On Sun, 2012-08-19 at 00:49 +0200, Ludovic Courtès wrote: > Hi, > > nalaginrut <nalagin...@gmail.com> skribis: > > > I think our quasiquote is too slow, here's an algorithm to test it. > > 1. quasiquote version: > > https://gist.github.com/3148984 > > 2. use list append to instead > > https://gist.github.com/3148977 > > > > The input value is 6000. > > v1 cost ~50s for me. > > v2 ~16s. > > I’m not sure what you’re measuring here. > > I commented out the I/O, and tried this variant with len = 20000: > > --8<---------------cut here---------------start------------->8--- > (use-modules (ice-9 time)) > > (define (one len) > (let* ((ll ((@ (srfi srfi-1) iota) len 1)) (m (1- (/ len 2)))) > (display len)(newline) > (time > (let lp((a (list-head ll (1+ m))) (b (list-tail ll (1+ m))) (n 1)) > (and (< n len) > (lp (append (list 1 (car b)) (cdr a)) (append (cdr b) (list > (list-ref a m))) (1+ n))))))) > > (define (two len) > (let* ((ll ((@ (srfi srfi-1) iota) len 1)) (m (1- (/ len 2)))) > (display len)(newline) > (time > (let lp((a (list-head ll (1+ m))) (b (list-tail ll (1+ m))) (n 1)) > (and (< n len) > (lp `(1 ,(car b) ,@(cdr a)) `(,@(cdr b) ,(list-ref a m)) (1+ > n))))))) > --8<---------------cut here---------------end--------------->8--- > > Both take ~7.12 seconds on my laptop. >
Yes, Ludo, I realized that my measurement was little different: -----------code--------- echo 6000 | ./v1.scm 1>/dev/null -----------end---------- So I believe the delayed time caused by I/O. But I can't reproduce the measure data I provided now(both stable-2.0/wip-rtl), since it's been a while, I guess the later Guile got some promotion? And I can't remember the commit version I've tried (hmm...I should provide it). > In terms of code, the only difference is that, in ‘two’, the first > argument of the recursive call is optimized as: > > (cons 1 (cons (car b) (cdr a))) > > whereas ‘one’ uses ‘append’. In this case, there’s no real difference > between the two in terms of performance. > Thanks for explain! I was always suspect that the difference in code level between append and quasiquote, now I learned something. > Can you please be more precise as to what felt “slow” for you, and > exactly how you measured execution times? > > Thanks, > Ludo’.
