concurrency

PHP parallel programming tutorial and examples using php/parallel extension

• Comparison between single and multiple waiting queues (at post office...)
• PHP/parallel optimized run examples
• Step by step tutorial with exercises and solutions

How to run examples

• Install Docker

• Run a script e.g simulateQueue.php (may take much time on the first run since the Docker container is being build)

./run.sh -b simulateQueue/main.php

Command options :

• -b Builds container. This option MUST be used on first run ! It is optional afterwards.
• -i [official|frankenphp] Whether to use the offical PHP Docker image or that of FrankenPHP project. Defaults to "official"
• -d <Docker-options> Set specific Docker/run options. Useful to control CPU or memory use by Docker. Defaults to "--cpus=2.0".

Scripts

• simulateQueue : compare single and multiple queues average and max waiting time. The queues are implemented as sequential programs. Multiple simulations ar run in parallel.
• lib/Pool.php : a simple "Pool" class to run any number of tasks in parallel with a defined concurrency. Can be reused in any project !

Tutorial

Example are ordered by difficulty, starting with very easy examples.

Each examples/X (where X stands for the number of the example) can be run with the following command :

./run.sh -b tutorial/example/X/main.php

• 1 : "zzz !", Run two simple tasks in parallel
• 2 : "Molière !" Run many tasks in parallel with arguments
• 3 : "Alice is having a snap !", Future object and return value
• 4 : "Alice and Bob sleep simultaneously", Get Future return value as soon as it completes
• 5 : "multiple sleepers in limited number of rooms", Launch tasks in parallel in a limited number of threads and wait for them to complete
• 6 : "http only !", Parallel download with Guzzle 7
• 7 : "SSH the PHP way ! ", Parallel SSH with SSH2 extension
• 8 : "generic !", Parallel SSH as exec shell command and generic concurrency class
• 9 : "Pong...zzz!", Run two simple tasks in parallel and synchronize them with a channel
• 10 : Single queue parallel simulation
• 11 : Multiple queues parallel simulation
• 12 : Parallel thread launched from a parallel thread
• 42 : Benchmark single and multiple queues in parallel
• 100 : Data-flow : create an adder waiting from two parallel channels to make an addition
• 101 : Prime sieve with daisy-chain filter processes compared to sequential algorithm
• 102 : Fibonacci : Mimics the Go "select" statement with event-loop

Utils (Linux)

• Get number of threads for your process

ps -o thcount <pid>

• Monitor context switches per second : watch "cs" value

vmstat 1

Links

• PHP/parallel repository
• A more complex parallel example: a Web crawler by Joe Watkins aka Krakjoe
• Presentation of PHP/Parallel at the AFUP 2024 forum (French)

Fund php/parallel