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Hashes and arrays can both be implemented as in memory data structures, or on disk data structures. Therefore it is perfectly reasonable to talk about what each looks like in memory and on disk.

In Perl the two options don't even look different for hashes, you just add an appropriate tie. The difference is slightly larger for arrays because you don't want to use the built-in sort on a large array that lives on disk.

As for my duplicates comment, I am not denying that a hash is better than an array whether or not there are duplicates. However the speed of accessing a hash is basically independent of how many duplicates there are in your incoming data structure. (There are subtle variations depending on, for instance, whether you are just before or after a hash split, but let's ignore that.) The speed of doing a merge sort that eliminates duplicates ASAP varies greatly depending on the mix of duplicates in your incoming data structure. Therefore the array solution improves relative to the hash as you increase the number of duplicates. This doesn't make the array solution

In fact in the extreme case where you have a fixed number of distinct lines in your data structure, the array solution improves from O(n log(n)) to O(n). The hash solution does not improve, it is O(n) regardless.


In reply to Re^4: mathematical proof by tilly
in thread mathematical proof by donkeykong

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    [stevieb]: Corion I like the groundbreaking ones (guitar players). I have the ability to pick up on sounds that are groundbreaking or specific to a person, thanks to my years of doing recording/mixing/ sampling (hip-hop mind you, but years of it...
    [stevieb]: ...has honed in my skills of recognizing sound
    [stevieb]: All of the early members are coming out of the woodwork today :) Hey, planetscape
    [Corion]: This cover version had so much promise but the singing is underwhelming :-/
    [stevieb]: erix Thanks! I dislike remakes of songs usually, but my favourite remix of guitar/weeps is Jeff Healey. I'll take a listen to yours
    [planetscape]: hi stevieb!
    [stonecolddevin]: also hi Corion
    [Corion]: stevieb: Yeah, but I don't follow guitar players enough... I never got Prince and I don't think I could recognize his play style. I can recognize Santana and Nile Rodgers, but that's about it, and not really deep knowledge I think ;)
    [stevieb]: Jeff Healey cut of My guitar gently weeps
    [stonecolddevin]: you don't recognize Prince. Prince tells you it's him.

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