relative benefit of .reserve and .length

[Jay Norwood via Digitalmars-d-learn]

I timed some code recently and found that .reserve made almost no 
improvement when appending.  It appears that the actual change to 
the length by the append had a very high overhead of something 
over 200 instructions executed, regardless if the .reserve was 
done.  This was a simple append to an integer array.

The only way I found to avoid this was to set the length outside 
the loop and update the array values by index.  That was on the 
order of 10x faster.