On 9/19/06, A. M. Archibald <[EMAIL PROTECTED]> wrote:
Looks like mergesort can be modified to sort around the NaNs without too much trouble if there is a good isnan function available: just cause the pointers to skip over them. I see that most of the isnan stuff seems to be in the ufunc source and isn't terribly simple. Could be broken out into a separate include, I suppose.
I still wonder if it is worth the trouble. As to raising an exception, I seem to recall reading somewhere that exception code tends to be expensive, I haven't done any benchmarks myself.
Chuck
On 19/09/06, Charles R Harris <[EMAIL PROTECTED]> wrote:
>
>
>
> For floats we could use something like:
>
> lessthan(a,b) := a < b || (a == nan && b != nan)
>
> Which would put all the nans at one end and might not add too much overhead.
You could put an any(isnan()) out front and run this slower version
only if there are any NaNs (also, you can't use == for NaNs, you have
to use C isNaN). But I'm starting to see the wisdom in simply throwing
an exception, since sorting is not well-defined with NaNs.
Looks like mergesort can be modified to sort around the NaNs without too much trouble if there is a good isnan function available: just cause the pointers to skip over them. I see that most of the isnan stuff seems to be in the ufunc source and isn't terribly simple. Could be broken out into a separate include, I suppose.
I still wonder if it is worth the trouble. As to raising an exception, I seem to recall reading somewhere that exception code tends to be expensive, I haven't done any benchmarks myself.
Chuck
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