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bug#50877: 28.0.50; Gnus: nnimap backend is extremely slow to initialise
From: |
Eric Abrahamsen |
Subject: |
bug#50877: 28.0.50; Gnus: nnimap backend is extremely slow to initialise new groups |
Date: |
Tue, 28 Sep 2021 21:25:37 -0700 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Morgan Willcock <mwillcock@precedence.co.uk> writes:
> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>
>> You could try reverting 20f7fa691b7c2859b96550d9ccb326bf394e160d and see
>> if that fixes it. That change went in in April, though, so unless you
>> haven't updated for a while (or you've been seeing this problem for a
>> long time) it might not be likely.
>
> Reverting that commit fixes it for me.
I'm cc'ing Lars and Stefan Kangas, who are the most "involved" here. The
benchmarks are gruesome:
(defun old-gnus-set-difference (list1 list2)
"Return a list of elements of LIST1 that do not appear in LIST2."
(let ((hash2 (make-hash-table :test 'eq))
(result nil))
(dolist (elt list2) (puthash elt t hash2))
(dolist (elt list1)
(unless (gethash elt hash2)
(setq result (cons elt result))))
(nreverse result)))
(let* ((common1 (number-sequence 0 200))
(common2 (number-sequence 501 700))
(l1 (append common1
(number-sequence 200 500 2)
common2))
(l2 (append common1
(number-sequence 201 500 2)
common2))
(results (list
(benchmark-run 1000 (old-gnus-set-difference l1 l2))
(benchmark-run 1000 (seq-difference l1 l2 #'eq)))))
results)->
((1.842791826 7 1.4057783080000021)
(14.284496493999999 4 0.7823414249999985))
This is a particularly bad example -- when there was no common2
`seq-difference' performed better, but I think it still around 6 seconds
to the old function's 2.
Probably still worth a dedicated function for Gnus? (Or a rewrite of
`seq-difference'...)
Eric