Matrix multiplication: Difference between revisions

===Alternative version===

All array sizes are verified at compile-time (and no matrix is copied), same output:

<lang d>import std.stdio, std.string, std.conv, std.numeric,

std.array, std.algorithm, std.traits;

template TMMul(M1, M2) { // helper

alias Unqual!(typeof(M1[0][0]))[M2[0].length][M1.length] TMMul;

}

void matrixMul(T, T2, size_t k, size_t m, size_t n)

(const ref T[m][k] A, const ref T[n][m] B,

/*out*/ ref T2[n][k] result) pure nothrow

if (is(T2 == Unqual!T)) {

T2[m] aux;

foreach (j; 0 .. n) {

foreach (k, row; B)

aux[k] = row[j];

foreach (i, ai; A)

result[i][j] = dotProduct(ai, aux);

}

}

string prettyPrint(T, size_t m, size_t n)(const ref T[m][n] M) {

return "[" ~ array(map!text(M[])).join(",\n ") ~ "]";

}

void main() {

const int[2][3] a = [[1, 2], [3, 4], [3, 6]];

const int[3][2] b = [[-3, -8, 3,], [-2, 1, 4]];

writeln("A =\n", prettyPrint(a), "\n");

writeln("B =\n", prettyPrint(b), "\n");

TMMul!(typeof(a), typeof(b)) result; // = void;

matrixMul(a, b, result);

writeln("A * B =\n", prettyPrint(result));

}</lang>