From:	Russell Wallace <manorsof AT iol DOT ie>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Performance of -lemu
Date:	Fri, 19 Jun 1998 21:46:27 +0100
Organization:	Ireland On-Line
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Message-ID:	<358ACE23.384B@iol.ie>
Reply-To:	manorsof AT iol DOT ie
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To:	djgpp AT delorie DOT com
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I'm working on a program which will make extensive use of floating
point.  I'd like to link with -lemu so it'll work as-is on 386 and 486SX
machines.

However, when I checked the performance of generated code on a simple
benchmark program (multiplying two 100 by 100 matrices, double
precision), I get the following figures on a Pentium-133:

-O3		21 megaflops
-O3 -lemu	13 megaflops

My understanding had been that -lemu should make no difference at all if
the program does in fact end up running on a machine with FP hardware. 
Can anyone explain the reason for this discrepancy, and whether there's
anything that can be done about it?  (Short of forgetting about working
as-is and requiring users of 386s to run one of the .exe emulators,
which is what I'm planning to do as things currently stand.)

-- 
"To summarize the summary of the summary: people are a problem."
Russell Wallace
manorsof AT iol DOT ie

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