Re: [h-e-w] ediff speed, 21.1 vs 20

[Bill Pringlemeir]

 Stephen> I've been usingn Gnu Emacs 21.1 for a few months now, and I
 Stephen> like it.  However, it has one drawback compared to Emacs 20;
 Stephen> ediff has slowed down tremendously, for diff sections that
 Stephen> are multiple lines.

I have experienced the same thing. 

 "GNU Emacs 21.2.1 (i386-msvc-nt4.0.1381) of 2002-03-19 on BILL"

It seems to be related to large difference regions [at least refined
regions].  It also finds ediff-directories finds between files with
different line endings (Unix/DOS), but when ediff runs on the files,
there is no difference.

 Stephen> Does anyone have a clue why it slowed down so much, or how
 Stephen> to speed it back up?

I don't think that this line ending stuff happened before.  A vague
clue?

        Size   Last modified           Name
    ----------------------------------------------

    Session 1:
        46283   Nov 30 2000 14:44:47   e:/emacs-20.7/lisp/ediff-diff.el
        47302   Jul 21 2001 02:28:24   e:/src/emacs-21.2/lisp/ediff-diff.el
    Session 2:
        13584   May  4 1998 19:33:16   e:/emacs-20.7/lisp/ediff-help.el
        13540   Jul 16 2001 04:46:48   e:/src/emacs-21.2/lisp/ediff-help.el
    Session 3:
        13691   May  4 1998 19:33:18   e:/emacs-20.7/lisp/ediff-hook.el
        13828   Jul 16 2001 04:46:48   e:/src/emacs-21.2/lisp/ediff-hook.el
    Session 4:
        68043   Nov 11 1998 20:54:52   e:/emacs-20.7/lisp/ediff-init.el
        69645   Sep  9 2001 19:33:38   e:/src/emacs-21.2/lisp/ediff-init.el
    Session 5:
        11795   May  4 1998 19:33:20   e:/emacs-20.7/lisp/ediff-merg.el
        14487   Jul 16 2001 04:46:48   e:/src/emacs-21.2/lisp/ediff-merg.el
    Session 6:
        79338   May 30 1998 11:32:04   e:/emacs-20.7/lisp/ediff-mult.el
        80375   Sep 28 2001 00:06:09   e:/src/emacs-21.2/lisp/ediff-mult.el
    Session 7:
        26433   Nov 30 2000 16:10:48   e:/emacs-20.7/lisp/ediff-ptch.el
        27375   Jul 21 2001 02:28:24   e:/src/emacs-21.2/lisp/ediff-ptch.el
    Session 8:
       139349   May  2 2000 09:47:00   e:/emacs-20.7/lisp/ediff-util.el
       142708   Jul 21 2001 02:28:24   e:/src/emacs-21.2/lisp/ediff-util.el
    Session 9:
        13492   May  4 1998 19:33:28   e:/emacs-20.7/lisp/ediff-vers.el
        10174   Jul 16 2001 04:46:48   e:/src/emacs-21.2/lisp/ediff-vers.el
    Session 10:
        47005   May  4 1998 19:33:32   e:/emacs-20.7/lisp/ediff-wind.el
        46488   Jul 16 2001 04:46:48   e:/src/emacs-21.2/lisp/ediff-wind.el

After looking at all the differences, the thing that comes to mind is
the overlays.  I think that the display updating has changed
considerably.  Perhaps overlays and font-lock stuff were calculated
before displaying the buffer previously.  When you whip through the
diffs, hitting `n' for next, there are times when it pauses for a long
time.  This was not the previous behviour... and this is the thing I
notice.  For instance, when diffing "ediff-ptch.el", there are 32
diffs.  When highlighting the 13th, 14th regions, I note a long pause
(longer relative to the lavish spriteness Emacs 20.xx afforded me).
This causes the font-lock to change the highlighting.  I think that
this stuff is precomputed as the areas are highlighted prior to this.
However, the area is a single color.  I don't know when the refinement
is done, but when that region is active, there are now multiple
colours.  Note too much help...

fwiw,
Bill Pringlemeir.