Php 我的GAHelloWorld实现中的逻辑有什么问题?
我有一个时间表生成任务,根据,它可以通过遗传算法来解决 我通过谷歌搜索找到了许多非常有用的文献和两个“Hello World!”的例子。到目前为止,我已经尝试将它们翻译成php,并重新封装,使代码可用于我未来的任务 下面是一系列例子的链接(抱歉,最后一个是关于俄语的,但是,这里的代码可能有用) 以下是我的实现:Php 我的GAHelloWorld实现中的逻辑有什么问题?,php,arrays,algorithm,oop,genetic-algorithm,Php,Arrays,Algorithm,Oop,Genetic Algorithm,我有一个时间表生成任务,根据,它可以通过遗传算法来解决 我通过谷歌搜索找到了许多非常有用的文献和两个“Hello World!”的例子。到目前为止,我已经尝试将它们翻译成php,并重新封装,使代码可用于我未来的任务 下面是一系列例子的链接(抱歉,最后一个是关于俄语的,但是,这里的代码可能有用) 以下是我的实现: <?php abstract class Creature { protected $fitness; public functi
<?php
abstract class Creature
{
protected $fitness;
public function __construct()
{
$this->fitness = 0;
}
public function getFitness()
{
return $this->fitness;
}
abstract public function calculateFitness();
public function compareTo($creature)
{
return $this->fitness - $creature->fitness;
}
abstract public function mateWith($creature);
abstract public function mutate();
}
abstract class Population
{
protected $creatures;
protected $generation;
public function __construct()
{
$this->creatures = array();
$this->generation = 1;
$this->populate();
}
public function __destruct()
{
unset($this->creatures);
}
public function get($index)
{
return isset($this->creatures[$index]) ? $this->creatures[$index] : null;
}
public function getCount()
{
return count($this->creatures);
}
public function getGeneration()
{
return $this->generation;
}
abstract protected function populate();
public function sort($order = SORT_ASC)
{
switch($order)
{
case SORT_ASC:
$fn = function($c1, $c2){ return $c1->compareTo($c2); };
break;
case SORT_DESC:
$fn = function($c1, $c2){ return $c2->compareTo($c1); };
break;
default: return false;
}
return usort($this->creatures, $fn);
}
public function select(array $params)
{
$result = false;
if(isset($params['top']))
{
$length = round(abs($this->getCount() * $params['top']) / 100);
$this->creatures = array_slice($this->creatures, 0, $length);
$result = true;
}
if(isset($params['fn']) && is_callable($params['fn']))
{
$this->creatures = array_filter($this->creatures, $params['fn']);
$result = true;
}
return $result;
}
public function breed()
{
$candidates = $this->creatures;
shuffle($candidates);
$candidates = array_chunk($candidates, 2);
$result = 0;
foreach($candidates as &$pair)
{
if(count($pair) < 2)continue;
list($mother, $father) = $pair;
$children = $mother->mateWith($father);
$result += count($children);
$this->creatures = array_merge($this->creatures, $children);
}
$this->generation++;
return $result;
}
}
class HWCreature extends Creature
{
protected $string;
protected function randChar()
{
return chr(rand(0, 255));
}
protected function fill()
{
$length = strlen(Algorithm::TARGET);
for($i = 0; $i < $length; $i++)
{
$this->string .= $this->randChar();
}
}
public function __construct($fill = true)
{
parent::__construct();
$this->string = '';
if(!$fill)return;
$this->fill();
$this->calculateFitness();
}
public function __toString()
{
return $this->string;
}
public function calculateFitness()
{
$length = strlen($this->string);
$target = Algorithm::TARGET;
for($i = 0; $i < $length; $i++)
{
$this->fitness += abs(ord($this->string[$i]) - ord($target[$i]));
}
}
public function mateWith($creature)
{
$length = strlen(Algorithm::TARGET) - 1;
$place = rand(0, $length);
$child1 = new self(false);
$child1->string = substr($this->string, 0, $place) . substr($creature->string, $place);
$child1->mutate();
$child1->calculateFitness();
$child2 = new self(false);
$child2->string = substr($creature->string, 0, $place) . substr($this->string, $place);
$child2->mutate();
$child2->calculateFitness();
return array($child1, $child2);
}
public function mutate()
{
if(rand(1, 100) > Algorithm::MUTATION_RATE)return;
$char = $this->randChar();
$length = strlen(Algorithm::TARGET);
$place = rand(0, $length - 1);
$this->string = substr_replace($this->string, $char, $place, 1);
}
}
class HWPopulation extends Population
{
protected function populate()
{
for($i = 0; $i < Algorithm::POPULATION_SIZE; $i++)
{
$this->creatures[] = new HWCreature();
}
}
}
class Algorithm
{
const POPULATION_SIZE = 100; // 1000 in my original test
const ELITE_RATE = 50; // %
const MUTATION_RATE = 25; // %
const MAX_GENERATIONS = 1000;
const TARGET = 'Hello World!';
protected $population;
public function __construct()
{
$this->population = new HWPopulation();
}
public function __destruct()
{
unset($this->population);
}
public function __invoke()
{
do
{
$generation = $this->population->getGeneration();
$representer = $this->population->get(0);
echo sprintf(
'gen %d > %s',
$generation, $representer
),
'<br>',
PHP_EOL;
if($representer == self::TARGET)break;
$selector = array('top' => self::ELITE_RATE);
$this->population->sort();
$this->population->select($selector);
$this->population->breed();
}
while($generation < self::MAX_GENERATIONS);
}
}
$algorithm = new Algorithm();
$algorithm();
unset($algorithm);
?>
所以,看起来效率非常低。我相信,问题可能在于选择或繁殖策略。。。我完全迷路了
请任何人解释一下,为什么会这样?另外,我只与基因/生物精英群体交配,这是不是做错了什么
任何帮助都将不胜感激。对于调试/测试,至少您可能需要长时间运行该算法,因此您应该在php.ini中增加
max\u execution\u time
的值(或使用该函数)
代码中的术语似乎有些混乱。从非常简短的一瞥来看,你似乎没有实施精英主义。你似乎拥有的是。这样选择父母是错误的吗?它通常是次优的,因为它完全抛弃了较弱的候选者,这些候选者虽然自身不可行,但可能包含可能有助于最终解决方案的遗传物质。在这个简单的例子中,这可能并不重要,但一般来说,您可能会发现一个更有效的方法,例如轮盘赌轮选择。这种策略有利于更强的个体,但允许较弱的候选人被选为父母
若你们想实行精英主义,你们应该将未经修改的精英候选者复制到下一代,然后通过从整个当代(包括精英个体)中选择父母来繁育这一代的其余部分。通过精英主义保留下来的候选人比例应该在5%左右(你可以通过实验找到最佳比例)
其他一些意见:
你能再解释一下输出吗,我是说“HfkkoWotlc!”。上一代的产量相同吗?@AkashdeepSaluja是的。当适合度在8到20之间时,搜索不知何故会停止。结果应该等于string
Hello World代码>。就我而言,一千代人都找不到它。然而,在我作为链接提供的java示例中,50代就足够了。谢谢。我会考虑所有这些。至于最大执行时间,这不是问题,因为我将在后台执行它。不过,以后应该会非常优化。再次感谢您。这是一个非常有用的链接,你在那里提供的。我刚刚改变了配置,适应度函数和排序顺序,正如你所建议的,它在第25代中找到了字符串。
...
gen 739 > HfkkoWotlc!
gen 740 > HfkkoWotlc!
gen 741 > HfkkoWotlc!
gen 742 > HfkkoWotlc!
gen 743 > HfkkoWotlc!
gen 744 > HfkkoWotlc!
gen 745 > HfkkoWotlc!
Fatal error: Maximum execution time of 30 seconds exceeded in {script} on line 126