Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!newstop!texsun!convex!eugene!swarren
From: swarren@eugene.uucp (Steve Warren)
Newsgroups: comp.arch
Subject: Re: hardware complex arithmetic support
Message-ID: <1549@convex.UUCP>
Date: 18 Aug 89 21:23:30 GMT
References:  <1672@crdgw1.crd.ge.com> <4781@freja.diku.dk> <1758@crdgw1.crd.ge.com>
Sender: usenet@convex.UUCP
Reply-To: swarren@eugene.UUCP (Steve Warren)
Organization: Convex Computer Corporation, Richardson, Tx.
Lines: 20

In article <1758@crdgw1.crd.ge.com> davidsen@crdos1.UUCP(bill davidsen) writes:
>  Could you 'splain this to me? It sounds as if you are saying that if
>one component is large in magnitude we can afford to have less precision
>on the other. Hope I misunderstand what you're telling me.
>	bill davidsen		(davidsen@crdos1.crd.GE.COM)
>  {uunet | philabs}!crdgw1!crdos1!davidsen
>"Stupidity, like virtue, is its own reward" -me

Think of it as a vector.  Changing the mantissa of the component that is
orders of magnitude smaller is not going to move the vector significantly.

For example, if the magnitude of the smaller (call it V1) of the two
components is less than the least significant bit of the larger component
(call it V2), then the truncation error introduced by V2 is greater than
the error introduced by eliminating V1 entirely.  V1 therefore should be
truncated at the least significant position in V2.

--Steve
-------------------------------------------------------------------------
	  {uunet,sun}!convex!swarren; swarren@convex.COM