Re: Re: zend_fast_hash

At 10:37 AM 5/21/2003 -0400, Sterling Hughes wrote:

On Wed, 2003-05-21 at 11:49, Zeev Suraski wrote: Can you explain how it is simpler? :) Writing a lightweight hash has been on our mind for quite some time, but the reason it never happened is that it appears that most of the places that use hashes actually do take advantage of the non-bare-bones features. The biggest difference I can spot is that there's no linked list that links all of the elements. But if we end up adding apply, and clean (which are actually used a lot outside the scope of symbol tables), and soon enough we'd also need merge, copy and unnamed elements - I'm not sure it's worth the trouble of having two Except for unnamed elements, those are all trivial to implement with the code I've attached. In fact, apply, copy and clean are in there, merge could be done when I figure out the semantics. :) Unnamed elements are impossible, but they should be. If you need unnamed elements, either the code is taking advantage of a feature that shouldn't be there, or one should just use the old hashtable implementation, which will still be available. I dare say that in most cases, using unnamed elements is not necessary.

Let's keep it as simple as possible because if we start adding features it will be zend_hash.*. Only places which need a simple hash should use it and places which need something more powerful should continue to use zend_hash.*

The major API hurdle here is reliance on insertion order, which is used once or twice in the code (not that often, afaik), but I believe that can be changed, and made to work with the new API. I believe I can change over all the symbol tables (EG(function_table), etc.) to use my new hash implementation, and it will be signifigantly faster. I'm holding off on that for now, cause I don't want to muddy the commit/patch.

I don't think EG(function_table) can use it because I think it uses a reverse_apply().

This hashtable implementation requires signifigantly less memory, and has a lower overhead then the standard HashTable. Considering how often hash functions are used in Zend, I think it going to be a big win.

Yep, it has been on my mind for a while but we need to make sure we do it right. Andi