There's a variety of fibonacci implementations at http://www.jsoftware.com/jwiki/Essays/Fibonacci%20Sequence
I haven't looked at their timings, but you might find something interesting there. Good luck, -- Raul On Tue, Sep 1, 2015 at 8:32 PM, Jon Hough <jgho...@outlook.com> wrote: > In this talk https://www.youtube.com/watch?v=apBWkBDVlow > the presenter attempts to show Haskell hasn't sacrificed speed for > expressiveness by comparing a Java Fibonacci calculator to his Haskell > one.(skip to the 18:00 mark).Essentially, to calculate the 475000th Fibonacci > number, it took his Java program ~8 seconds, while the very terse Haskell > program took ~6 seconds. > So I tried to do the same in J. My first attempt, used a tacit, memoized verb > fib1 =:1:`(($:@:<:) + ($:@:-&2))@.(2&<)M. > > > However, this gives a stack error for large numbers (~100000). So I decided > to make an imperative verb, > > > fib2 =: 3 : 0 x1 =. x:1 x2 =. x:1 c =. 0 while. c < y do. tmp =. x1 x1 =. x2 > x2 =. tmp + x1 c=.c+1 end. x2 > > > > > > > > > > > > > ) > > > This gets there, I can calculate the 475000th Fibonacci number, but > > > timespacex 'fib2 475000' > > > > > 36.183 1.31558e6 > > > It takes 36 seconds (of course, my hardware is different to that in the > presentation, but still...). > > > Is there a speedier way to do this in J? Preferably a tacit one liner would > also be good. > > > Thanks, > Jon > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
