Re: guile extension: python dictionary type

[Jay Glascoe <jglascoe@jay.giss.nasa.gov>]

> Is it preferable to hash tables in any particular way?
> 

I did some preliminary timing tests.  The python dictionaries seem to be
about 50% to 100% faster than guile's hash tables.  Guile's hash speed
depends a lot on the initial size of the vector.  The timing test is
below. "lines" is 581 lines from a postscript file.

(define do-test
  (lambda (lines number-times)
    (do ((i 1 (+ i 1)))
	((>= i number-times))
      (let ((mydict (make-vector 8)))
    ;;(let ((mydict (make-pydict)))
	(for-each (insert-entry mydict) lines)))))

(define insert-entry
  (lambda (mydict)
    (lambda (line)
      (let* ((len (string-length line))
	     (top (inexact->exact (/ len 10))))
	(let ((key (string->symbol (substring line 0 top)))
	      (value line))
	  (hash-set! mydict key value))))))
        ;;(pydict-set! mydict key value))))))

With the (make-vector 8), above, the python dictionary is nearly twice as
fast as the guile hash.

With (make-vector 1024), instead, the python dictionary is 50% faster. 

The python dictionary's internal hash table has a default initial length
of 4.  So, maybe (make-vector 4) would be a bit more fair.

>  - Maciej Stachowiak
> 

	Jay Glascoe
	jglascoe@jay.giss.nasa.gov