(defun key-quiz--shuffle-list (list)
  "Shuffles LIST randomly, modying it in-place."
  (dolist (i (reverse (number-sequence 1 (1- (length list)))))
    (let ((j (random (1+ i)))
	  (tmp (elt list i)))
      (setf (elt list i) (elt list j))
      (setf (elt list j) tmp)))
  list)

(defun key-quiz--shuffle-list-nreverse (list)
  "Shuffles LIST randomly, modying it in-place."
  (dolist (i (nreverse (number-sequence 1 (1- (length list)))))
    (let ((j (random (1+ i)))
	  (tmp (elt list i)))
      (setf (elt list i) (elt list j))
      (setf (elt list j) tmp)))
  list)

(defun elfeed--shuffle (seq)
  "Destructively shuffle SEQ."
  (let ((n (length seq)))
    (prog1 seq                  ; don't use dotimes result (bug#16206)
      (dotimes (i n)
        (cl-rotatef (elt seq i) (elt seq (+ i (random (- n i)))))))))

(defun faster-seq-sort-by (function pred sequence)
  "Sort SEQUENCE using PRED as a comparison function.
Elements of SEQUENCE are transformed by FUNCTION before being
sorted.  FUNCTION must be a function of one argument."
  ;; This version is modified to avoid calling "random" twice every time the predicate is called.
  (seq-map 'cdr
           (sort (seq-map (lambda (x) (cons (funcall function x) x)) sequence)
                 (lambda (a b)
                   (funcall pred (car a) (car b))))))

(defun seq-sort-by--shuffle (seq)
  (seq-sort-by (lambda (_) (random)) #'<= seq))

(defun faster-seq-sort-by--shuffle (seq)
  (faster-seq-sort-by (lambda (_) (random)) #'<= seq))

(dolist (sorter '(key-quiz--shuffle-list
                  key-quiz--shuffle-list-nreverse
                  elfeed--shuffle
                  seq-sort-by--shuffle
                  faster-seq-sort-by--shuffle
                  ))
  (dolist (list-type '(list vector))
    (let ((big-list (seq-into (seq-take obarray 5000) list-type))
          (reps 100)
          ;;(gc-cons-threshold  (* 128 1024 1024))
          )
      (message "*** %s - %s:" list-type sorter)
      (garbage-collect)
      (benchmark reps `(funcall ',sorter big-list))
      )))