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From: jbs@WATSON.IBM.COM
Newsgroups: comp.arch
Subject: Re: Implementing Interval Arithmetic with IEEE rounding modes
Message-ID: <9106190449.AA02871@ucbvax.Berkeley.EDU>
Date: 19 Jun 91 04:28:08 GMT
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         Robert Herdon asked:
While I've seen lots of verbage on the pros and cons of interval
operations, I've seen NO discussion of its impact on algorithms.
The question is then, how does one allow for changes of algorithm
flow because of interval arithmetic?  I.e., any time a decision
is made based on the value of an interval, one sees a dichotomy
of possible flow paths.

         If you are using interval arithmetic to figure error bounds for
a non-interval arithmetic calculation then it is necessary to carry along
the non-interval arithmetic values at each stage as well to get the con-
trol flow correct.  Using the usual interval representation this will in-
crease the cost considerably.  Of course you could represent intervals
as (value, maximum possible absolute error).
                       James B. Shearer