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? >>> >> ---------------------------------------------------------------------- >>> >> 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