A simple program to measure list accumulation performance

accum.ss

(import :std/srfi/1
        :std/misc/list
        :gerbil/gambit/os)
(export main)

(def (accum1 lst)
  (let lp ((rest lst) (r []))
    (match rest
      ([e . rest]
       (lp rest (cons e r)))
      (else
       (reverse! r)))))

(def (accum2 lst)
  (let (root [#f])
    (let lp ((rest lst) (tl root))
      (match rest
        ([e . rest]
         (let (tl* [e])
           (set! (cdr tl) tl*)
           (lp rest tl*)))
        (else
         (cdr root))))))

(def (accum3 lst)
  (with-list-builder (push)
    (let lp ((rest lst))
      (match rest
        ([e . rest]
         (push e)
         (lp rest))
        (else (void))))))

(def (main n)
  (let* ((N (string->number n))
         (lst (iota N)))
    (##gc)
    (time (accum1 lst))
    (##gc)
    (time (accum2 lst))
    (##gc)
    (time (accum3 lst))))

It seems we had some very weird cpu caching effects; also gc minor faults!
I think the separate test restores sanity.