Simple performance question from a newcomer

[Kapps via Digitalmars-d-learn]

On Monday, 22 February 2016 at 07:10:23 UTC, Kapps wrote:
> If you do want to test the differences between the range 
> approach and the loop approach, something like:
> auto sumtest4(Range)(Range range) @safe pure {
> 	return range.reduce!((a, b) => a + b);
> }
> is a more fair comparison. I get results within 15% of sumtest2 
> with this using dmd. I think with ldc this would be identical, 
> but the version in homebrew is too old to compile this.

Using LDC with the mir version of ndslice so it compiles, and the 
following code:
sw.reset();
sw.start();
foreach (unused; 0..times) {
	for (int i=0; i<N; ++i) {
		res4[i] = sumtest4(f[i]);
	}
}
t3 = sw.peek().msecs;

and

auto sumtest4(Range)(Range range) {
	return range.reduce!((a, b) => a + b);
}

I get:
145 ms
19 ms
19 ms
19 ms

So, with LDC, there is no performance hit doing this. The only 
performance hit is when .sum uses a different algorithm for a 
more accurate result. Also, the LDC version appears to be roughly 
5x faster than the DMD version.