Walter Prins wrote:
On 19 July 2012 23:20, Steven D'Aprano <st...@pearwood.info> wrote:
Selby Rowley-Cannon wrote:
I am using a hash table in a small randomization program. I know that some
hash functions can be prone to collisions, so I need a way to detect
collisions.
This entire question seems like a remarkable case of premature optimization.
Start with demonstrating that collisions are an actual problem that need
fixing.
Unless you know all the keys in advance and have consructed a proven
perfect hash, potential collisions are something that *any* hash table
implementation fundamentally *has* to deal with, no matter how small
the probability of a collision. (If there's a non-zero probability of
collision you *have* to deal with collisions.)
Absolutely. And did you think that Python, a 20 year old language which uses
dicts (hash tables) as a fundamental data structure for its own internals,
somehow neglected to do so? (A rhetorical question, I know you didn't :)
Naturally dictionaries (hash tables) deal with collisions. They couldn't work
if they didn't.
[...]
But yes, rolling your own is not a good idea given highly optimized
solutions already exist inside the Python language (dict) Except of
course if you're studying hash tables as part of some course...
Ah, of course that would be an excellent reason for writing your own hash
table implementation! I didn't think of that at the time.
--
Steven
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