Date: Fri, 16 Jul 1999 18:30:45 -0400
From: Igor Schein <igor AT txc DOT com>
To: derrick AT cco DOT caltech DOT edu
Cc: pgcc AT delorie DOT com
Subject: Re: Do underflows cause a slowdown? Can I fix it?
Message-Id: <19990716183045.J24321@deimos.txc.com>
References: <378F9D37 DOT EC6D3B6B AT cco DOT caltech DOT edu>
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In-Reply-To: <378F9D37.EC6D3B6B@cco.caltech.edu>; from Derrick Bass on Fri, Jul 16, 1999 at 01:59:35PM -0700
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On Fri, Jul 16, 1999 at 01:59:35PM -0700, Derrick Bass wrote:
> I am using a Pentium Pro (180 MHz, Redhat 5.2) and some of my FP
> intesive code occassionally slows by a factor of 4-6.  I think I've
> traced this to underflow. . .
> 
> Does handling underflow slow down floating point?  Is there a compiler

It definitely does.

> switch or library call to make the underflows silently get replaced by
> zero?

Look at -mfp-trap-mode flag.

Igor