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Date: Tue, 29 Sep 2015 11:36:55 -0400
Message-ID: <CAAyV7nEVmdMR=4QUXrvk9yqtpHwDuUL3Urs7zxTT3a2B0NLG2Q@mail.gmail.com>
To: Thomas Hruska <thruska@cubiclesoft.com>
Cc: Joe Watkins <pthreads@pthreads.org>, =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>, 
	Kalle Sommer Nielsen <kalle@php.net>, Pierre Joye <pierre.php@gmail.com>, Levi Morrison <levim@php.net>, 
	PHP internals <internals@lists.php.net>, "S.A.N" <ua.san.alex@gmail.com>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] async/await - is future reserved words in PHP 7.x?
From: ircmaxell@gmail.com (Anthony Ferrara)

Thomas,

On Tue, Sep 29, 2015 at 11:22 AM, Thomas Hruska <thruska@cubiclesoft.com> wrote:
> On 9/29/2015 6:52 AM, Joe Watkins wrote:
>>
>> We shouldn't reserve words on a whim ...
>>
>> async/await doesn't solve any problems for multithreaded programming, at
>> all ... it solves problems for asynchronous programming, a different
>> concept ... let's not confuse the two ...
>
>
> Actually, it does.  Asynchronous and multithreaded programming are attempts
> at solving the exact same problem:  Simultaneously handling multiple data
> streams in whatever form that takes whether that be network, hard drive,
> random device XYZ, RAM, or even CPU.

Parallelism and concurrency are not the same thing. There are a ton of
resources on this, but I'll point to two specifically, Rob Pike (from
GoLang): https://www.youtube.com/watch?v=cN_DpYBzKso and Joe's own
blog: http://blog.krakjoe.ninja/2015/07/the-universe-is-not-aware.html

> Async/await is both the best of and THE solution to both worlds.

A whole lot of people would argue that. It's not that it's not a good
solution, but it's *A* solution. Each mechanism (event loops,
threading, channels, compiler-driven-concurrency, etc) has its own
pros and cons, and handle different situations better.

A simple example is that raw threads can scale across CPUs, but event
loops typically can't (since it's typically single threaded). That's
not to say it's impossible to write a cross-CPU event loop, but that
requires additional implementation/constraints.

There are such non-trivial tradeoffs to each, that there's no clear
"best" solution to any of it. Async/await is one way. Golang's
channels are another subtly different yet very good way as well.
Another even better way may be to take an approach which is to leave
it to the compiler to figure out what can be made async (though that
may not be strictly possible with PHP in most cases).

Claiming that one technique is the victor, without explicitly stating
the constraints that are required, is not a great idea.

Anthony