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
> > >
> > > )
> > >
> > >
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> >
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
