• Jonathan Stephens (62/62) Feb 16 2012 I would like to get some feedback on a language feature I think would be...
• Robert Jacques (2/3) Feb 17 2012 Does std.parallelism fit your needs?

Jonathan Stephens <slashrslashn gmail.com> writes:

I would like to get some feedback on a language feature I think would benefit D.

The feature is simplified "lazy" thread blocks that would considerably
simplify the process of spawning and running new threads.
Multiprocessing is becoming a more-and-more important feature for
programmers as Moore's Law pushes us into a greater number of
processors with only marginal speed improvements.

I think this feature could make it so much simpler to start and stop
threads that many programmers that currently only multiprocess when
necessary would, instead, do it any time they felt their software
could benefit from it.

Anyhow, here's an example of my idea:

import std.stdio;
import core.thread;

void main() {
	runthread {
		Thread.sleep(dur!("msecs")(20));
		writeln("C");
	}
	threadA: runthread {
		Thread.sleep(dur!("msecs")(10));
		writeln("A");
	}

	sync threadA;
	writeln("B");
	sync;
	writeln("End");
}

For this example, the output would always be:
A
B
C
End

Internally, the compiler would convert the runthread blocks into
something more-or-less like this:

import std.stdio;
import core.thread;

void main() {
	void doC() {
		Thread.sleep(dur!("msecs")(10));
		writeln("C");
	}
	Thread threadC = new Thread(&doC);
	threadC.start();

	void doA() {
		writeln("A");
	}
	Thread threadA = new Thread(&doA);
	threadA.start();

	threadA.join(); //sync threadA;
	writeln("B");
	threadC.join(); //sync all threads that haven't been join'd yet
	writeln("End");
}

For something as simple as printing text, the thread overhead isn't
worth it; this is just an example. Imagine instead that you needed to
run several queries against a database while also fetching a remote
URL before using the results from all of those to display something to
the user. This change would make doing those tasks in parallel
trivial.

What are your thoughts? From a high level, does this seem that it
would beneficial? Would it be worth my time to implement this?

- Jon

"Robert Jacques" <sandford jhu.edu> writes:

On Thu, 16 Feb 2012 20:38:37 -0600, Jonathan Stephens <slashrslashn gmail.com>
wrote:
 I would like to get some feedback on a language feature I think would benefit
D.

Does std.parallelism fit your needs?