I can reproduce this issue.
Furthermore, while trying to understand it, I found a workaround.
A ([:*/&:>>.&#{.!.1&.>;)&$B
|domain error
A ([:*/&:>>.&#{.!.1&.>;)&{{y}}&$B
6 6
The success of this workaround suggests an issue with special code.
Thanks,
--
Raul
On Fri, Oct 1, 2021 at 3:23 AM Jan-Pieter Jacobs
<[email protected]> wrote:
>
> Hi,
> Yesterday I was playing with the Kronecker product, trying to extend it to
> arbitrary dimensions (not that I really needed, but it seemed fun). It
> works on this J:
> JVERSION
> Engine: j902/j32/android
> Release-a: commercial/2020-12-24T11:35:03
> Library: 9.02.08
> Platform: Android 32 (armeabi-v7a)
> Installer: unknown
> InstallPath: /mnt/sdcard/Android/data/com.jsoftware.j.android/files
> Contact: www.jsoftware.com
>
> But not on beta-r, nor beta-s on windows 64, avx2.
>
> The definition is as follows (based on
> https://wiki.jsoftware.com/wiki/Essays/Kronecker_Product):
>
> kp=: cs ($,) dp |: *"0 _
> NB. cs calculates the eventual size of pairwise joining axes
> cs=: ([: */&:> >.&# {.!.1&.> ;)&$
> NB. dp calculates the axis shuffle needed to interleave corresponding axes
> of x and y
> dp=: (+ {. [: ,@|:@i. 2 , >.)&(#@$)
>
> A=: =i. 3 NB. identity, shape 3 3
> B=: >:i. 2 2 NB. shape 2 2
> AA=: 0 13 26 e.~i. 3 3 NB. shape 3 3 3
>
> 'A kp B' and 'AA kp B' fail because 'A cs B' and 'AA cs B' throw a domain
> error in J903-beta-r/s I don't understand, but do work in J902. Dissect
> mentions an inconsistency, but eventually shows the right result.
>
> however, removing &$ from cs and feeding in shapes directly does work.
>
> 3 3 3 ([: */&:> >.&# {.!.1&.> ;) 2 2
> 6 6 3
>
> Am I missing something or is this an interpreter bug?
>
> Any comments on the Kronecker product as such, does it make sense? The 2x2
> case is at least consistent with the definitions in the essay.
> If it is sound, I'd add it to the Essay.
>
> Best regards,
> Jan-Pieter.
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