Function to print a diamond shape

["Luís]

On Saturday, 22 March 2014 at 14:41:48 UTC, Jay Norwood wrote:
> The computation times of different methods can differ a lot.   
> How do you suggest to measure this effectively without the 
> overhead of the write and writeln output?   Would a count of 
> 100001 and stubs like below be reasonable, or would there be 
> something else that would  prevent the optimizer from getting 
> too aggressive?

I used this to benchmark H. S. Teoh's calendar formatter:

version(benchmark)
{
     int main(string[] args)
     {
         enum MonthsPerRow = 3;
         auto t = benchmark!(function() {
                 foreach(formattedYear; iota(1800, 2000).map!(year 
=> formatYear(year, MonthsPerRow)))
                 {
                     foreach(_; formattedYear){};
                 }
             })(30);
         writeln(t[0].msecs * 0.001);
         return 0;
     }
}

While the optimizer could probably remove all of that, it 
doesn't. I also tested it against other options like walkLength, 
this ended up begin the better choice.

(BTW, using joiner instead of join I was able to more than double 
the performance: 
https://github.com/luismarques/dcal/tree/benchmark . Once the 
pipeline is made lazy end to end that will probably have even 
more impact.)