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bug#15295: python mode slow to unusable
From: |
Stefan Monnier |
Subject: |
bug#15295: python mode slow to unusable |
Date: |
Sun, 27 Oct 2013 00:23:51 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3.50 (gnu/linux) |
Could you take a look at this, as well?
Stefan
>>>>> "Michael" == Michael Heerdegen <michael_heerdegen@web.de> writes:
> Alex V. Koval <alex@ua2web.com> writes:
>> For me this is happen as well. Emacs, starting from version 24.3 became
>> so slow in Python mode that I had to tell all developers at our company
>> to use version 24.2 until I sorted this out.
>>
>> Sit today and started trying various emacs versions, and calling
>> different functions. The suggested test case from original author above,
>> runs with this benchmark:
>>
>> (7.3956507 53 1.8788885930000063)
> I profiled a bit, and, at least in this example, these two functions
> seem to be extremely inefficient in combination:
> (defun python-nav-beginning-of-statement ()
> "Move to start of current statement."
> (interactive "^")
> (while (and (or (back-to-indentation) t)
> (not (bobp))
> (when (or
> (save-excursion
> (forward-line -1)
> (python-info-line-ends-backslash-p))
> (python-syntax-context 'string)
> (python-syntax-context 'paren))
> (forward-line -1))))
> (point-marker))
> (defun python-info-line-ends-backslash-p (&optional line-number)
> "Return non-nil if current line ends with backslash.
> With optional argument LINE-NUMBER, check that line instead."
> (save-excursion
> (save-restriction
> (widen)
> (when line-number
> (python-util-goto-line line-number))
> (while (and (not (eobp))
> (goto-char (line-end-position))
> (python-syntax-context 'paren)
> (not (equal (char-before (point)) ?\\)))
> (forward-line 1))
> (when (equal (char-before) ?\\)
> (point-marker)))))
> They consume most of the time used. While the first function goes
> backward, the second goes forward to the end in every loop cycle. This
> makes the thing O(n^2), with n being the number of lines of the
> expression.
> I don't know Python, so I can't make any suggestions. Who can? At
> least, changing the order of `or' expressions in
> `python-nav-beginning-of-statement' seems to help in the example case:
> (defun python-nav-beginning-of-statement ()
> "Move to start of current statement."
> (interactive "^")
> (while (and (or (back-to-indentation) t)
> (not (bobp))
> (when (or
> (python-syntax-context 'string)
> (python-syntax-context 'paren)
> (save-excursion
> (forward-line -1)
> (python-info-line-ends-backslash-p)))
> (forward-line -1))))
> (point-marker))
> It's also not efficient how often `syntax-ppss' is called all the time.
> Regards,
> Michael.