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On Thu, December 15, 2005 17:54, Haufler, Wayne A wrote:
> One of the developers here has the impression /opinion that Perl Hashes
> are slow. That was because of the poor performance of the GUI menu of a
> particular Perl tool, but I believe the poor performance is due to other
> factors. May be able to prove that later.
>
I could not possibly comment on that as I know nothing about your GUI
and/or the way it implements hashes.
> I have browsed through my extensive collection of O'Reilly Perl books,
> and websites, but can't seem to find anything to support my contention
> that hashes are very efficient, almost as much as arrays, and shouldn't
> be avoided.
If you have a set of values, the performance you get by inserting,
deleting, and looking them up is different between an array and hash. I
think I remember that arrays do an O(n) for lookup and deletion, whereas
hashes are better ( O(1) ) for these types of ops. So, if the intensive
part of your algorithm is in the process of looking up values, hashes
should be better than arrays. I do not claim huge experience of large data
sets, as what I currently work with involves some clever pattern matching
on sliced data. But that's what I remember when I used PERL on large data
sets three years ago.
>
> Am I right? Can anyone point me to supporting material?
An article of the PJ with title 'Building a Better Hash with tie' by Dan
Schmidt mentions briefly the issues. Your issue might not be about picking
up random values efficiently, but it does contain a brief discussion on
the pros and cons of arrays and hashes which I liked. Besides, you could
easily prove the point by trying both data structures in your code and
time them. Unless the internals have changed since the article was written
have a look
http://www.dfan.org/real/tpj_hash.html
Only IMHO and sorry in advance if I misundertood something.
--
--
George B. Magklaras
Senior Computer Systems Engineer/UNIX Systems Administrator
The Biotechnology Centre of Oslo,
University of Oslo
URL: http://www.biotek.uio.no
EMBnet Norway: http://www.biotek.uio.no/EMBNET/