Re: Motion P1788/M007.01_NaI: Discussion period begins
On 2009-08-07 09:32:23 +0200, Arnold Neumaier wrote:
> Michel Hack schrieb:
> >The "illegal construction" NaI is indeed the most important and general
> >one. I believe however that there should also be one for "domain error".
> >That is because in *some* uses of Interval Arithmetic, handling points
> >outside a function's domain as if they did not exist is not desirable,
> >whereas in other uses it is precisely the right thing to do. The Vienna
> >proposal tries to deal with this by recording domain errors in a sticky
> >flag and producing results according to the rule that points outside a
> >function's domain don't contribute to the result set -- but that may lead
> >to a lot of unnecessary calculations when NaI propagation would suffice.
>
> Unfortunately, domain mismatches cannot be accounted for by NaI, since
> the flag should also be raised when evaluating sqrt([-1,1]) = [0,1].
FYI, at the end of June / early July, Dan Zuras and I discussed
privately on a proposal about sticky tags and what could be
considered as different meanings for NaI. I disagreed with Dan's
first proposal (which I found it too complex) but we eventually
converged.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)