test "matmul" {
    const T = i64;
    const M = 3;
    const N = 4;
    const P = 2;

    const A = [M][N]T{
        [_]T{ 1, 2, 1, -2 },
        [_]T{ -1, 3, 2, 4 },
        [_]T{ 0, 1, -1, 0 },
    };

    const B = [N][P]T{
        [_]T{ 1, 2 },
        [_]T{ -2, 1 },
        [_]T{ 3, 0 },
        [_]T{ 0, 1 },
    };

    const actual = matmul(A, B);

    const expected = [M][P]T{
        [_]T{ 0, 2 },
        [_]T{ -1, 5 },
        [_]T{ -5, 1 },
    };

    var m: u64 = 0;
    while (m < M) : (m += 1) {
        std.debug.assert(std.mem.eql(T, actual[m], expected[m]));
    }
}