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X-Authentication-Warning: slinky.cs.nyu.edu: pechtcha owned process doing -bs
Date: Fri, 18 Jun 2004 23:10:45 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: "Douglas A. Vechinski" <douglas DOT vechinski AT dynetics DOT com>
cc: cygwin AT cygwin DOT com
Subject: Re: Poor execution speeds using -mno-cygwin g77 option
In-Reply-To: <40D353CA.7010905@dynetics.com>
Message-ID: <Pine.GSO.4.58.0406182302440.3356@slinky.cs.nyu.edu>
References: <40D34454 DOT 4050103 AT dynetics DOT com> <Pine DOT GSO DOT 4 DOT 58 DOT 0406181544140 DOT 3356 AT slinky DOT cs DOT nyu DOT edu> <40D353CA DOT 7010905 AT dynetics DOT com>
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On Fri, 18 Jun 2004, Douglas A. Vechinski wrote:

> Igor Pechtchanski wrote:
>
> >>Even though Case C, when the -mno-cygwin flag is not used, the
> >>difference is still significant. compared to Case A.
> >
> >That's not surprising.  Cygwin is a POSIX emulation environment *on top*
> >of Windows -- naturally the performance of any Cygwin tool will be slower
> >than that of an equivalent pure Windows tool.  The MinGW case is
> >surprising, but doesn't belong on this list.
>
> I was planning on sending the question to Mingw32.  I never have been
> totally clear on how separate and distinct Cygwin and Mingw32 are.

Cygwin is a POSIX emulation environment.  MinGW32 is a static mapping from
some POSIX calls to the corresponding Win32 API calls.  They are separate
projects.  Think of Cygwin as a runtime module that wraps all POSIX calls,
and of MinGW as a compile-time mapping.  That's why MinGW produces pure
Windows executables.

> >>Is this a Cygwin problem, or g77 problem or something else.  I don't
> >>recall experiencing such differences several years ago when doing the
> >>same thing.
> >
> >Things evolve.  It's possible that some system calls got speeded up on
> >Linux (or, though doubtful, that some system calls got slowed down on
> >Windows).  Are you using the same exact options to compile (keep in mind
> >that the defaults may be different on Linux and Cygwin)?  As a WAG, are
> >you using floating point emulation instead of hardware?
>
> I supply the same compiler flags to both under Linux and Cygwin (-O and
> some -D defines).

Check the default compilation options (*not* the command-line flags).
Since you only use the "-O" flag, check whether the Linux gcc and the
Cygwin one have the same defaults (I believe they are called "specs", "gcc
-dumpspecs"  should show some of them).

> To my knowledge, I'm not using floating point emulation.  But if I was,
> how would I be able to check?

Actually, my WAG may turn out to be right after all.  Check the default
target architecture (processor) for both Linux and Cygwin -- you might
find that the default target for Cygwin is i386, and for Linux it's
something like i686/pentiumpro.

Otherwise, your best bet would probably be profiling.
	Igor
-- 
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     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
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