PHP算法学习（2） 轮训加权算法

<?php

/*
 * 加权轮训算法
 * 
 * 
 * $arr = array(
  array(‘id‘ => ‘A‘, ‘weight‘ => 3),
  array(‘id‘ => ‘B‘, ‘weight‘ => 3),
  array(‘id‘ => ‘C‘, ‘weight‘ => 6),
  array(‘id‘ => ‘D‘, ‘weight‘ => 4),
  array(‘id‘ => ‘E‘, ‘weight‘ => 1),
  );
 * $arr = array(
  array(‘id‘ => ‘192.168.1.1‘, ‘weight‘ => 3),
  array(‘id‘ => ‘192.168.1.1‘, ‘weight‘ => 3),
  array(‘id‘ => ‘192.168.1.1‘, ‘weight‘ => 6),
  array(‘id‘ => ‘192.168.1.1‘, ‘weight‘ => 4),
  array(‘id‘ => ‘192.168.1.1‘, ‘weight‘ => 1),
  );
 */

class ZxWeightedRoundRobin {

    private static $_weightArray = array();
    private static $_i = -1; //代表上一次选择的服务器
    private static $_gcd; //表示集合S中所有服务器权值的最大公约数
    private static $_cw = 0; //当前调度的权值
    private static $_max; //最大元素的值
    private static $_n; //总元素个数

    public function __construct(array $weightArray) {
        self::$_weightArray = $weightArray;
        self::$_gcd = self::getGcd(self::$_weightArray);
    }

    public function getWeight() {
        while (true) {
            self::$_i = ((int) self::$_i + 1) % (int) self::$_n;
            if (self::$_i == 0) {
                self::$_cw = (int) self::$_cw - (int) self::$_gcd;
                if (self::$_cw <= 0) {
                    self::$_cw = (int) self::$_max;
                    if (self::$_cw == 0) {
                        return null;
                    }
                }
            }

            if ((int) (self::$_weightArray[self::$_i][‘weight‘]) >= self::$_cw) {
                return self::$_weightArray[self::$_i];
            }
        }
    }

    //获取最大公约数 Greatest common divisor  最大共同被除数
    private static function getGcd(array $weightArray) {
        if (empty($weightArray)) {
            throw new \Exception(‘数组不能为空‘);
        }
        $weight = [];
        //权重只能为正整数
        foreach ($weightArray as $k => $v) {
            if (!is_int($v[‘weight‘]) || $v[‘weight‘] <= 0) {
                throw new \Exception(‘权限不合法‘);
            }
            $weight[] = $v[‘weight‘];
        }
        $min = min($weight);
        self::$_max = max($weight);
        self::$_n = count($weight);
        //如果最小值是1，最小公约数就必定是1
        if ($min == 1) {
            return 1;
        }
        //如果不是1，就每个元素，循环查询对最小值往下做整除处理，如果全可以整除，如果有一个不能就中断
        for ($i = $min; $i > 1; $i--) {
            foreach ($weight as $k1 => $v1) {
                if ($v1 % $i == 0) {
                    $status = true;
                } else {
                    $status = false;
                    break;
                }
            }
            if ($status) {
                return $i;
            } else {
                return 1;
            }
        }
    }

}

$arr = array(
    array(‘id‘ => ‘A‘, ‘weight‘ => 3),
    array(‘id‘ => ‘B‘, ‘weight‘ => 3),
    array(‘id‘ => ‘C‘, ‘weight‘ => 6),
    array(‘id‘ => ‘D‘, ‘weight‘ => 4),
    array(‘id‘ => ‘E‘, ‘weight‘ => 2),
);
$weight = new ZxWeightedRoundRobin($arr);
$a = 0;
$b = 0;
$c = 0;
$d = 0;
$e = 0;
for ($j = 0; $j < 100; $j++) {
    $weightInfo = $weight->getWeight();
    print_r($weightInfo);
    echo $weightInfo[‘id‘] . ‘----------------------weight:‘ . $weightInfo[‘weight‘] . ‘<br/>‘;
    if ($weightInfo[‘id‘] == ‘A‘) {
        $a++;
    }
    if ($weightInfo[‘id‘] == ‘B‘) {
        $b++;
    }
    if ($weightInfo[‘id‘] == ‘C‘) {
        $c++;
    }
    if ($weightInfo[‘id‘] == ‘D‘) {
        $d++;
    }
    if ($weightInfo[‘id‘] == ‘E‘) {
        $e++;
    }
}
echo ‘A:‘ . $a . ‘<br/>‘;
echo ‘B:‘ . $b . ‘<br/>‘;
echo ‘C:‘ . $c . ‘<br/>‘;
echo ‘D:‘ . $d . ‘<br/>‘;
echo ‘E:‘ . $e . ‘<br/>‘;
exit;