why does array appending add a page size instead of doubling ?

[monarch_dodra]

On Sunday, 3 February 2013 at 10:32:10 UTC, timotheecour wrote:
>
>> One more: Did you try using std.container.Array?
>>
>> Even if appender is more optimized than naked array appending, 
>> it still has to work with the underlying system. 
>> std.container.Array should be able to do just as well as 
>> vector, or better (D move semnantics).
>
> it's a bit better (see below for timings), with T=22.628 sec 
> total vs 14s for C++'s std::vector.
>
> Note, I'm not sure how to get address of 1st element in an 
> std.container.Array (is it even possible??? seems like an 
> overreaching limitation for the sake of safety in a system 
> language) so I don't know how to tell the reallocations. But I 
> guess the scheme is clear (reserve(1+3/2*capacity)). In any 
> case, there's still a noticable gap with C++. Also, I'm curious 
> whether you have a reference explaining why 3/2 works better 
> than 2x (as in std::vector) in resizing?

Yeah: std.container.Array does not allow references to its 
internals. D's design is more of a safety first, compared to 
C++'s performance first.