bench.php

<?php

# Benchmark for the cost of returning a new promise from then() for coroutines.
#
#  - composer install
#  - php bench.php
#  - vi vendor/amphp/amp/lib/functions.php # remove 'done' branch --> https://git.io/v7NWW
#  - php bench.php

require __DIR__ . "/vendor/autoload.php";

$start = microtime(1);

Amp\Loop::run(function () {
    for ($i = 0; $i < 300000; $i++) {
        $promise = new React\Promise\Promise(function ($resolve, $reject) {
            $resolve(1);
        });

        yield $promise;
    }
});

print "Completed in " . (microtime(1) - $start) . " seconds." . PHP_EOL;

composer.json

{
    "name": "kelunik/promise-performance",
    "require": {
        "amphp/amp": "^2.0",
        "react/promise": "^2.5"
    },
    "authors": [
        {
            "name": "Niklas Keller",
            "email": "me@kelunik.com"
        }
    ]
}