Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!uw-june!rik
From: rik@june.cs.washington.edu (Rik Littlefield)
Newsgroups: comp.arch
Subject: Re: 80-bit notes
Message-ID: <7806@june.cs.washington.edu>
Date: 6 Apr 89 18:48:04 GMT
References: <2583@tank.uchicago.edu> <7829@pyr.gatech.EDU> <97749@sun.Eng.Sun.COM>
Organization: U of Washington, Computer Science, Seattle
Lines: 27

In article <97749@sun.Eng.Sun.COM>, khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering) writes:

<  Tom Lahey's fortran for the pc did this [kept 80-bit vars on the 80x87
<  stack during loop execution]. Example:
<  
<  	sum = 0
<  	do i = 1, n
<  	   sum = x(i)*y(i)
<  	end do
<  
<  produces the same answer when sum is dp or sp (x,y, sp..chosen to make
<  this interesting).
<  ........
<  Tom's compiler worked it well enough that some customer's complained.
<  So there is a compiler option that forces gratuitous stores to memory
<  to force the conversion to 32-bits.
<  
<  Of course, this caused the results to be less accurate _AND_ slower.
<  there is no accounting for taste.
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^              

Perhaps these customers wanted to compare their results against other
compilers/machines.  Maybe I'm just pessimistic, but when a new compiler
produces answers that are much different from what I'm used to, "increased
accuracy" is just about the *last* possibility that comes to mind.

--Rik