Re: [Chicken-users] compile time wanderings

[Felix Winkelmann]

Cs. Henk wrote:
> Hi!
>
> I tested the compilation of the following kind of code:
>
> (define (f0) 0)
> (define (f1) (+ 1 (f0)) )
> (define (f2) (+ 1 (f1)) )
> (define (f3) (+ 1 (f2)) )
> (define (f4) (+ 1 (f3)) )
> (define (f5) (+ 1 (f4)) )
> ...
> (display (f1000)) (newline)
>
> with different values in place of 1000.
>
> First I tried to do it with 10000, I got bored after some hours, so I
> stopped the compilation.
>
> Then trying it with 1000, 2000, and 3000, I had the feeling that compile
> time grows exponentially (for 1000, the code compiled in cca. 40 sec
> time, for 2000, it needed 2 minutes, for 3000, it took cca. 5 and a half
> minutes). 

Yes, especially the closure-conversion phase is rather expensive and
takes a lot of time. You can run chicken with the -debug b option
to see how long each compilation phase takes.

> And then I re-tried the above with 10000 as follows: broke up the code
> to 1000-line chunks, compiled them separately, linked the object files.
> This procedure, of course, took ten times longer than the compilation
> time with 1000.
>
> Now I wonder what property of chichken causes that compilation time
> grows exponentially related to code size, and that is there a way to
> make it behave similary during the compilation of one big file 
> to the case when several small files are compiled and linked... ?

Jonah Beckford is working on a new feature that allows splitting a compiled
Scheme file into several .c files that can be compiled separately. But this
is mainly intended to reduce C compile times.

There lurk a few suboptimal algorithms in the compiler, admittedly. I will
try to address this, but don't hold your breath... ;-)


cheers,
felix