Re: Branch & bound for not everywhere defiend constraints
On 2009-09-02 11:26:21 +0200, Arnold Neumaier wrote:
> Vincent Lefevre schrieb:
> >One could also have a flag attached to the returned interval.
> >Alternatively, one could have a function telling whether X' is
> >included in the domain of f.
>
> The latter can in general be found out only by evaluating;
> so this would double the work whenever one needs both the
> evaluation and the domain check.
I would have said the opposite, i.e. that the latter doesn't need
evaluation in general. For instance, if the domain is R, then the
result is always TRUE. For the division, the result is TRUE iff
the second argument doesn't contain 0.
> Producing NaI in such a situation also wastes information available,
> since one can no longer check for the first two cases
> in the above piece of code.
>
> If flags are to be avoided, flag-raising operations should return
> two results: the range enclosure and a byte encoding all relevant flags.
This is what I've said: a flag *attached to the returned interval*.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)