Re: I vote NO on Motion P1788/M0024.02:RoundedOperations
On 2011-05-17 14:09:00 +0100, John Pryce wrote:
> So, where and how would the requirement expressed by Ulrich's words,
> or Michel's words, fit into the P1788 document? It's not about
> interval operations as such, but about how to implement them. I can
> see it going into any of
>
> - A "desirable things" section, either in the introductory material
> or in an annex.
Perhaps, but this is something that you cannot change. P1788 is based
on an arithmetic, that can be (or not) a IEEE754 FP arithmetic, and that
a P1788 implementer will not reimplement. From a P1788 implementer's
point of view, what if the requirement expressed by Ulrich's words is
not available?
1. Leave the platform and do not implement an interval arithmetic on it?
2. Implement an interval arithmetic, even though it isn't very efficient?
I think that the P1788 standard shouldn't force the implementer to
choose (1) and shouldn't even recommend it.
> - Level 3, which is about the internal structure of intervals, and how interval operations are implemented in terms of FP operations on their internal fields. Here the standard might include implementations of the interval operations at a pseudo-code level in terms of Ulrich's operations, e.g. Matlab-style
> function z = plus(x,y) %overloads +
> z.inf = x.inf +< y.inf
> z.sup = x.sup +> y.sup;
> end
> That requires a keen volunteer! We can only say these operations SHOULD be implemented by a system, whether hardware or a hardware-software mix -- SHALL is not our business, as Dan & Vincent say.
If +< and +> are not available, there are other ways to implement
the interval function. The absence of these primitives shouldn't
prevent a P1788 implementation from existing.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)