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Re: register-compiled-module performance

From: Matt Welland
Subject: Re: register-compiled-module performance
Date: Sat, 11 Jan 2020 18:55:20 -0700

On Sat, Jan 11, 2020 at 8:47 AM megane <address@hidden> wrote:

Matt Welland <address@hidden> writes:

> With Chicken 4 I'm seeing a pretty high impact on startup time from
> (declare (uses foo.import)). I think that will be less of a problem when I
> switch from using * for my export lists to only the procedures that need to
> be exported. However I was very surprised to see readline in the top three
> when I ran a profile. I'm thinking somehow I've created a genuine problem
> but I've no idea what to look for.
> Suggestions?

I'd guess this is from the O(n^2) behaviour of merge-se in modules.scm.
This has been fixed in C5.

Ok, that is good to know. I'll not worry about startup time for now and will put the energy into getting to chicken 5. Thanks.
Here's a version for C4 that I used to use:

(define (merge-se . ses*) ; later occurrences take precedence to earlier ones
  (let ([table (make-hash-table)]
        [rses (reverse ses*)])
    (let loop ([ses (cdr rses)]
               [last-se #f]
               [se2 (car rses)])
       [(null? ses) se2]
       [(eq? last-se (car ses))
        (loop (cdr ses) last-se se2)]
       [(null? (car ses))
        (loop (cdr ses) last-se se2)]
       [(not last-se)
        (for-each (lambda (e) (hash-table-set! table (car e) #t)) se2)
        (loop ses se2 se2)]
        (let lp ([se (car ses)]
                 [se2 se2])
           [(null? se) (loop (cdr ses) (car ses) se2)]
           [(hash-table-exists? table (caar se))
            (lp (cdr se) se2)]
            (hash-table-set! table (caar se) #t)
            (lp (cdr se) (cons (car se) se2))]))]))))
> Note - migration is a work in progress but we are not quite at a point
> where I can test this in Chicken 5.
> procedure                                                          calls
>  seconds  average  percent
> ---------------------------------------------------------------------------------------------------
> <syntax>                                                              29
>  1.880    0.064   12.384
> megamod.import.scm:71: ##sys#register-compiled-module                  1
>  1.660    1.660   10.935
> readline.scm:74: ##sys#register-compiled-module                        1
>  1.580    1.580   10.408
> runsmod.import.scm:43: ##sys#register-compiled-module                  1
>  1.350    1.350    8.893

Complexity is your enemy. Any fool can make something complicated.
It is hard to keep things simple. - Richard Branson.

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