"The total size of a static array cannot exceed 16Mb."

[Vladimir Panteleev]

On Tue, 02 Oct 2007 16:18:26 +0300, Christopher Wright <dhasenan at gmail.com> wrote:

> T[][] SquareArray (T) (int x, int y) {
>     T[] block = new T[x * y];
>     T[][] ret = [];
>     ret.length = x;
>     for (int i = 0; i < x; i++) {
>        ret[i] = block[i * y .. (i + 1) * y];
>     }
>
>     return ret;
> }
>
> void main () {
>     int[][] array = SquareArray!(int)(9000, 9000);
> }
>
> Slightly tedious, and it gives you reference semantics and places the
> array on the heap (but do you really *want* 16MB stack frames? I imagine
> the OS might have something to say about that).

Thanks, however dynamic arrays are unfortunately slow. To access a random element, you need a dereference, a multiplication+addition, another dereference, another multiplication+addition. Janice Caron's workaround, when modified to use a struct placed in the data segment, requires only one dereferencing/multiply+adding - while a static array placed in the data segment requires only arithmetics to access.

Also, I was planning to place the array in the uninitialized data segment (I believe it is called BSS in ELF and object files), not the stack - I believe the default stack size for Windows executables to be 256 kB anyway.

P.S. I believe your function can be reduced to this without any significant changes in behavior:

     T[][] ret = new T[][x];
     foreach(ref row;ret)
         row.length = y;

     return ret;

-- 
Best regards,
 Vladimir                          mailto:thecybershadow at gmail.com