Re: Wording of the rationale Per Bothner (08 Nov 2006 02:53 UTC)
Re: Wording of the rationale Per Bothner 08 Nov 2006 02:53 UTC
Jens Axel Søgaard wrote:
> * Four varieties of algorithms were provided (quick, heap,
> insert, merge) even though quick, heap, and insert sorts have
> no significant advantage over merge-sort.
> Second: What does "no significant advantage" mean? I were of the
> impression, that the "hidden constants" of O(n log (n)) of
> vector-quick-sort were smaller than that of vector-merge-sort.
My impression is that is non-trivially faster when you're sorting an
array of integers, with no indirection through a "compare" function.
In practice, one (almost) never sorts an array of integers (one sorts
an array of records/objects - which may have integer fields), and one
usually indirects though a compare function. That changes the "constant
It is illustrative that java.util.Arrays uses a "tuned quicksort" for
sorting arrays of "primitive" (unboxed) numbers, but a "modified
mergesort" to sort Object arrays.
> Also: Is merge-sort the fastest algorithm, if the elements are "almost
From the Java documentation:
This [modified merge-sort] algorithm offers guaranteed n*log(n)
performance, and can approach linear performance on nearly sorted