_Title "MatMul"

$Console:Only

_Dest _Console



Dim As Double a(3, 3), b(3, 3), c(3, 3), d(3, 3)

Dim As Long i



a(0, 0) = 1#: a(0, 1) = 1#: a(0, 2) = 1#: a(0, 3) = 1#

a(1, 0) = 2#: a(1, 1) = 4#: a(1, 2) = 8#: a(1, 3) = 16#

a(2, 0) = 3#: a(2, 1) = 9#: a(2, 2) = 27#: a(2, 3) = 81#

a(3, 0) = 4#: a(3, 1) = 16#: a(3, 2) = 64#: a(3, 3) = 256#



'b() = Inverse of a()

b(0, 0) = 4#: b(0, 1) = -3#: b(0, 2) = 4 / 3#: b(0, 3) = -1 / 4#

b(1, 0) = -13 / 3#: b(1, 1) = 19 / 4#: b(1, 2) = -7 / 3#: b(1, 3) = 11 / 24#

b(2, 0) = 3 / 2#: b(2, 1) = -2#: b(2, 2) = 7 / 6#: b(2, 3) = -1 / 4#

b(3, 0) = -1 / 6#: b(3, 1) = 1 / 4#: b(3, 2) = -1 / 6#: b(3, 3) = 1 / 24#



MatMul d(), a(), a()

MatMul c(), d(), b()

printm c()

Print

For i = 1 To 4

    MatMul d(), c(), c()

    MatMul c(), d(), b()

    printm c()

    Print

Next



Sub MatMul (ans() As Double, a() As Double, b() As Double)

    Dim As Long i, j, k, n, m, p

    If (UBound(a, 2) = UBound(b)) Then 'if valid dims

        n = UBound(a, 2)

        m = UBound(a)

        p = UBound(b, 2)



        For i = 0 To m

            For j = 0 To p

                For k = 0 To n

                    ans(i, j) = 0

        Next k, j, i



        For i = 0 To m

            For j = 0 To p

                For k = 0 To n

                    ans(i, j) = ans(i, j) + (a(i, k) * b(k, j))

        Next k, j, i

    Else

        Print "invalid dimensions"

    End If

End Sub



Sub printm (a() As Double)

    Dim As Long i, j, m, p

    m = UBound(a)

    p = UBound(a, 2)

    For i = 0 To m

        For j = 0 To p

            Print Using "####.##############"; a(i, j);

        Next j

        Print

    Next i

End Sub