> `first` and `rest` need to check if the input is a list. Why is that?
On Fri, Jul 28, 2017 at 1:09 PM, Gustavo Massaccesi <gust...@oma.org.ar> wrote: > I was convinced that case-lambas were much slower. > > I made some tests, but I replaced first/rest with car/cdr beause it's > much faster. Also I repeated the call 1000 times. I got almost 1/2 > second of difference. > > opt cpu time: 12266 real time: 12264 gc time: 0 > acc cpu time: 11750 real time: 11745 gc time: 0 > opt cpu time: 12266 real time: 12272 gc time: 0 > acc cpu time: 11734 real time: 11737 gc time: 0 > opt cpu time: 12250 real time: 12264 gc time: 0 > acc cpu time: 11734 real time: 11749 gc time: 0 > > For comparison, if I divide the difference by 1000 I get 1/2 > millisecond of difference. So the difference between the version with > and without an optional argument is something like 94.5 vs 94.0 > (totally impossible to notice) instead of 281 vs 94 as I wrote in my > previous email. > > Gustavo > > > On Thu, Jul 27, 2017 at 10:36 PM, Robby Findler > <ro...@eecs.northwestern.edu> wrote: > > `first` and `rest` need to check if the input is a list (a linear-time > > but memoized test), whereas `car` and `cdr` check only if the inputs > > are `pair?`s, and match-define uses unsafe operations, doing the pair > > check only once. > > > > I see from raco demod that match-define does not generate very > > beautiful code, which leads me to this version (which is what I think > > match-define should have expanded into). It seems to be about 4x > > faster on my computer. > > > > #lang racket > > (require racket/unsafe/ops) > > (define (as) > > (build-list 1000000 (λ (n) (random 100)))) > > (define (bs) > > (build-list 1000000 (λ (n) (random 100)))) > > > > (define (z as bs [acc 0]) > > (cond > > [(or (null? as) (null? bs)) > > acc] > > [else > > (match-define (cons this-a more-as) > > as) > > (match-define (cons this-b more-bs) > > bs) > > (z more-as more-bs (+ acc (* this-a this-b)))])) > > > > (let ([as (as)] > > [bs (bs)]) > > (collect-garbage) > > (collect-garbage) > > (collect-garbage) > > (time (for ([i (in-range 10)]) > > (z as bs)))) > > > > (define (z2 as bs [acc 0]) > > (cond > > [(or (null? as) (null? bs)) > > acc] > > [else > > (define this-a (car as)) > > (define more-as (unsafe-cdr as)) > > (define this-b (car bs)) > > (define more-bs (unsafe-cdr bs)) > > (z2 more-as more-bs (+ acc (* this-a this-b)))])) > > > > (let ([as (as)] > > [bs (bs)]) > > (collect-garbage) > > (collect-garbage) > > (collect-garbage) > > (time (for ([i (in-range 10)]) > > (z2 as bs)))) > > > > > > > > Robby > > > > On Thu, Jul 27, 2017 at 8:27 PM, Philip McGrath > > <phi...@philipmcgrath.com> wrote: > >> `match-define` seems to be the real source of the speedup for me: > >> > >> #lang racket > >> > >> (define (as) > >> (build-list 1000000 (λ (n) (random 100)))) > >> (define (bs) > >> (build-list 1000000 (λ (n) (random 100)))) > >> > >> (define (f as bs [acc 0]) > >> (if (or (null? as) (null? bs)) > >> acc > >> (f (rest as) (rest bs) (+ acc (* (first as) (first bs)))))) > >> > >> (let ([as (as)] > >> [bs (bs)]) > >> (collect-garbage) > >> (collect-garbage) > >> (collect-garbage) > >> (time (f as bs))) > >> > >> > >> > >> (define (g as bs) > >> (let g ([as as] > >> [bs bs] > >> [acc 0]) > >> (cond > >> [(or (null? as) (null? bs)) > >> acc] > >> [else > >> (match-define (cons this-a more-as) > >> as) > >> (match-define (cons this-b more-bs) > >> bs) > >> (g more-as more-bs (+ acc (* this-a this-b)))]))) > >> > >> > >> (let ([as (as)] > >> [bs (bs)]) > >> (collect-garbage) > >> (collect-garbage) > >> (collect-garbage) > >> (time (g as bs))) > >> > >> (collect-garbage) > >> (collect-garbage) > >> (collect-garbage) > >> > >> (define (z as bs [acc 0]) > >> (cond > >> [(or (null? as) (null? bs)) > >> acc] > >> [else > >> (match-define (cons this-a more-as) > >> as) > >> (match-define (cons this-b more-bs) > >> bs) > >> (z more-as more-bs (+ acc (* this-a this-b)))])) > >> > >> (let ([as (as)] > >> [bs (bs)]) > >> (collect-garbage) > >> (collect-garbage) > >> (collect-garbage) > >> (time (z as bs))) > >> > >> ; timed at the command line > >> ;cpu time: 242 real time: 241 gc time: 0 > >> ;2452993452 > >> ;cpu time: 21 real time: 21 gc time: 0 > >> ;2450414634 > >> ;cpu time: 22 real time: 22 gc time: 0 > >> ;2450010495 > >> > >> -Philip > >> > >> On Thu, Jul 27, 2017 at 8:22 PM, Matthias Felleisen < > matth...@ccs.neu.edu> > >> wrote: > >>> > >>> > >>> On Jul 27, 2017, at 9:18 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > >>> > >>> I don't think optional arguments are all that slow. > >>> > >>> > >>> > >>> This isn’t just Matthew’s opinion. Vincent’s feature-specific profiler > >>> could not detect a significant impact of optional or keyword > arguments. (See > >>> Compiler Construction paper, London 2014 I think) > >>> > >>> -- > >>> You received this message because you are subscribed to the Google > Groups > >>> "Racket Users" group. > >>> To unsubscribe from this group and stop receiving emails from it, send > an > >>> email to racket-users+unsubscr...@googlegroups.com. > >>> For more options, visit https://groups.google.com/d/optout. > >> > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups > >> "Racket Users" group. > >> To unsubscribe from this group and stop receiving emails from it, send > an > >> email to racket-users+unsubscr...@googlegroups.com. > >> For more options, visit https://groups.google.com/d/optout. > > > > -- > > You received this message because you are subscribed to the Google > Groups "Racket Users" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to racket-users+unsubscr...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > -- *Daniel Prager* Agile/Lean Coaching, Innovation, and Leadership Profile: skillfire.co/dan Startups: youpatch.com <http://www.youpatch.com>, skillfire.co Twitter: @agilejitsu <https://twitter.com/agilejitsu> Blog: agile-jitsu.blogspot.com Linkedin: au.linkedin.com/in/danielaprager -- You received this message because you are subscribed to the Google Groups "Racket Users" group. 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