On 8/16/11 9:29 PM, bearophile wrote:
Walter Bright:
I think there are search trees like the Red-Black ones that guarantee a O(n ln
n) worst case. I am wrong?
Just feed it more data.
If you feed it more data, even if all items pruce collision because they all
hash to the same bucket, if you use Red-Black trees to handle the items in the
same bucket you keep having a O(n ln n) behaviour, that's usually fast enough.
With Python and the new D AAs you instead get a quadratic one. This quadratic
behaviour gives troubles way before the physical RAM is exhausted.
Bye,
bearophile
Let's please stop this. Many of us, including yourself, noticed the
relatively poor performance of D's previous hashtables compared to other
languages. Switching to singly-list collision handling marked an
improvement. Now a lot of data structure designs have a worst-case that
makes them perform worse than others. If you worry about attacks, please
implement your own hashtable. If we switch back to the old
implementation, you'll complain again about D's hashtables being slower
than Python's, thus closing a years-long cycle.
Thanks,
Andrei
