Re: emacs takes exhorbitantly long to read long, one-line files.

[Randy Yates <yates@digitalsignallabs.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Karl Fogel <kfogel@red-bean.com>
>> Date: Mon, 20 May 2013 09:32:23 -0500
>> Cc: Dmitry Antipov <dmantipov@yandex.ru>
>> 
>> Dmitry Antipov <dmantipov@yandex.ru> writes:
>> >> I already had that in my init.el. I've also tried creating an empty
>> >> file and setting it to fundamental-mode. In both these cases the
>> >> behavior is the same.
>> >
>> >Hm...is it the same with emacs -Q?
>> >
>> >> I did notice that emacs is faster - but still unusably slow - when
>> >> toggle-truncate-lines is true.
>> >
>> >Try (setq-default cache-long-line-scans t) too.
>> 
>> That should help a lot.
>
> But it won't succeed to make Emacs usable with such files.  E.g., try
> this:
>
>   M->
>   C-p
>
> and count the seconds it takes to perform the second command.
>
> What Emacs does behind the scenes is go to the beginning of the
> previous _physical_ line (which is quite fast in this case), and the
> go all the way down the humongously long line, one character at a
> time, until it finds the place to put the cursor.  Unless we make
> radical changes in this algorithm, how can anyone expect reasonable
> performance from this?

I've noticed that xemacs does not have this problem. Would it be
fruitful to look at xemacs' display algorithm?
-- 
Randy Yates
Digital Signal Labs
http://www.digitalsignallabs.com