Multiply Matrices

This algorithm multiplies two given matrices

• C#
• VB.Net
• C
• C++
• PHP

									class Matrix
{
	public $_Matrix;
	public $Rows;
	public $Columns;
}

function MultiplyMatrices($firstMatrix, $secondMatrix)
{
	$mult = array();

	if ($firstMatrix->Columns != $secondMatrix->Rows)
		return new Matrix();

	for ($i = 0; $i < $firstMatrix->Rows; $i++)
		for ($j = 0; $j < $secondMatrix->Columns; $j++)
		{
			$mult[$i][$j] = 0;
		}

	for ($i = 0; $i < $firstMatrix->Rows; $i++)
		for ($j = 0; $j < $secondMatrix->Columns; $j++)
			for ($k = 0; $k < $firstMatrix->Columns; $k++)
			{
				$mult[$i][$j] += $firstMatrix->_Matrix[$i][$k] * $secondMatrix->_Matrix[$k][$j];
			}

	$retVal = new Matrix();
	$retVal->_Matrix = $mult;
	$retVal->Rows = $firstMatrix->Rows;
	$retVal->Columns = $secondMatrix->Columns;
	return $retVal;
}
								

Example

									$m1 = array();
$m1[0][0] = 3;
$m1[0][1] = -2;
$m1[0][2] = 5;
$m1[1][0] = 3;
$m1[1][1] = 0;
$m1[1][2] = 4;

$m2 = array();
$m2[0][0] = 2;
$m2[0][1] = 3;
$m2[1][0] = -9;
$m2[1][1] = 0;
$m2[2][0] = 0;
$m2[2][1] = 4;

$matrix1 = new Matrix();
$matrix1->_Matrix = $m1;
$matrix1->Rows = 2;
$matrix1->Columns = 3;

$matrix2 = new Matrix();
$matrix2->_Matrix = $m2;
$matrix2->Rows = 3;
$matrix2->Columns = 2;

$sumMatrix = MultiplyMatrices($matrix1, $matrix2);
								

Output

									[0][0] = 24
[0][1] = 29
[1][0] = 6
[1][1] = 25