这段代码使用的是哪种FFT算法

我在网上找到的，没有评论。

它附带了一个complex .类，基本上模拟了复数及其运算。

我想自己评论一下，但我真的不能确定使用的是哪种算法。我上网发现Cooley-Tukey算法是最普遍的，但我不确定这段代码是否使用了它。

private $dim;
private $p;
private $ind;
private $func;
private $w1;
private $w1i;
private $w2;
public function __construct($dim) {
    $this->dim = $dim;
    $this->p = log($this->dim, 2);
}

public function fft($func) {
    $this->func = $func;
    // Copying func in w1 as a complex.
    for ($i = 0; $i < $this->dim; $i++)
        $this->w1[$i] = new Complex($func[$i], 0);
    $w[0] = new Complex(1, 0);
    $w[1] = new Complex(cos((-2 * M_PI) / $this->dim), sin((-2 * M_PI) / $this->dim));
    for ($i = 2; $i < $this->dim; $i++)
        $w[$i] = Complex::Cmul($w[$i-1], $w[1]);
    return $this->calculate($w);
}
private function calculate($w) {
    $k = 1;
    $ind[0] = 0;
    for ($j = 0; $j < $this->p; $j++) {
        for ($i = 0; $i < $k; $i++) {
            $ind[$i] *= 2;
            $ind[$i+$k] = $ind[$i] + 1;
        }
        $k *= 2;
    }
    for ($i = 0; $i < $this->p; $i++) {
        $indw = 0;
        for ($j = 0; $j < pow(2, $i); $j++) {
            $inf = ($this->dim / pow(2, $i)) * $j;
            $sup = (($this->dim / pow(2, $i)) * ($j+1)) - 1;
            $comp = ($this->dim / pow(2, $i)) / 2;
            for ($k = $inf; $k <= floor($inf+(($sup-$inf)/2)); $k++)
                $this->w2[$k] = Complex::Cadd(Complex::Cmul($this->w1[$k], $w[0]), Complex::Cmul($this->w1[$k+$comp], $w[$ind[$indw]]));    
            $indw++;
            for ($k = floor($inf+(($sup-$inf)/2)+1); $k <= $sup; $k++)
                $this->w2[$k] = Complex::Cadd(Complex::Cmul($this->w1[$k], $w[$ind[$indw]]), Complex::Cmul($this->w1[$k-$comp], $w[0]));
            $indw++;
        }
        for($j = 0; $j < $this->dim; $j++)
            $this->w1[$j] = $this->w2[$j];
    }
    for ($i = 0; $i < $this->dim; $i++)
        $this->w1[$i] = $this->w2[$ind[$i]];
    return $this->w1;
}