That's cheatin', looking at the source! :-)
Further comments later.
On Wed, Mar 5, 2014 at 12:11 PM, Joe Bogner <joebog...@gmail.com> wrote:
> Yes, the grade is done regardless. Here's my reasoning: In the
> incumbent version, s is taken from the grade with from { which is
> slower than just resorting.
> It seems like the difference between sorting and selecting by indexes.
> I am surprised if that's the answer though because selecting by index
> should be fast since it's a contiguous array.
>
> jtifrom looks more complicated than jtsortc but I haven't been able to
> figure out how jtsortc works.
>
> On Wed, Mar 5, 2014 at 2:50 PM, Roger Hui <rogerhui.can...@gmail.com>
> wrote:
> > x=: a.{~ 1e7 ?@$ 256
> > timer=: 6!:2
> >
> > 10 timer 's=:x{~g=:/:x'
> > 0.136961
> > 10 timer 's=:/:~x [ g=:/:x'
> > 0.0765459
> >
> > 10 timer '/:~x'
> > 0.012887
> > 10 timer 'x{~g'
> > 0.065751
> > 10 timer '/:x'
> > 0.0606987
> >
> >
> >
> > On Wed, Mar 5, 2014 at 11:45 AM, Roger Hui <rogerhui.can...@gmail.com
> >wrote:
> >
> >> That's my alternative faster expression as well. But the more
> interesting
> >> question is, why is it faster? Since we do the grade in both cases, the
> >> comparison is between /:~x and g{x (or x{~g) with g pre-computed. The
> >> answer does not depend knowledge specific to J.
> >>
> >>
> >>
> >>
> >>
> >> On Wed, Mar 5, 2014 at 11:38 AM, Joe Bogner <joebog...@gmail.com>
> wrote:
> >>
> >>> Sorting and grading separately seems faster
> >>>
> >>> timer=: 6!:2
> >>> x=:(1e7 $ 26?26) { 'abcdefghijklmnopqrstuvwxyz'
> >>> NB. incumbent
> >>> timer 's=: x{~g=: /:x'
> >>> 0.0914002
> >>>
> >>> NB. alternate
> >>> timer 'S=: /:~x[G=: /:x'
> >>> 0.0668677
> >>>
> >>> s-:S
> >>> 1
> >>> G-:g
> >>> 1
> >>>
> >>>
> >>> I am speculating that sorting does it in place? which is faster than
> >>> the selection from the grade
> >>>
> >>>
> >>>
> >>> On Wed, Mar 5, 2014 at 2:02 PM, Raul Miller <rauldmil...@gmail.com>
> >>> wrote:
> >>> > Hmm...
> >>> >
> >>> > G=:a.i.S=:/:~x
> >>> > is faster.
> >>> >
> >>> > But while s-:S, g and G are different.
> >>> >
> >>> > So I'm drawing a blank here, on how to make the grade.
> >>> >
> >>> > Thanks,
> >>> >
> >>> > --
> >>> > Raul
> >>> >
> >>> >
> >>> >
> >>> > On Wed, Mar 5, 2014 at 1:52 PM, Roger Hui <rogerhui.can...@gmail.com
> >
> >>> wrote:
> >>> >
> >>> >> Suppose x is a long vector of characters and you need both its sort
> >>> and its
> >>> >> grade. Can you do it faster than s=: x{~g=: /:x ?
> >>> >>
> >>> >> Posed this way, the answer is of course yes. But how, and why is it
> >>> >> faster?
> >>> >>
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> >>> >>
> >>> >
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> >>>
> >>
> >>
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