Different array rotation algorithms benchmark

[Miguel L via Digitalmars-d-learn]

On Thursday, 1 September 2016 at 09:36:16 UTC, Miguel L wrote:
> Hi
>
> I recently needed a very optimized array rotation algorithm, so 
> I did this benchmark, hope you find it interesting. I am a bit 
> surprised by the poor results of std.algorithm.bringToFront:
>
> [...]

Sorry Rotate4 had a bug, there was an extra for that was not 
neccesary, this is the correct implementation:

void Rotate4(T)(T[] input, long n) pure
{
	/* 1,2,3,4,5,6,7,8 - 2 -
	 * 7,2,3,4,5,6,1,8 - a=0 b=8-2=6
	 * 7,8,3,4,5,6,1,2 - a=1 b=7
	 * 7,8,1,4,5,6,3,2 - a=2 b=6
	 * 7,8,1,2,5,6,3,4 - a=3 b=7
	 * 7,8,1,2,3,6,5,4 - a=4 b=6
	 * 7,8,1,2,3,4,5,6 - a=5 b=7
--------------------
        1,2,3,4,5,6,7,8,9 - 3 -
	 * 7,2,3,4,5,6,1,8,9 - a=0 b=9-3=6
	 * 7,8,3,4,5,6,1,2,9 - a=1 b=7
	 * 7,8,9,4,5,6,1,2,3 - a=2 b=8
	 * 7,8,9,1,5,6,4,2,3 - a=3 b=6
	 * 7,8,9,1,2,6,4,5,3 - a=4 b=7
	 * 7,8,9,1,2,3,4,5,6 - a=5 b=8
	 */
	if(n<0)
		n=input.length+n;

	long a=0,b=input.length-n;
	T tmp;

	while(a<input.length-n-1)
	{
		tmp=input[b];
		input[b]=input[a];
		input[a]=tmp;
		++a;
		++b;
		if(b>=input.length)
			{
			b=input.length-n;
			}
	}

}