Is there ever a good reason to use Insertion Sort?

Question

For general-purpose sorting, the answer appears to be no, as quick sort, merge sort and heap sort tend to perform better in the average- and worst-case scenarios. However, i

Answer 1

An important concept in analysis of algorithms is asymptotic analysis. In the case of two algorithms with different asymptotic running times, such as one O(n^2) and one O(nlogn) as is the case with insertion sort and quicksort respectively, it is not definite that one is faster than the other.

The important distinction with this sort of analysis is that for sufficiently large N, one algorithm will be faster than another. When analyzing an algorithm down to a term like O(nlogn), you drop constants. When realistically analyzing the running of an algorithm, those constants will be important only for situations of small n.

So what does this mean? That means for certain small n, some algorithms are faster. This article from EmbeddedGurus.net includes an interesting perspective on choosing different sorting algorithms in the case of a limited space (16k) and limited memory system. Of course, the article references only sorting a list of 20 integers, so larger orders of n is irrelevant. Shorter code and less memory consumption (as well as avoiding recursion) were ultimately more important decisions.

Insertion sort has low overhead, it can be written fairly succinctly, and it has several two key benefits: it is stable, and it has a fairly fast running case when the input is nearly sorted.