Is there a standard way to make random trationals? Linda
-----Original Message----- From: Programming [mailto:[email protected]] On Behalf Of Henry Rich Sent: Sunday, January 31, 2016 9:52 PM To: [email protected] Subject: Re: [Jprogramming] Joining lists When you throw in a floating-point conversion the fraction of time owing to copying arguments becomes smaller. Henry Rich On 1/31/2016 9:38 PM, Jose Mario Quintana wrote: > " > The observed ratio of measurements for the two operations, in both > space and time, is pretty close to (3%5) as we would expect from the above. > " > > It makes sense; yet, what I found interesting was that a measure of > overall (in)efficiency, the space*time, gain seems different for the two > samples: > > 1.68731e6 3.33377e6 % 664728 1.81216e6 > 2.53834651 1.83966648 > > > > On Sun, Jan 31, 2016 at 9:08 PM, Marshall Lochbaum > <[email protected]> > wrote: > >> It's not surprising at all if you know a little bit about how the >> verbs in question work. Dyad (,) creates a new array and copies its >> arguments into it. Thus computing (a,b,c) requires the steps: >> - Copy b and c into new array t1 (2e6 copy operations) >> - Copy a and t1 into new array t2 (3e6 copy operations). >> >> In contrast, dyad (;) is almost free, since it just creates an array >> of pointers to its arguments. Monad (;) computes the length of its >> result, allocates an array of that length, and then copies everything >> in, for a total of 3e6 copies. Provided we can't resize a to hold all >> the values (which would allow us to only copy b and c), this is >> optimal with J's array layout. >> >> The observed ratio of measurements for the two operations, in both >> space and time, is pretty close to (3%5) as we would expect from the above. >> >> Marshall >> >> On Sun, Jan 31, 2016 at 08:35:01PM -0500, Jose Mario Quintana wrote: >>> That is interesting, I was independently testing the same expression >>> ;A >> ; >>> B ; C vs A , B , C with different sample nouns and it seems >>> leaner and >>> meaner: >>> >>> st=. (, */&.:>@:(1 2&{))@:(] ; 7!:2@:] ; 6!:2) >>> >>> 'A B C'=. i.3 1000000 >>> >>> 111 st&>'A , B , C' ; ';A ; B ; C' >>> ┌──────────┬────────┬─────────┬─────────┐ >>> │A , B , C │50333184│0.0335228│1.68731e6│ >>> ├──────────┼────────┼─────────┼─────────┤ >>> │;A ; B ; C│33556608│0.0198092│664728 │ >>> └──────────┴────────┴─────────┴─────────┘ >>> >>> (A , B , C) -: i.3000000 >>> 1 >>> (;A ; B ; C) -: i.3000000 >>> 1 >>> >>> Using your sample nouns it is not as dominant but remains dominant >>> nevertheless: >>> >>> A=:?~1000000 >>> B=:0.1+?~1000000 >>> C=:?~1000000 >>> >>> 111 st&>'A , B , C' ; ';A ; B ; C' >>> ┌──────────┬────────┬─────────┬─────────┐ >>> │A , B , C │67110400│0.0496758│3.33377e6│ >>> ├──────────┼────────┼─────────┼─────────┤ >>> │;A ; B ; C│50333824│0.0360027│1.81216e6│ >>> └──────────┴────────┴─────────┴─────────┘ >>> >>> (A , B , C) -: (;A ; B ; C) >>> 1 >>> >>> >>> JVERSION >>> Installer: j602a_win.exe >>> Engine: j803/2014-10-19-11:11:11 >>> Library: 6.02.023 >>> >>> >>> >>> On Sun, Jan 31, 2016 at 7:05 PM, Raul Miller <[email protected]> >> wrote: >>>> Oops, I meant: >>>> >>>> timespacex ';a;b;c' >>>> 0.012332 5.03338e7 >>>> timespacex ';a;b;c' >>>> 0.011768 5.03338e7 >>>> (;a;b;c)-:a,b,c >>>> 1 >>>> >>>> Efficiency characteristics are the same, result (the most important >>>> part) is different. >>>> >>>> -- >>>> Raul >>>> >>>> On Sun, Jan 31, 2016 at 7:04 PM, Raul Miller >>>> <[email protected]> >>>> wrote: >>>>> If I define: >>>>> a=:?~1000000 >>>>> b=:0.1+?~1000000 >>>>> c=:?~1000000 >>>>> >>>>> I get: >>>>> timespacex 'a,b,c' >>>>> 0.016585 6.71104e7 >>>>> timespacex '>a;b;c' >>>>> 0.012863 5.0334e7 >>>>> timespacex '>a;b;c' >>>>> 0.011867 5.0334e7 >>>>> timespacex 'a,b,c' >>>>> 0.015703 6.71104e7 >>>>> >>>>> So it looks like >a;b;c is slightly more efficient than a,b,c, but >>>>> it's nowhere close to a factor of 2, so I think I'd ignore this >>>>> issue in most contexts. >>>>> >>>>> -- >>>>> Raul >>>>> >>>>> >>>>> On Sun, Jan 31, 2016 at 5:21 PM, Henry Rich <[email protected]> >>>> wrote: >>>>>> You have 3 large lists a, b, c (1000000 atoms each). You want to >> join >>>> them >>>>>> into one long list. What is the best way to do this? >>>>>> >>>>>> Henry Rich >>>>>> >> --------------------------------------------------------------------- >> - >>>>>> 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
