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From: Mikhail Teterin <mi AT corbulon DOT video-collage DOT com>
Message-Id: <200212211447.gBLElNsH041540@corbulon.video-collage.com>
Subject: Re: poor performance -- is Cygwin to blame?..
In-Reply-To: <1040424904.bd9d0620tprince@myrealbox.com>
To: Timothy C Prince <tprince AT myrealbox DOT com>
Date: Sat, 21 Dec 2002 09:47:23 -0500 (EST)
CC: cygwin AT cygwin DOT com
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X-Scanned-By: MIMEDefang 2.21 (www . roaringpenguin . com / mimedefang)

> In my experience with MPI programs, comparing cygwin and linux,
> message passing takes longer under cygwin, but the time may be made up
> elsewhere, if the compilation is truly similar.
>
> You mention that considerable time is spent in log(), pow(), exp()
> but leave us guessing how you implemented them.

I did not implement them. They are from whatever -lm means on Cygwin. I
use them to compute my own formula repeatedly for hundreds of different
vectors.

> Then you imply that you think cygwin, rather than your math functions,
> is the speed determining factor, without giving us a means to judge.

They are not mine. There must be a misunderstanding...

> The glibc versions of these functions are much faster than the newlib
> versions, particularly if you permit the use of <mathinline.h>.
> Neither approach the potential of pentium4, but the simplest way to
> speed them up on cygwin is to employ something like <mathinline.h>,
> and to provide your own pow() (or to use a compiler and library which
> targets pentium4).

Can this be done with just CFLAGS? I really don't want to pollute my
code with ``#ifdef CYGWIN''... Thank you,

	-mi

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