Author: James Swafford
Date: 09:25:12 01/15/00
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On January 15, 2000 at 11:38:53, Daniel Clausen wrote: >Hi > >On January 15, 2000 at 09:40:51, James Swafford wrote: > >[snip] > >>If you use 20 bits to probe, why not just store the other 44 bits in the >>table as a checksum? You already know the other 20 bits match.... >> >>I use a "minimum size", so my key is guaranteed to be N bits long. >>My tables only use 64-N bits as the checksum. > >This surely will work too. I think most people don't do it because >of one of the following reasons: I know. :-) That's why I do it. > >1. Most peoples hashentry is 128 bit wide. So if they use 64bit for > the complete hashkey, they still have 64 bit left. And for most > people this is more than enough. > >2. If you store only the 64-N bits in your hashentry, the size of > the hashentry changes if you change the hashtable size. Yeah, it can get kind of sticky if you allow the 64-N bits to be dynamic, but I don't. The drawback is that I have to use a minimum hash table size (key), but that's not a problem with modern machines. > >3. If you would keep the hashentry-size constant (eg 128 bit) even > when you change the hashtable-size, you have a non-contant number > of bits you can use for storing additional info. It's not easy > to use this though. > >Hope this made some sense. Of course. :-) > >Kind regards, > -sargon
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