Fast multidimensional Arrays

[Daniel Kozak via Digitalmars-d-learn]

Dne 29.8.2016 v 15:57 rikki cattermole via Digitalmars-d-learn napsal(a):

> My bad, fixed:
>
> double[1000][] A, B, C;
>
> void main() {
>         A = new double[1000][1000];
>         B = new double[1000][1000];
>         C = new double[1000][1000];
>
>         import std.conv : to;
>         import std.datetime;
>         import std.stdio : writeln;
>
>         ini(A);
>         ini(B);
>         ini(C);
>
>         auto r = benchmark!run_test(10000);
>         auto res = to!Duration(r[0]);
>         writeln(res);
> }
>
> void run_test() {
>         MatMul(A, B, C);
> }
>
> void ini(T)(T mtx) {
>         foreach(ref v; mtx) {
>                 v = 3.4;
>         }
>
>         foreach(i, v; mtx) {
>                 foreach(j, ref vv; v) {
>                         vv += (i * j) + (0.6 * j);
>                 }
>         }
> }
>
> void MatMul(T)(T A, T B, T C) {
>         foreach(cv; C) {
>                 cv = 0f;
>         }
>
>         foreach(i, cv; C) {
>                 foreach(j, av; A[i]) {
>                         auto bv = B[j];
>                         foreach(k, cvv; cv) {
>                                 cvv += av * bv[k];
>                         }
>                 }
>         }
>
> }

This will not work, you need to add some ref :).

     foreach(i, ref cv; C) {
         foreach(j, av; A[i]) {
             auto bv = B[j];
             foreach(k, ref cvv; cv) {
                 cvv += av * bv[k];
             }
         }
     }