On 9/19/06, A. M. Archibald <[EMAIL PROTECTED]> wrote:
Thinking a bit, keeping the values in place isn't easy. Mergesort isn't fixable because values can be moved in front of the nan before it is ever looked at. Nor can it be easily set up to leave all the nans at one end because both a < nan and nan < a return false. Quicksort might be doable with some checks. I mean, what if the selected pivot is a nan? The median of three version used also needs thinking about. Hmm. But I think it is the insertion sort that is messing up the order in mergesort as now nothing will move past the nan even if it has to. That could be fixed, but the nan's would still move around.
I think the best thing to do is punt unless the hardware can be set to do something.
Chuck
On 19/09/06, Charles R Harris <[EMAIL PROTECTED]> wrote:
> If this sort of thing can cause unexpected errors I wonder if it would be
> worth it to have a global debugging flag that essentially causes isnan to
> be called before any function applications.
That sounds very like the IEEE floating-point flags, which would be
extremely useful to have, and which are being wored on, IIRC.
Thinking a bit, keeping the values in place isn't easy. Mergesort isn't fixable because values can be moved in front of the nan before it is ever looked at. Nor can it be easily set up to leave all the nans at one end because both a < nan and nan < a return false. Quicksort might be doable with some checks. I mean, what if the selected pivot is a nan? The median of three version used also needs thinking about. Hmm. But I think it is the insertion sort that is messing up the order in mergesort as now nothing will move past the nan even if it has to. That could be fixed, but the nan's would still move around.
I think the best thing to do is punt unless the hardware can be set to do something.
Chuck
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