Here's an example of x10 speed difference:
ts=: 6!:2 , 7!:[EMAIL PROTECTED]
A=. 1e6 [EMAIL PROTECTED] 0
s;s{A [ s=. 3{.\:A
+--------------------+------------+
|736817 218905 249629|1 1 0.999999|
+--------------------+------------+
3 maxima A
+--------------------+------------+
|736817 218905 249629|1 1 0.999999|
+--------------------+------------+
ts 's;s{A [ s=. 3{./:A'
0.477354 8.91398e6
ts '3 maxima A'
0.0402036 8.39219e6
NB. =========================================================
maxima=: 4 : 0
sb=. <./ y
rv=. ''
ri=. ''
for_i. i.x do.
mv=. >./y
mi=. y i. mv
y=. sb mi}y
rv=. rv,mv
ri=. ri,mi
end.
ri;rv
)
NB. =========================================================
It catches up at 40 for 1,000,000.
ts '40 maxima A'
0.46322 8.39322e6
k time
2 0.0317765
4 0.0536817
8 0.105835
16 0.194492
32 0.372339
64 0.724887
128 1.42764
k % time
62.9396 74.5133 75.5894 82.2656 85.9432 88.2896 89.6585
i.e. maxima is linear WRT k. Where /: would be practically const.
--- Roger Hui <[EMAIL PROTECTED]> wrote:
> If you just want the largest value (and its position) then
> it can be done conveniently without sorting or grading.
> If you want the largest k values where k>1 then
> the most convenient way is to grade, along the lines
> that Raul Miller has shown.
>
> Why do you want to avoid sorting/grading? In J, for vectors
> of many datatypes, including the integer and floating point
> datatypes, sorting and grading takes linear time.
>
>
>
> ----- Original Message -----
> From: Nick Kostirya <[EMAIL PROTECTED]>
> Date: Thursday, March 20, 2008 2:25
> Subject: [Jprogramming] Biggest values from list
> To: [email protected]
>
> > Hello, All
> >
> > Can you please provide me with the most optimal way of picking
> > out a
> > given number of elements with the biggest values from a huge list?
> >
> > The values and the elements' positions in a list are a matter of
> > interest.
> >
> > Can we manage this without sorting?
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
____________________________________________________________________________________
Never miss a thing. Make Yahoo your home page.
http://www.yahoo.com/r/hs
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
