PHP学习笔记：科学计算与数值模拟

function matrixMultiplication($matrix1, $matrix2) {
    $rows1 = count($matrix1);
    $columns1 = count($matrix1[0]);
    $columns2 = count($matrix2[0]);

    $result = array();
    for($i=0; $i<$rows1; $i++) {
        for($j=0; $j<$columns2; $j++) {
            $sum = 0;
            for($k=0; $k<$columns1; $k++) {
                $sum += $matrix1[$i][$k] * $matrix2[$k][$j];
            }
            $result[$i][$j] = $sum;
        }
    }
    return $result;
}

$matrix1 = array(array(1, 2, 3), 
                 array(4, 5, 6));
$matrix2 = array(array(7, 8), 
                 array(9, 10), 
                 array(11, 12));

$result = matrixMultiplication($matrix1, $matrix2);
print_r($result);

function f($x) {
    return sin($x);
}

function numericalIntegration($a, $b, $n) {
    $h = ($b - $a) / $n;
    $sum = 0;
    for($i=0; $i<=$n; $i++) {
        $x = $a + $i*$h;
        $sum += f($x);
    }
    return $h * $sum;
}

$result = numericalIntegration(0, pi(), 100);
echo $result;

function randomWalk($steps) {
    $x = 0;
    for($i=0; $i<$steps; $i++) {
        $random = mt_rand(0, 1);
        if($random == 0) {
            $x -= 1;
        } else {
            $x += 1;
        }
    }
    return $x;
}

$result = randomWalk(100);
echo $result;