Re: Another proposal for a "split" function to complement "mid"
Arnold, P1788
On 20 Mar 2012, at 08:37, Arnold Neumaier wrote:
> On 03/20/2012 07:31 AM, John Pryce wrote:
>>
>> Reminder: Quite a few people have argued in favour of a pragmatic "split" function that always does SOMETHING at Level 2, leaving "midpoint" free to be more mathematical and return NaN for intervals such as [0,inf] that have no midpoint at Level 1. IMHO this is a good idea.
>>
>> What does the group think?
>> - For "split", if we decide to have it, what wins? Reproducibility or freedom?
>> - Is this issue to be decided case by case, or should we have a general policy about it?
>
> In this case, reproducibility is extremely important, as different branching behavior may mak a lot of difference to the performance, may even decide between success and failure.
...
>
> However, there is a _need_ to have a flMedian function (slitting at the median rounded to even of the set of floats in the interval) in the standard, as
> -- its efficient implementation is not straightforward,
> -- it is 100% reproducible, and
> -- it may be profitably used in a B&B scheme,
> -- it will be best at least in certain cases.
I was using "split" loosely to include a function that returns a point to split at. Yes, I agree pretty much with these points, and would vote for a flMedian function that avoids the bunching at zero problem: Michel?
John