Hash??? Not quite clear on what this is...

[Markd at Aus.Sun.COM]

johncore at compnect.UUCP (John Core ) writes:

>In article <1990Nov22.235522.26487 at ux1.cso.uiuc.edu>, gordon at osiris.cso.uiuc.edu (John Gordon) writes:
>> avery at netcom.UUCP (Avery Colter) writes:
>> 
>> >I'm seeing all this talk of "Hash Functions".

>...
>College programming courses seem to never deal with the REAL (ie buisness)
>...

>Actually you have to know a lot, like the key's max length
>and how many total records will be in your data base, since you have
>to give the hash function a range to deal with. Example:
>...
>50% of new entries were going into collision.  Took 2 days to rebuild
>the index. 

If you use simplistic static hashing in REAL buisness (sic) you deserve
the heat.  In real life, you need to know neither "the key's max
length", nor "how many total records will be in your data base". 

Dbm in the former, and Dynamic Hashing (and it's numerous variants such
as Probing) in the latter, demonstrate workable techniques that obviate
the need for such prescience.  Both of which have only marginal
relevance to C. 


>--just another old fart telling a war story... 

Quite.


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Mark Delany          markd at Aus.Sun.COM     ...!sun!sunaus!markd
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