Observe this
20 ts 'c2 T'
0.017945407 26218880
c2 =: 3 : 0
a =: 2 | y
b =: 2 + 6 * y
c =: a } y ,: b
(_1 & (33 b.)) c
)
20 ts 'c2 T'
0.017914281 16780928
20 ts 'c1 T'
0.033379607 68163200
Using global defines, memory drops further to 1/4 of c1
R.E. Boss
(Add your info to http://www.jsoftware.com/jwiki/Community/Demographics )
> -----Original Message-----
> From: [email protected] [mailto:programming-
> [email protected]] On Behalf Of R.E. Boss
> Sent: donderdag 7 augustus 2014 12:14
> To: [email protected]
> Subject: Re: [Jprogramming] Memoizing (Project Euler problem 14)
>
> Also the memory is less than half
>
> ts 'c2 T'
> 0.025803916 26218880
> ts 'c1 T'
> 0.043909495 68163200
>
>
> R.E. Boss
>
> (Add your info to
> http://www.jsoftware.com/jwiki/Community/Demographics )
>
>
>
> > -----Original Message-----
> > From: [email protected]
> [mailto:programming-
> > [email protected]] On Behalf Of Roger Stokes
> > Sent: donderdag 7 augustus 2014 12:03
> > To: [email protected]
> > Subject: Re: [Jprogramming] Memoizing (Project Euler problem 14)
> >
> > Dear All,
> >
> > I've come across a puzzle
> > and would be glad if someone could explain it.
> >
> > In a few words, I have a variation of collatzv which is a one-liner
> > (c1 below) and the very same verb spread over several lines (c2
below).
> > The second is nearly twice as fast as the first. How come?
> >
> > The timings I get are
> >
> > collatzv T 0.0592513
> >
> > c1 T NB. one-liner 0.0582203
> >
> > c2 T NB. spread out 0.0352435
> >
> > where T is 2 + i. 1e6
> >
> > What follows is transcript of session producing these results.
> >
> > Starting with Roger Hui's original collatzv:
> >
> >
> > collatzv =: 3 : '<. (2|y)} 0 1 + 0.5 3 */y'
> >
> > NB. here is my one-liner, an experiment intended to stick to
> > NB. integer arithmetic throughout.
> >
> > c1 =: 3 : '(_1 & (33 b.)) (2 | y) } y ,: (2 + 6 * y)'
> >
> > NB. here is a spread-out version
> >
> > c2 =: 3 : 0
> > a =. 2 | y
> > b =. 2 + 6 * y
> > c =. a } y ,: b
> > (_1 & (33 b.)) c
> > )
> >
> > (collatzv -: c1) T =: 2 + i. 1e6
> > 1
> > (collatzv -: c2) T
> > 1
> >
> > NB. comparing timings:
> >
> > compare =: (; (6!:2)) @: > "0
> > compare 'collatzv T '; 'c1 T NB. one-liner '; 'c2 T NB. spread out'
> >
> > collatzv T 0.0587746
> >
> > c1 T NB. one-liner 0.0579726
> >
> > c2 T NB. spread out 0.0340378
> >
> >
> > NB. Do we get the same effect by spreading collatzv? No.
> >
> > collatzvs =: 3 : 0
> > a =. 0 1 + 0.5 3 */y
> > b =. 2|y
> > c =: b } a
> > <. c
> > )
> >
> > (collatzv -: collatzvs) T
> > 1
> >
> > compare 'collatzv T '; 'c1 T '; 'c2 T '; 'collatzvs T '
> >
> > collatzv T 0.0591852
> >
> > c1 T 0.0594112
> >
> > c2 T 0.034516
> >
> > collatzvs T 0.0597546
> >
> >
> > JVERSION
> > Engine: j701/2011-01-10/11:25
> > Library: 8.02.10
> > Qt IDE: 1.1.3/5.3.0
> > Platform: Win 64
> > Installer: J802 install
> > InstallPath: c:/users/homer/j64-802
> >
> >
> > ----------------------------------------------------------------------
> > For information about J forums see
> http://www.jsoftware.com/forums.htm
> ----------------------------------------------------------------------
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