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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
