <[email protected]>
> Namens Rudolf Sykora
> Verzonden: vrijdag 7 februari 2020 15:43
> Aan: [email protected]
> Onderwerp: Re: [Jprogramming] multiply two multidimensional matrices
>
>
> R.E. Boss <[email protected]> writes:
>
> > a =. i. 2 3 4 5
> > b =. i. 2 4 3 5 6
> > $a *"0 _ b
> > 2 3 4 5 2 4 3 5 6
> > $+/"6 +/"4 a *"0 _ b
> > 2 3 5 2 3 5 6
>
> This is an interesting take on the subject.
>
>
> If I understand, the first part does an outer product, P,
>
> P_ijklmnopq = A_ijkl * B_mnopq .
>
> And I believe it does it right.
>
>
> However, what I now want to do is
>
> C_ijlmopq = sum_k P_ijklmkopq
>
> while, it seems to me, you do something different, something like
>
> D_ijlmnpq = sum_kn P_ijklmnopq,
>
> which is not what is wanted.
>
> In any case, the result of yours and of Henry Rich's, although having the same
> shape, differ. At this moment I think the latter is the right one, but I am
> not
> quite sure, yet.
>
>
> Thanks for trying!
> Ruda
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