Re[6]: Aggregate

[Jeni Tennison <mail@xxxxxxxxxxxxxxxx>]

Mike wrote:
> Yes, Saxon would stop after it found the first one, which on average
> would halve the execution time. But it would still be O(n-squared).

OK. I think my problem lies in the fact that I have never understood
what 0(n-squared) and so on actually means. Presumably this is
something that is taught in beginners' computer-science classes, but
never having attended one I'm still in the dark. My questions are:

1. how can you assess an algorithm to determine its 0(n*)-ness?
2. what implications does that have for methods to use in XSLT/XPath?

> Generally, I would assume that XPath expressions aren't optimised
> unless you have evidence to the contrary. It's earlier days for
> optimizers yet.

Mike, is it possible for you to sketch out the optimisations in Saxon
- for example it's really helpful to know that I should use .. rather
than parent::foo for reasons other than brevity (I tend towards the
latter because it makes explicit where each step is going).

Thanks,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/



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