Re: Request for motion Fwd: Input from IFIP WG 2.5 to IEEE Interval Standards Working GroupŮ
In reply to Dan Zuras, Arnold Neumaier wrote:
> It is impossible to choose an element from an empty set, ...
I am sure Dan was referring to a *vector* element, i.e. we are dealing
here with vectors of intervals.
The situation is analogous in some ways to a two-operand operation
where one operand is Empty or NaI -- but in that case we have clear
propagation rules. Those rules may however be INAPPROPRIATE for
operations involving possibly large vectors, for a number of reasons.
One of these is that implementations should be allowed to partition
the argument set and parallelise without affecting the final result
(unlike reduction operations, which give some latitude here). Another
reason is to avoid throwing away a large amount of work if one of the
operands has a problem -- and to avoid the need to pre-scan operands.
So I would be careful to describe the 754-2008 rules as "buggy". I
would have to go through the voluminous stds-754 correspondence to
remind myself of what the arguments were for the exceptional rules,
so I won't comment further (other than to agree that I was surprised
too when I came across them).
Michel.
---Sent: 2009-09-11 09:23:40 UTC