Makes perfect sense, noting that because dyadic A. has left-rank 0, it is
called !10 times…
On Tue, May 26, 2020, 09:06 Raul Miller <rauldmil...@gmail.com> wrote:
> There's an opportunity here for improving idioms like (A.&i.~ !)
>
> But, A. is already a lot faster than perm in some other contexts:
>
> !10
> 3.6288e6
> 3e6 A. i.10
> 8 2 4 1 7 0 3 5 6 9
> 3e6 { perm 10
> 8 2 4 1 7 0 3 5 6 9
> timespacex '3e6 A. i.10'
> 4e_6 1856
> timespacex '3e6 { perm 10'
> 0.198427 6.3754e8
>
> Makes sense?
>
> --
> Raul
>
> On Tue, May 26, 2020 at 2:51 AM Jan-Pieter Jacobs
> <janpieter.jac...@gmail.com> wrote:
> >
> > Yes, I just figured it out the same definition.
> >
> > However, I was very surprised to see perm massively outperforms tap:
> >
> > timespacex 'a=: perm 10'
> > 0.3946 3.18771e8
> > timespacex 'b=: (A.&:i.~ !) 10'
> > 2.74118 5.62038e8
> > a-:b
> > 1
> >
> > JVERSION
> > Engine: j901/j32/android
> > Release-e: commercial/2020-02-09T15:23:16
> > Library: 9.01.24
> > J Android: 1.4.08/7.1.2/25
> > Platform: Android 32 (armeabi-v7a)
> > Installer: unknown
> > InstallPath:
> /storage/emulated/0/Android/data/com.jsoftware.j.android/files
> > Contact: www.jsoftware.com
> >
> >
> > Perhaps an opportunity for performance improvement in dyadic A. ?
> >
> > Best regards,
> >
> > Jan-Pieter
> >
> > On Mon, May 25, 2020, 22:59 'Mike Day' via Programming <
> > programm...@jsoftware.com> wrote:
> >
> > > If I can’t remember the idiom, I look for “tap.” My favourite form is
> > > tap =: A.&i.~ !
> > >
> > > (perm-: tap)3. NB. Same results.....
> > > 1
> > >
> > > Cheers,
> > >
> > > Mike
> > > Sent from my iPad
> > >
> > > > On 25 May 2020, at 21:44, Skip Cave <s...@caveconsulting.com> wrote:
> > > >
> > > > perm
> > > >
> > > > 3 : 0
> > > >
> > > > z=. i.1 0
> > > >
> > > > for. i.y do. z=. ,/ (0 ,. 1 + z) {"2 1 \:"1 = i. 1 + {: $z end.
> > > >
> > > > :
> > > >
> > > > ,/ ({~ perm@#)"1 x comb y
> > > >
> > > > )
> > > >
> > > >
> > > ----------------------------------------------------------------------
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> > >
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> ----------------------------------------------------------------------
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