Re: [Chicken-users] About peformance of user defined procedures

[Kon Lovett]

On Jul 30, 2011, at 4:43 PM, Pedro Henrique Antunes de Oliveira wrote:

> Hey.
> 
> I have a file map.scm, which contais this code:
> 
> (define (mymap1 op ls)
>  (let loop ((ls ls) (acc '()))
>    (if (null? ls)
>        (reverse acc)
>        (loop (cdr ls) (cons (op (car ls)) acc)))))
> 
> (define (mymap2 op ls)
>  (let loop ((ls ls))
>    (if (null? ls)
>        '()
>        (cons (op (car ls)) (loop (cdr ls))))))
> 
> (define (mymap3 op ls)
>  (if (null? ls)
>      '()
>      (cons (op (car ls)) (mymap3 op (cdr ls)))))
> 
> (define ls (let loop ((i 0)) (if (= i 1000000) '() (cons i (loop (add1 i))))))
> 
> And another four files, f1.scm, f2.scm, f3.scm, f4.scm.
> 
> f1.scm
> (include "map.scm")
> (map add1 ls)
> 
> f2.scm
> (include "map.scm")
> (mymap1 add1 ls)
> 
> f3.scm
> (include "map.scm")
> (mymap2 add1 ls)
> 
> f4.scm
> (include "map.scm")
> (mymap3 add1 ls)
> 
> Compiling all four f[1-4].scm files, with csc -O3, I got those results:
> 
> f1 took 0.95secs (average)
> f2 took 1.65secs (average)
> f3 took 1.35secs (average)
> f4 took 1.35secs (average)
> 
> I understand why f4 and f3 are pretty much the same thing, but what
> differs from mine to the built in map that makes the built in so
> faster (2-3x faster)?

I think map is one of the procedures "open-coded" by the compiler.

> 
> Interpreted languages have this characteristic that built in
> procedures tend to be much faster, but this all is compiled. I suppose
> it is possible to make procedures, in chicken/scheme that are as fast
> as the built in one. Right?

See compiler macros.

> 
> Note: compiling with -O5 instead of -O3 made the programs 0.1secs "shorter".
> Note2: this is not about map specifically (I've been looking at some
> procedures that I have that look somewhat to some built in ones, but
> are much slower)
> 
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