Re: Would seq-range and seq-mapcat be useful?

[Nicolas Richard]

Le 30/01/2015 17:04, Oleh Krehel a écrit :
> Mine's faster:

I think it will depend on the number of keys.

(defmacro util-timeit (&rest expr)
  `(progn
     (garbage-collect) ;; avoid gc later. maybe.
     (let ((t-beg (float-time))
           (res (dotimes (i 500) ;; I reduced this a bit because I have a slow 
system.
                  ,@expr))
           (t-end (float-time)))
       (/
        (- t-end t-beg)
        500))))

(progn ;; use M-x compile-defun to eval this part
  (defun yf/seq-group-by (fn lst)
    (let ((hash (make-hash-table :test 'equal)))
      (dolist (elm lst)
        (push elm (gethash (funcall fn elm) hash)))
      hash))
  (defun seq-group-by (fn lst)
    (nreverse
     (cl-reduce
      (lambda (acc it)
        (let* ((key (funcall fn it))
               (cell (assoc key acc)))
          (if cell
              (setcdr cell (push it (cdr cell)))
            (push (list key it) acc))
          acc))
      lst
      :initial-value nil))))

(defun make-random-list (n)
  (let ((tmp))
    (dotimes (_ n)
      (push (cons (random 150) t) tmp)) ;; I guess only the keys matter
    tmp))

(let ((tmp (make-random-list 10)))
  (list
   (util-timeit (yf/seq-group-by #'car tmp))
   (util-timeit (seq-group-by #'car tmp))))
(3.778600692749023e-05 3.6581039428710935e-05)


(let ((tmp (make-random-list 100)))
  (list
   (util-timeit (yf/seq-group-by #'car tmp))
   (util-timeit (seq-group-by #'car tmp))))
(0.0002734408378601074 0.0005863599777221679)


(let ((tmp (make-random-list 1000)))
  (list
   (util-timeit (yf/seq-group-by #'car tmp))
   (util-timeit (seq-group-by #'car tmp))))
(0.00434891939163208 0.010494112968444824)

I wasn't really trying to compete though, just giving another point of
view.

-- 
Nico.