From maintainers-request at octave dot org Mon Sep 26 21:50:43 2005
Subject: Re: speed of octave interpreter
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Paul Kienzle <pkienzle at users dot sourceforge dot net>
Cc: octave maintainers mailing list <maintainers at octave dot org>
Date: Mon, 26 Sep 2005 22:50:36 -0400

On 26-Sep-2005, Paul Kienzle wrote:

| I would be interested to know if the performance on mingw is as
| bad as on cygwin.  Things like make are slow on cygwin compared
| to the same machine on linux, and I think that it is because of
| the file subsystem.

Part of it may be the filesystem.  I think the other thing is the cost
of fork.  From a quick look at the sources, it seems that GNU Make on
Windows uses CreateProcess instead of fork/exec.  I don't see any
special code for Cygwin, so I assume it just does the Unixy thing and
calls fork followed by exec.  On Cygwin, I think this copies the
entire parent process even when the next action is exec (making the
copy unnecessary)..

| Regardless, that doesn't explain the enormous time differences
| observed with ignore_function_timestamp.

I think that was a bug.  I don't see such a dramatic difference with
the current sources (either 2.9.x or the current 2.1.x).  But I also
don't see anything in the diffs between the current 2.1.x sources and
2.1.71 that would account for the difference, so I'm trying to verify
that the bug really is fixed.  I do see the problem in the copy of
2.1.69 that is distributed with Debian testing.

When I run

  strace -o foo.out octave
  ...
  octave> nim_minimax (15)

with 2.1.69, I see an insanely large number of calls to "access" that
should not be happening.

jwe