Performance of ranges verses direct

[Joseph Rushton Wakeling]

On 11/12/13 11:10, John Colvin wrote:
> A lot of the performance loss is down to missed optimisations, in particular
> inlining.

Simple example:

     foreach(i; iota(0, 10)) { ... }

should be as fast as

     foreach(i; 0 .. 10) { ... }

but isn't.  I remember Andrei noting that this ought to be easily fixable [*], 
but I don't know if that actually happened, because I haven't compared the two 
recently.

[* If I recall right, it's achievable by special-casing iota when the increment 
is 1, but don't quote me on that.]

> General advice: use ranges, std.range and std.algorithm wherever possible.
> Profile the resulting code and write out the hotspots in an imperative style to
> see if you can squeeze out some extra speed.

Yes -- use ranges as much as possible because the resulting code will be so much 
easier to read and maintain.  Switching to imperative style is only worth it if 
there's a speed problem (read: "The speed is unsatisfactory for your use case 
and/or inferior to rival programs doing the same thing.").