In a recent discussion on StackOverflow about performance of arrays vs. lists and for vs. foreach, Jon Skeet created a little microbenchmarking framework and posted his detailed findings on his blog.
First, my local results of the benchmark. I compiled them as Release under VS 2008 SP1. Running without debugging on a Q6600@2.40GHz, .NET 3.5 SP1. They pretty exactly match Jon’s numbers so I won’t duplicate them here, but you can find them in the page’s source.
============ Doubles ============
============ double[] ============
For 1,00
ForHoistLength 1,00
ForEach 1,00
IEnumerableForEach 8,28
Enumerable.Sum 8,27
============ List
For 2,00
ForHoistLength 1,43
ForEach 6,02
IEnumerableForEach 14,03
Enumerable.Sum 14,04
============ Ints ============
============ int[] ============
For 1,00
ForHoistLength 2,06
ForEach 1,38
IEnumerableForEach 15,46
Enumerable.Sum 16,06
============ List
For 2,84
ForHoistLength 3,53
ForEach 4,86
IEnumerableForEach 26,33
Enumerable.Sum 26,33
Out of interest how the differences are when there is more to do in the loop’s body, I added a test suite that formatted the sum as string and appended it to a StringBuilder: