hey hey - I posted my first answer before looking at the source and it didn't change my answer. Also, Roger has the source in his head and it wasn't ruled out of bounds.
On Wed, Mar 5, 2014 at 4:35 PM, Raul Miller <[email protected]> wrote: > My guess would be that it has something to do with cache coherence. > > Indexing is random access, sorting is more sequential in nature. > > But that's just a guess, because I did not cheat and look at the source or > anything (at least... not today). > > Thanks, > > -- > Raul > > > > On Wed, Mar 5, 2014 at 2:45 PM, Roger Hui <[email protected]> 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 <[email protected]> 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 <[email protected]> >> 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 <[email protected]> >> > 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? >> > >> ---------------------------------------------------------------------- >> > >> 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 >> > >> ---------------------------------------------------------------------- >> 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
