Are you running your timings comparison many times to make sure? I do (666
times). Alternatively, are the relative timings affected significantly by
the platform?
JVERSION
Installer: j602a_win.exe
Engine: j803/2014-10-19-11:11:11
Library: 6.02.023
666 st&> 'closest P' ; 'close2 P' ; 'nnf P'
┌─────────┬─────┬──────────┬────────┐
│closest P│23296│2.87491e_5│0.669738│
├─────────┼─────┼──────────┼────────┤
│close2 P │15104│4.55035e_5│0.687284│
├─────────┼─────┼──────────┼────────┤
│nnf P │10240│7.21532e_5│0.738849│
└─────────┴─────┴──────────┴────────┘
closest
#~ +/@(= <./@:(0 -.~ ,))@:|@:(-/~)@:(1 0j1 +/ .*~ ])
close2
#~ +/@(= ([: <./ 0 -.~ ,))@:([: | -/~)@:(j./"1)
nnf
{~ ((0 1 + ] , i.) (#~ (<: i.@:#)))@:([: ; (i.L:0 <./@:;))@:([: }.
<@:|@:({: - }:)\&:(j./"1))
On Thu, Sep 17, 2015 at 11:40 AM, 'Pascal Jasmin' via Programming <
[email protected]> wrote:
> A variation on your version with the same speed (actually slightly slower
> at 5th decimal) but smaller space
>
> close2 =: (#~ +/@(= [: <./ 0-.~,)@:([: | -/~)@:(j./"1))
>
>
>
>
>
> ----- Original Message -----
> From: Jose Mario Quintana <[email protected]>
> To: Programming forum <[email protected]>
> Cc:
> Sent: Thursday, September 17, 2015 10:23 AM
> Subject: Re: [Jprogramming] An adverb for a loopy algorithm
>
> Let us compare the two siblings, closest and nearest_neighbors together
> with its fixed version:
>
> nnf=. nearest_neighbors f. NB. Fixed version
>
> closest
> ] #~ +/@(= <./@:(0 -.~ ,))@:|@:(-/~)@:(1 0j1 +/ .*~ ])
> nnf
> {~ ((0 1 + ] , i.) (#~ (<: i.@:#)))@:([: ; (i.L:0 <./@:;))@:([: }.
> <@:|@:({: - }:)\&:(j./"1))
>
> 666 st&> 'closest P' ; 'nearest_neighbors P' ; 'nnf P'
> ┌───────────────────┬─────┬─────────────┬───────────┐
> │closest P │23296│3.27532288e_5│0.763019217│
> ├───────────────────┼─────┼─────────────┼───────────┤
> │nearest_neighbors P│10624│7.30659274e_5│0.776252412│
> ├───────────────────┼─────┼─────────────┼───────────┤
> │nnf P │10240│7.20269787e_5│0.737556262│
> └───────────────────┴─────┴─────────────┴───────────┘
>
> The nearest_neighbors verbs are leaner but closest runs twice as fast on my
> PC.
>
> They seem to produce the same results as long as there are no ties and
> no repetitions; otherwise there are issues:
>
> Q=. 0 ". every cutLF 0 : 0 NB. Tie
> _1 _1
> 0 1
> 1 0
> 1 1
> )
>
> R=. 0 ". every cutLF 0 : 0 NB. Repetition
> _1 _1
> _1 _1
> 0 0
> )
>
> (closest ; nearest_neighbors ; nnf) P
> ┌───────────────┬───────────────┬───────────────┐
> │6.42201 5.83321│6.42201 5.83321│6.42201 5.83321│
> │6.62593 6.08499│6.62593 6.08499│6.62593 6.08499│
> └───────────────┴───────────────┴───────────────┘
> (closest ; nearest_neighbors ; nnf) Q
> ┌───┬───┬───┐
> │0 1│0 1│0 1│
> │1 0│0 1│0 1│
> │1 1│ │ │
> │1 1│ │ │
> └───┴───┴───┘
> (closest ; nearest_neighbors ; nnf) R
> ┌─────┬─────┬─────┐
> │_1 _1│_1 _1│_1 _1│
> │_1 _1│_1 _1│_1 _1│
> │ 0 0│ │ │
> │ 0 0│ │ │
> └─────┴─────┴─────┘
>
>
> On Thu, Sep 17, 2015 at 1:38 AM, David Lambert <[email protected]>
> wrote:
>
> > If your task is actually 2D, consider complex numbers. This version
> > performs better on the sample data P=:p
> >
> > nearest_neighbors =: {~ convert_to_index@:identify_minimum@:separation
> >
> > separation =: [: }. <@:|@:({: - }:)\&:(j./"1)
> > identify_minimum =: [: ; (i.L:0 <./@:;)
> > convert_to_index=:(0 1 + ] , i.) (#~ (<: i.@:#))
> >
> > NB. examples by part
> > boxdraw_j_ 1
> >
> > separation 4{.P
> > +-------+---------------+-----------------------+
> > |3.71611|6.01287 6.83522|1.30641 4.14391 7.31405|
> > +-------+---------------+-----------------------+
> >
> > identify_minimum separation 4{.P
> > 1 2 0
> > convert_to_index identify_minimum separation 4{.P
> > 0 3
> > nearest_neighbors 4{.P
> > 6.42201 5.83321
> > 6.00479 7.07121
> > nearest_neighbors P
> > 6.42201 5.83321
> > 6.62593 6.08499
> >
> >
> > NB. time & space
> > close=: 3 :'y #~ +/@(= [: <./ 0-.~,)+/"1 *: -"1/~y' NB. RDM
> > flose=:nearest_neighbors f.
> > 999 timespacex"0 1 'close P',:'flose P'
> > 9.15946e_5 39680
> > 5.26036e_5 10240
> >
> > Date: Wed, 16 Sep 2015 19:49:56 +0000 (UTC)
> >> From: "'Pascal Jasmin' via Programming"<[email protected]>
> >> To: Programming Forum<[email protected]>
> >> Subject: [Jprogramming] An adverb for a loopy algorithm
> >> Message-ID:
> >> <[email protected]>
> >> Content-Type: text/plain; charset=UTF-8
> >>
> >> finding the 2 closest points in a set, has a loopy algorithm of "for
> each
> >> point, compare it with all of the points to its right"
> >>
> >> p =: 0 ". every cutLF 0 : 0
> >> 6.42201 5.83321
> >> 3.15448 4.06327
> >> 8.89456 0.352235
> >> 6.00479 7.07121
> >> 8.10462 9.19487
> >> 9.63448 4.00534
> >> 6.74378 0.791349
> >> 5.56034 9.27039
> >> 4.67282 8.45993
> >> 0.301042 9.4069
> >> 6.62593 6.08499
> >> 9.0307 2.37372
> >> 9.36324 1.80147
> >> 2.67396 1.62207
> >> 4.76667 1.94554
> >> 7.43839 6.05369
> >> )
> >>
> >
> > ----------------------------------------------------------------------
> > 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
>
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