The parallel\Channel class

    (0.9.0)

    Unbuffered Channels

    An unbuffered channel will block on calls to parallel\Channel::send() until there is a receiver, and block on calls to parallel\Channel::recv() until there is a sender. This means an unbuffered channel is not only a way to share data among tasks but also a simple method of synchronization.

    An unbuffered channel is the fastest way to share data among tasks, requiring the least copying.

    Buffered Channels

    A buffered channel will not block on calls to parallel\Channel::send() until capacity is reached, calls to parallel\Channel::recv() will block until there is data in the buffer.

    Closures over Channels

    A powerful feature of parallel channels is that they allow the exchange of closures between tasks (and runtimes).

    When a closure is sent over a channel the closure is buffered, it doesn't change the buffering of the channel transmitting the closure, but it does effect the static scope inside the closure: The same closure sent to different runtimes, or the same runtime, will not share their static scope.

    This means that whenever a closure is executed that was transmitted by a channel, static state will be as it was when the closure was buffered.

    Anonymous Channels

    The anonymous channel constructor allows the programmer to avoid assigning names to every channel: parallel will generate a unique name for anonymous channels.

    Class synopsis

    final class parallel\Channel {
    /* Anonymous Constructor */
    public __construct()
    public __construct(int $capacity)
    /* Access */
    public make(string $name): Channel
    public make(string $name, int $capacity): Channel
    public open(string $name): Channel
    /* Sharing */
    public recv(): mixed
    public send(mixed $value): void
    /* Closing */
    public close(): void
    /* Constant for Infinitely Buffered */
    const Infinite;
    }

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    User Contributed Notes 4 notes

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    4
    hdvianna
    4 years ago
    This is an example of using a channel to produce data for consumers. In this example, the producer Runtime instance will send the time in seconds in which the consumers shall sleep.

    <?php

    use parallel\{Runtime, Channel};

    main($argv);

    function     main(array $argv)
    {
    if (    count($argv) !== 3) {
    echo     "Type: hello-parallel.php <number-of-tasks> <maximum-time-of-sleep (in seconds)>" . PHP_EOL;
    echo     "Example: hello-parallel.php 5 3" . PHP_EOL;
    die;
    } else {
    $numberOfTasks = intval($argv[1]);
    $maximumTimeOfSleep = intval($argv[2]);
    $t1 = microtime(true);
    parallelize($numberOfTasks, $maximumTimeOfSleep);
    $endTime = microtime(true) - $t1;
    echo     PHP_EOL."Finished $numberOfTasks task(s) in {$endTime}s".PHP_EOL;
    }
    }

    function     parallelize(int $numberOfTasks, int $maximumTimeOfSleep)
    {
    $channel = new Channel();

    $taskIds = array_map(function () use ($maximumTimeOfSleep) {
    return     $id = uniqid("task::");
    },     range(0, $numberOfTasks - 1));

    $timesToSleep = array_map(function () use ($maximumTimeOfSleep) {
    return     rand(1, $maximumTimeOfSleep);
    },     $taskIds);

    $producer = new Runtime();
    $producerFuture = $producer->run(function (Channel $channel, array $timesToSleep) {
    foreach (    $timesToSleep as $timeToSleep) {
    $channel->send($timeToSleep);
    }
    }, [    $channel, $timesToSleep]);

    $consumerFutures = array_map(function (string $id) use ($channel) {
    $runtime = new Runtime();
    return     $runtime->run(function (string $id, Channel $channel) {
    $timeToSleep = $channel->recv();
    echo     "Hello from $id. I will sleep for $timeToSleep second(s).".PHP_EOL;
    sleep($timeToSleep);
    echo     "$id slept for $timeToSleep second(s).".PHP_EOL;
    return     $timeToSleep;
    }, [    $id, $channel]);
    },     $taskIds);

    wait($consumerFutures);
    wait([$producerFuture]);
    }

    function     wait(array $futures)
    {
    return     array_map(function ($future) {
    return     $future->value();
    },     $futures);
    }
    up
    2
    rustysun
    4 years ago
    an example used unbuffered channel.
    <?php

    use parallel\{Channel,Runtime};

    $sum=function(array $a, Channel $ch) {
    $sum=0;
    foreach (    $a as $v) {
    $sum+=$v;
    }
    $ch->send($sum);
    };
    try {
    $a=[7, 2, 8, 1, 4, 0, 9, 10];
    //unbuffered channel
    $runtime=new Runtime;
    $ch2=new Channel;
    $runtime->run($sum, [array_slice($a, 0, $num), $ch2]);
    $runtime->run($sum, [array_slice($a, $num), $ch2]);
    //receive from channel
    $x=$ch2->recv();
    $y=$ch2->recv();
    $ch2->close();
    echo     "\nch2:", $x, "\t", $y, "\t", $x + $y, "\n";
    } catch(    Error $err) {
    echo     "\nError:", $err->getMessage();
    } catch(    Exception $e) {
    echo     "\nException:", $e->getMessage();
    }

    //output
    //ch2:18 23 41
    up
    2
    gam6itko
    2 years ago
    <?php

    // the very weird way to calculate factorial ^_^
    // we create one thread and synching them with buffered channel
    // at fact only one thread is executing at the time

    use parallel\{Channel, Future, Runtime};

    for (    $n = 0; $n <= 10; $n++) {
    echo     "!$n = " . factorial($n) . PHP_EOL;
    }

    /**
    * Creates $n threads.
    */
    function factorial(int $n): int
    {
    // buffered channel - using for sync threads ^_^
    $channel = new Channel(1);
    $futureList = [];
    for (    $i = 2; $i <= $n; $i++) {
    $runtime = new Runtime();
    $futureList[] = $runtime->run(
    static function (    Channel $channel, $multiplier): void {
    $f = $channel->recv();
    $channel->send($f * $multiplier);
    },
    [    $channel, $i]
    );
    }

    $channel->send(1);

    // waiting until all threads are done
    do {
    $allDone = array_reduce(
    $futureList,
    function (    bool $c, Future $future): bool {

    return     $c && $future->done();
    },
    true
    );
    } while (    false === $allDone);

    return     $channel->recv();
    }

    // output:
    // !0 = 1
    // !1 = 1
    // !2 = 2
    // !3 = 6
    // !4 = 24
    // !5 = 120
    // !6 = 720
    // !7 = 5040
    // !8 = 40320
    // !9 = 362880
    // !10 = 3628800
    up
    1
    rustysun
    4 years ago
    <?php
    use parallel\Channel;

    function     sum(array $a, Channel $ch) {
    $sum=0;
    foreach (    $a as $v) {
    $sum+=$v;
    }
    $ch->send($sum);
    }

    try {
    $a=[7, 2, 8, 1, 4, 0, 9, 10];
    $ch1=Channel::make('sum', 2);
    $ch2=new Channel;
    $num=count($a) / 2;
    sum(array_slice($a, 0, $num), $ch1);
    sum(array_slice($a, $num), $ch1);

    //receive from channel
    $x=$ch1->recv();
    $y=$ch1->recv();
    $ch1->close();
    echo     "\nch1:", $x, "\t", $y, "\t", $x + $y, "\n";
    } catch(    Error $err) {
    echo     "\nError:", $err->getMessage();
    } catch(    Exception $e) {
    echo     "\nException:", $e->getMessage();
    }
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