[plt-scheme] Hash Table implementation

Weird... I get this too.  By the way, if you drop the 'equal symbol,
and use fixnums instead of fractions, the strange behavior goes away.
So it's a bug that depends on the equality-checking...

Keith F.

On 8/3/07, David Einstein <deinst at gmail.com> wrote:
> Inspired by Jens and Grant, I decided to try my hand at some of the Project
> Euler problems using PLT scheme, to see what it was capable of.  It has
> proven itself capable on the few problems that I have completed so far, but
> I just ran into what appears to be a bug of sorts.  It appears that the
> hash-table implementation does not expand as more keys are added, and so if
> the table reaches a certain size things slow down dramatically.  For example
>
> (require (lib "42.ss" "srfi"))
>
> (define (randfrac n)
>   (/ (+ 1 (random n)) (+ 1 (random n))))
>
> (define ht (make-hash-table 'equal))
> (time (do-ec (: a 1 1000) (hash-table-put! ht (randfrac 1000) #t)))
> (time (do-ec (: a 1 10000) (hash-table-put! ht (randfrac 1000) #t)))
> (time (do-ec (: a 1 100000) (hash-table-put! ht (randfrac 1000) #t)))
>
> results in
>
> Welcome to DrScheme, version 370 [3m].
> Language: Graphical (MrEd, includes MzScheme); memory limit: 1024 megabytes.
> cpu time: 0 real time: 0 gc time: 0
> cpu time: 125 real time: 125 gc time: 0
> cpu time: 13047 real time: 13047 gc time: 0
> >
>
> _________________________________________________
>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
>