Template performance

[Stanislav Blinov]

23.11.2010 2:23, bearophile wrote:
> Time ago I have found a little C++ program that computes the number of solutions to the N Queens problem at compile-time using just templates. I have translated it into CTFE code and I have shown in this newsgroup that if your purpose is to compute a result at compile-time, then D CTFE allows you to write much simpler (and faster) code compared to the C++ template mataprogramming.
>
> This time I have translated that C++ code to D code that uses just templates. This is not idiomatic D code, because for this purpose CTFE is better, but templates are used in D too, so it may be a performance benchmark for templates in general.
>
> I am not very good with C++ templates yet, so if you spot an error in my D translation please tell me that I will redo the timings.
>
> Compilation time: G++ 0.96 seconds, dmd 12.4 seconds.
>
> With N=7 G++ uses about 34 MB RAM, DMD about 130+ MB RAM.
>
> I have used MinGW 4.5.1 and DMD 2.050.
>

It'd be good if you also posted the machine specs. I ran the benchmark on
Intel i5 750 with 8Gb RAM under Windows7 Pro x64.

I don't have G++ right now, but I tried cl from Visual Studio 2008 and 
dmc 8.42n instead

Here are the timings (compiler-version-seconds):

dmd 2.050            2.97958
cl  15.00.30729.01   3.65038
dmc 8.42n            11.6375

So at least on this system dmd doesn't look that bad at all.