(0.8.0)
A Future represents the return value or uncaught exception from a task, and exposes an API for cancellation.
Example #1 Example showing Future as return value
<?php
$runtime = new \parallel\Runtime;
$future = $runtime->run(function(){
return "World";
});
printf("Hello %s\n", $future->value());
?>The above example will output something similar to:
Hello World
The behaviour of a future also allows it to be used as a simple synchronization point even where the task does not return a value explicitly.
Example #2 Example showing Future as synchronization point
<?php
$runtime = new \parallel\Runtime;
$future = $runtime->run(function(){
echo "in child ";
for ($i = 0; $i < 500; $i++) {
if ($i % 10 == 0) {
echo ".";
}
}
echo " leaving child";
});
$future->value();
echo "\nparent continues\n";
?>The above example will output something similar to:
in child .................................................. leaving child parent continues
<?php
/**
* Sample parallel Runtime/Future processing
* using a generator to produce the list of items to process
*
* Items to process in parallel come from a generator
* It could be anything : e.g fetch a mysql array, a DirectoryIterator...
* Thus the number of items to process in parallel is NOT known in advance
*
* This algorithm attributes items to each parallel thread dynamically
* As soon as a thread has finished working
* It is assigned a new item to process
* until all items are processed (generator closes)
*
* In this example we process 50 items in 5 parallel threads
* It produces output in this form (output changes at each run) :
*
* ThreadId: 1 => Item: 1 (Start)
* ThreadId: 2 => Item: 2 (Start)
* ThreadId: 3 => Item: 3 (Start)
* ThreadId: 4 => Item: 4 (Start)
* ThreadId: 5 => Item: 5 (Start)
* ThreadId: 5 => Item: 5 Sleep: 3s (End)
* ThreadId: 5 => Item: 6 (Start)
* ThreadId: 3 => Item: 3 Sleep: 4s (End)
* ThreadId: 3 => Item: 7 (Start)
* ThreadId: 2 => Item: 2 Sleep: 6s (End)
* ThreadId: 2 => Item: 8 (Start)
* ...
* ThreadId: 4 => Item: 44 Sleep: 6s (End)
* ThreadId: 4 => Item: 49 (Start)
* ThreadId: 3 => Item: 46 Sleep: 5s (End)
* ThreadId: 3 => Item: 50 (Start)
* ThreadId: 2 => Item: 43 Sleep: 9s (End)
* Destroy ThreadId: 2
* ThreadId: 1 => Item: 47 Sleep: 5s (End)
* Destroy ThreadId: 1
* ThreadId: 4 => Item: 49 Sleep: 7s (End)
* Destroy ThreadId: 4
* ThreadId: 5 => Item: 48 Sleep: 10s (End)
* Destroy ThreadId: 5
* ThreadId: 3 => Item: 50 Sleep: 10s (End)
* Destroy ThreadId: 3
*/
// Generate list of items to process with a generator
function generator(int $item_count) {
echo "Item count: $item_count\n";
for ($i=1; $i <= $item_count; $i++) {
yield $i;
}
}
function testConcurrency(int $concurrency, int $max_item_count) {
// Set item_count to a random number so that each run is different
$item_count= rand(1, $max_item_count);
// Create generator
$generator = generator($item_count);
// Function executing in each thread. Have a snap for a random time for example !
// You could make some calculation here or transfer files or whatever...
$producer = function (int $item_id) {
$seconds = rand(1, 10);
sleep($seconds);
return ['item_id' => $item_id, 'sleep_seconds' => $seconds];
};
// Fill up threads with a single future initialized to 'false' value
for ($thread_id = 1; $thread_id <= $concurrency; $thread_id++) {
$threads[$thread_id] = ['runtime' => new \parallel\Runtime(), 'future' => false];
}
// Create infinite loop for the whole processing
while (true) {
// Loop through threads until generator closes and all threads are destroyed
foreach ($threads as $thread_id => &$thread) {
if ($thread['future'] === false and $generator->valid()) {
// Thread is inactive and generator still has values : run something in the thread
$item_id = $generator->current();
$thread['future'] = $thread['runtime']->run($producer, [$item_id]);
echo "ThreadId: $thread_id => Item: $item_id (Start)\n";
$generator->next();
} elseif ($thread['future'] === false) {
// Destroy thread in case generator is closed
echo "Destroy ThreadId: $thread_id\n";
unset($threads[$thread_id]);
} elseif ($thread['future']->done()) {
// Thread finished working. Get result value.
$item = $thread['future']->value();
echo "ThreadId: $thread_id => Item: {$item['item_id']} Sleep: {$item['sleep_seconds']}s (End)\n";
// Thread is ready to run again
$thread['future'] = false;
}
}
// Escape infinite loop when all threads are destroyed
if (empty($threads)) break;
}
}
$concurrency = 5;
$item_count = 50;
testConcurrency($concurrency, $item_count);
?>