mandel pthreads

mandel.md

This is a rather extreme test ... still, was fun ...

[joe@fiji pthreads]$ time php-zts ../php-src/mandrel.php 0 128

real	0m11.441s
user	0m11.386s
sys	0m0.043s
[joe@fiji pthreads]$ time php-zts ../php-src/mandrel.php 1 128

real	0m2.951s
user	0m21.308s
sys	0m0.243s
[joe@fiji pthreads]$ time php-zts ../php-src/mandrel.php 0 256

real	0m19.072s
user	0m19.010s
sys	0m0.044s
[joe@fiji pthreads]$ time php-zts ../php-src/mandrel.php 1 256

real	0m4.786s
user	0m36.023s
sys	0m0.247s

I used as many threads as I have cores, the only sensible number to use ;)

mandel.php

<?php
/*
* requires pthreads, obviously !!
* usage: 
*	php mandel.php 1 128		- run with threads, 128 iterations
*	php mandel.php 0 128		- run without threads, 128 iterations
* Disclaimer: I know nothing about images, code from:
*	http://code.activestate.com/recipes/577680-multi-threaded-mandelbrot-fractal/
*/

class Render extends Thread {
	
	public function __construct(Mandel $mandel, $id, $max, $img) {
		$this->mandel = $mandel;
		$this->id = $id;
		$this->max = $max;
		$this->img = $img;
	}
	
	public function run() {
		$mandel = $this->mandel;
		
		$iterations = $mandel->getIterations();
		$range = range(
			$this->id,
			$mandel->getSum(),
			$this->max);
		$width = $mandel->getWidth();
		$height = $mandel->getHeight();
		$draw = $mandel->getDraw();
		$image = $this->img;
		
		foreach ($range as $pixel) {
			$kx = $pixel % $width;
			$ky = (int) $pixel / $width;
			$a = $draw["xa"] + 
				 $draw["xd"] * $kx / ($width - 1.0);
			$b = $b = $draw["ya"] + 
				 $draw["yd"] * $ky / ($height - 1.0);
			$x = $a;
			$y = $b;
			for ($it = 0; $it < $iterations; $it++) {
				 $x0 = $x * $x - $y * $y + $a;
				 $y = 2.0 * $x * $y + $b;
				 $x = $x0;
				 
				 if ($x * $x + $y * $y > 4) {
				 	$c = imagecolorallocate(
					 		$image, 
					 		($it % 8) * 32, 
					 		(16 - $it % 16) * 16,
					 		($it % 16) * 16);

				 	imagesetpixel(
				 		$image, $kx, $ky, $c);
				 	break;
				 }
			}
		}
	}
	
	protected $mandel;
	protected $id;
	protected $max;
	protected $img;
}

class Mandel extends Stackable {
	
	public function __construct($width, $height, $iterations) {
		$this->width = $width;
		$this->height = $height;
		$this->sum = $this->width * 
					 $this->height;
		$this->iterations = $iterations;
		$this->draw = [
			"xa" => -2,
			"xb" => 1.0,
			"ya" => -1.5,
			"yb" => 1.5,
			"xd" => 1.0 - (-2),
			"yd" => 1.5 - (-1.5)
		];
	}
	
	public function getIterations() { return $this->iterations; }
	public function getDraw()		{ return $this->draw; }
	public function getSum()		{ return $this->sum; }
	public function getWidth()		{ return $this->width; }
	public function getHeight()		{ return $this->height; }
	
	public function createImage() {
		return imagecreatetruecolor(
			$this->width, $this->height);
	}
	
	public function run(){}
	
	protected $width;
	protected $height;
	protected $sum;
	protected $iterations;
	protected $draw;
}

$threaded = isset($argv[1]) ? intval($argv[1]) : 1;
$iterations = isset($argv[2]) ? intval($argv[2]) : 64;

$mandel = new Mandel(1920, 1280, $iterations);
$image   = $mandel->createImage();

$threads = [];							# array of threads
$thread = 0;							# current thread identifier
$max = 8;								# maximum number of threads

while ($thread<$max) {					# create all threads, or not
	$threads[$thread] = new Render(
		$mandel, $thread, $max, $image);
	if (!$threaded) {
		$threads[$thread]->run();
	} else $threads[$thread]->start();
	$thread++;
}

if ($threaded) {
	foreach ($threads as $thread)
		$thread->join();
}

imagepng($image, "mandel.png");			# dump image
?>

If you want to render Larger images, you may get into memory allocation trouble because of the huge amount of items in $range.
Also the statement $image = $this->img; will use a lot of memory.

I would suggest removing L24-L27 and L31
Replacing L33 with:

        for($pixel=$this->id;$pixel<=$mandel->getSum();$pixel+=$this->max) {

And $imagein L49 and L55 with $this->img

With this changes I've made a 15306x10240px @ 8 Threads with 256 Iterations without problems.

https://gist.github.com/krakjoe/9274747#file-mandel-php-L68 should be

class Mandel extends Threaded {