(defun gnus-update-read-articles (group unread &optional compute)
  "Update the list of read articles in GROUP."
  (let* ((active (or gnus-newsgroup-active (gnus-active group)))
	 (entry (gnus-gethash group gnus-newsrc-hashtb))
	 (info (nth 2 entry))
	 (prev 1)
	 (unread (sort (copy-sequence unread) '<))
	 read)
    (if (or (not info) (not active))
	;; There is no info on this group if it was, in fact,
	;; killed.  Gnus stores no information on killed groups, so
	;; there's nothing to be done.
	;; One could store the information somewhere temporarily,
	;; perhaps...  Hmmm...
	()
      ;; Remove any negative articles numbers.
      (while (and unread (< (car unread) 0))
	(setq unread (cdr unread)))
      ;; Remove any expired article numbers
      (while (and unread (< (car unread) (car active)))
	(setq unread (cdr unread)))
      ;; Compute the ranges of read articles by looking at the list of
      ;; unread articles.
      (while unread
	(when (/= (car unread) prev)
	  (push (if (= prev (1- (car unread))) prev
		  (cons prev (1- (car unread))))
		read))
	(setq prev (1+ (car unread)))
	(setq unread (cdr unread)))
      (when (<= prev (cdr active))
	(push (cons prev (cdr active)) read))
      (setq read (if (> (length read) 1) (nreverse read) read))
      (if compute
	  read
	(save-excursion
	  (set-buffer gnus-group-buffer)
	  (gnus-undo-register
	    `(progn
	       (gnus-info-set-marks ',info ',(gnus-info-marks info) t)
	       (gnus-info-set-read ',info ',(gnus-info-read info))
	       (gnus-get-unread-articles-in-group ',info (gnus-active ,group))
	       (gnus-group-update-group ,group t))))
       ;; Propagate the read marks to the backend.
       (if (gnus-check-backend-function 'request-set-mark group)
           (let ((del (gnus-remove-from-range (gnus-info-read info) read))
                 (add (gnus-remove-from-range read (gnus-info-read info))))
             (when (or add del)
               (gnus-request-set-mark
                group (delq nil (list (if add (list add 'add '(read)))
                                      (if del (list del 'del '(read)))))))))
	;; Enter this list into the group info.
	(gnus-info-set-read info read)
	;; Set the number of unread articles in gnus-newsrc-hashtb.
	(gnus-get-unread-articles-in-group info (gnus-active group))
	t))))