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From: jbs@WATSON.IBM.COM
Newsgroups: comp.arch
Subject: IEEE arithmetic (Goldberg paper)
Message-ID: <9106120018.AA18733@ucbvax.Berkeley.EDU>
Date: 12 Jun 91 00:00:27 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 29


         I said:
 >          I don't believe interval arithmetic is used enough to justify
 > any hardware support.
         Dik Winter said:
Well, IBM thought it important enough to provide support in some models (43xx).
Acrith is the keyword.

         Ah Acrith, I will let Kahan comment ("Anomalies in the IBM
Acrith Package" by W. Kahan and E. LeBlanc, Version dated March 13,
1985, p. 9):
         "ACRITH is not at all typical of IBM products but seems instead
first to have escaped prematurely from a research project and then to
have evaded quality controls."
         I said:
 >                                                                      In
 > any case I believe your estimate of 3x slower than straight floating
 > point is unrealistic.
         Dik Winter said
How come unrealistic?  Example, interval add a to b giving c:
        set round to - inf;
        c.low = a.low + b.low;
        set round to + inf;
        c.upp = a.upp + b.upp;
why would this be more than 3x slower than straight floating point?

        Because it's 4 instructions vrs 1.  Also lets see your code
for interval multiplication.
                    James B. Shearer