Re: Fastest Way to Append Multiple Elements to an Array

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/19/14 5:28 PM, Anonymous wrote:

What a big surprise. If you make an array of struct, each item of your
array has the length of the struct. structs a values.
If you want to append a struct to an array just append a pointer to
the struct:

----------
struct arg{uint a,r,g,h;};

arg * [] argh;
arg [] argv;

foreach(immutable i; 0..1000)
  argh ~= new arg;
----------

so in argh, each item is a size_t pointer. damn.
In argv, the delta between each item is
(a.sizeof+r.sizeof+g.sizeof+h.sizeof)
In argh, the delta between each item is (arg *).sizeof

argv needs to be a contiguous thing so it's slower to append because
it's not just storing a reference but the whole thing. There is
consequently more realloc().
argh is faster because it stores the addresses of the items.

argv appends maybe 33 bytes, 33 bytes and so on.
argh always appens 4 4 4... (32 bits OS) or 8 8 8...(64 bits OS). It's
faster , always aligned...page-aware.that's all.

Oh Oh oh.

I'm not sure what you are saying here, sorry.

-Steve