Re: min / max and empty intervals
On Jun 7 2011, Dan Zuras Intervals wrote:
I'd consider this an ill-formed constant, returning canonically
Empty_ill. Whereas if any of the arguments x_i is Empty (with decoration
emp or ill), the returned value is Empty, with the worst decoration of
all the empty arguments. This is consistent and allows for
straightforward debugging.
Oh, I think that's a bit draconian, don't you?
That's what provable RAS is all about! No pain, no gain :-(
Actually, John touched on the reasonable application for
NaNs in a matrix. That of as yet unknown data.
Those aren't NaNs, as specified in IEEE 754 - those are missing values,
as used in statistical software since the 1960s. They have different
semantics, though USUALLY max(<missing>,<value>) should be <missing>;
the only case when it should be <value> is when the max is a reduction
and not a normal operation.
So, I don't know if this applies to the interval world.
In an interactive application, are you interested in
providing assured partial results or waiting until the
input is completed even if its not all needed?
Either - but you don't do that by abusing NaNs or empty intervals.
You do that by coding it properly in terms of operations and reductions,
where the latter allow for the possibility of taking a snapshot. That
is essentially what sequential sampling is in statistics.
Regards,
Nick Maclaren.