Re: std.parallelism: How to wait all tasks finished?
On Wednesday, 5 February 2014 at 15:38:14 UTC, Cooler wrote:
On Tuesday, 4 February 2014 at 03:26:04 UTC, Dan Killebrew
wrote:
It seems to me that worker threads will continue as long as
the queue isn't empty. So if a task adds another task to the
pool, some worker will process the newly enqueued task.
No. After taskPool.finish() no way to add new tasks to the
queue. taskPool.put will not add new tasks.
Then perhaps you need to create a new TaskPool (and make sure
that workers add their tasks to the correct task pool), so
that you can wait on the first task pool, then wait on the
second task pool, etc.
auto phase1 = new TaskPool();
//make sure all new tasks are added to phase1
phase1.finish(true);
auto phase2 = new TaskPool();
//make sure all new tasks are added to phase2
phase2.finish(true);
Will not help. I don't know beforehand what tasks will be
created. procData is recursive and it decides create new task or
not.
Something like this? (not tested...)
shared bool more = true;
...
...
...
void procData(){
if(...)
{
taskPool.put(task(procData));
more = true;
}
}
while(true)
{
taskPool.finish(true);
if (!more) break;
else more = false;
}
Re: std.parallelism: How to wait all tasks finished?
On Thursday, 6 February 2014 at 14:52:36 UTC, Cooler wrote:
On Thursday, 6 February 2014 at 14:42:57 UTC, Cooler wrote:
On Thursday, 6 February 2014 at 11:30:17 UTC, Andrea Fontana
wrote:
On Wednesday, 5 February 2014 at 15:38:14 UTC, Cooler wrote:
On Tuesday, 4 February 2014 at 03:26:04 UTC, Dan Killebrew
wrote:
It seems to me that worker threads will continue as long
as the queue isn't empty. So if a task adds another task
to the pool, some worker will process the newly enqueued
task.
No. After taskPool.finish() no way to add new tasks to the
queue. taskPool.put will not add new tasks.
Then perhaps you need to create a new TaskPool (and make
sure that workers add their tasks to the correct task
pool), so that you can wait on the first task pool, then
wait on the second task pool, etc.
auto phase1 = new TaskPool();
//make sure all new tasks are added to phase1
phase1.finish(true);
auto phase2 = new TaskPool();
//make sure all new tasks are added to phase2
phase2.finish(true);
Will not help. I don't know beforehand what tasks will be
created. procData is recursive and it decides create new
task or
not.
Something like this? (not tested...)
shared bool more = true;
...
...
...
void procData(){
if(...)
{
taskPool.put(task(procData));
more = true;
}
}
while(true)
{
taskPool.finish(true);
if (!more) break;
else more = false;
}
It is closer, but after taskPool.finish() all tries to
taskPool.put() will be rejected. Let's me clear example.
import std.stdio, std.parallelism, core.thread;
shared int i;
void procData(){
synchronized ++i;
if(i = 100)
return;
foreach(i; 0 .. 100)
taskPool.put(task(procData)); // New tasks will be
rejected after
// taskPool.finish()
}
void main(){
taskPool.put(task(procData));
Thread.sleep(1.msecs); // The final output of i depends on
duration here
taskPool.finish(true);
writefln(i = %s, i);
}
In the example above the total number of tasks executed
depends on sleep duration.
Forgot to say - I know how to solve the topic problem. My
question is What is the BEST way?.
One of my idea - may be introduce new function, named for
example
wait, that will block until there are working tasks?
What about sync ++taskCount when you put() something and
--taskCount when task is done? And on main while(i 0)
Thread.yield(); ?
Re: std.parallelism: How to wait all tasks finished?
On Thursday, 6 February 2014 at 16:07:51 UTC, Andrea Fontana
wrote:
On Thursday, 6 February 2014 at 14:52:36 UTC, Cooler wrote:
On Thursday, 6 February 2014 at 14:42:57 UTC, Cooler wrote:
On Thursday, 6 February 2014 at 11:30:17 UTC, Andrea Fontana
wrote:
On Wednesday, 5 February 2014 at 15:38:14 UTC, Cooler wrote:
On Tuesday, 4 February 2014 at 03:26:04 UTC, Dan Killebrew
wrote:
It seems to me that worker threads will continue as long
as the queue isn't empty. So if a task adds another task
to the pool, some worker will process the newly enqueued
task.
No. After taskPool.finish() no way to add new tasks to
the queue. taskPool.put will not add new tasks.
Then perhaps you need to create a new TaskPool (and make
sure that workers add their tasks to the correct task
pool), so that you can wait on the first task pool, then
wait on the second task pool, etc.
auto phase1 = new TaskPool();
//make sure all new tasks are added to phase1
phase1.finish(true);
auto phase2 = new TaskPool();
//make sure all new tasks are added to phase2
phase2.finish(true);
Will not help. I don't know beforehand what tasks will be
created. procData is recursive and it decides create new
task or
not.
Something like this? (not tested...)
shared bool more = true;
...
...
...
void procData(){
if(...)
{
taskPool.put(task(procData));
more = true;
}
}
while(true)
{
taskPool.finish(true);
if (!more) break;
else more = false;
}
It is closer, but after taskPool.finish() all tries to
taskPool.put() will be rejected. Let's me clear example.
import std.stdio, std.parallelism, core.thread;
shared int i;
void procData(){
synchronized ++i;
if(i = 100)
return;
foreach(i; 0 .. 100)
taskPool.put(task(procData)); // New tasks will be
rejected after
// taskPool.finish()
}
void main(){
taskPool.put(task(procData));
Thread.sleep(1.msecs); // The final output of i depends on
duration here
taskPool.finish(true);
writefln(i = %s, i);
}
In the example above the total number of tasks executed
depends on sleep duration.
Forgot to say - I know how to solve the topic problem. My
question is What is the BEST way?.
One of my idea - may be introduce new function, named for
example
wait, that will block until there are working tasks?
What about sync ++taskCount when you put() something and
--taskCount when task is done? And on main while(i 0)
Thread.yield(); ?
Something like this:
import std.stdio, std.parallelism, core.thread;
import std.random;
shared size_t taskCount;
shared size_t i;
void procData()
in { synchronized ++i; }
out { synchronized --taskCount; }
body
{
if (i 100)
return;
foreach(i; 0 .. 100)
{
taskPool.put(task(procData));
synchronized ++taskCount;
}
}
void main(){
taskCount = 2;
taskPool.put(task(procData));
taskPool.put(task(procData));
while(taskCount 0)
Thread.yield();
}
Re: std.parallelism: How to wait all tasks finished?
On Mon, 2014-02-03 at 00:00 +, Cooler wrote: I have several tasks. Each task may or may not create another task. What is the best way to wait until all tasks finished? What you are describing here is a classic fork/join architecture. The tasks are structured as a tree with synchronization handled by the sub-nodes. As far as I am aware std.parallelism focuses on data parallelism which is a scatter/gather (aka map/reduce) model of just a single layer. All the code fragments in the thread have, I believe, been predicated on working with a thread pool as an explicit global entity. I think the problems have stemmed from taking this viewpoint. I would suggest following the way the Java fork/join framework (based on Doug Lea's original) works. There is an underlying global thread pool, but the user code uses the fork/join abstraction layer in order to create the tree of synchronization dependencies. In this case instead of working with tasks directly there needs to be a type whose job it is to be a non-leaf node in the tree that handles synchronization whilst nonetheless creating tasks and submitting them to the pool. This is clearly something that could turn into an addition to std.parallelism or be std.forkjoin. Sorry I have no actual code to offer, but the overall design of what is needed is well understood, at least in the Java context. C++ has a long way to go to catch up, as does D. The other thing that then sits on this is lazy stream parallelism, which is what Java 8 is adding to the mix. -- Russel. = Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel.win...@ekiga.net 41 Buckmaster Roadm: +44 7770 465 077 xmpp: rus...@winder.org.uk London SW11 1EN, UK w: www.russel.org.uk skype: russel_winder
Re: std.parallelism: How to wait all tasks finished?
On Wednesday, 5 February 2014 at 15:38:14 UTC, Cooler wrote: Will not help. I don't know beforehand what tasks will be created. procData is recursive and it decides create new task or not. You seem to be saying that you want to be able to wait for all tasks to complete an indefinite number of times, adding more tasks after each one. Why would you want to do that? The queue for the pool is infinitely long, so just keep adding tasks till you have no more tasks to add. Or if you have a progression of types, like all tasks of type A have to be complete before you can start running the tasks of type B, then you should be able to have a separate thread pool for each type.
Re: std.parallelism: How to wait all tasks finished?
It seems to me that worker threads will continue as long as the queue isn't empty. So if a task adds another task to the pool, some worker will process the newly enqueued task. No. After taskPool.finish() no way to add new tasks to the queue. taskPool.put will not add new tasks. Then perhaps you need to create a new TaskPool (and make sure that workers add their tasks to the correct task pool), so that you can wait on the first task pool, then wait on the second task pool, etc. auto phase1 = new TaskPool(); //make sure all new tasks are added to phase1 phase1.finish(true); auto phase2 = new TaskPool(); //make sure all new tasks are added to phase2 phase2.finish(true);
Re: std.parallelism: How to wait all tasks finished?
// Next line will block execution until all tasks already in queue finished. // Almost all what I need, but new tasks will not be started. taskPool.finish(true); } Are you sure TaskPool.finish isn't what you're looking for? Signals worker threads to terminate when the queue becomes empty. It seems to me that worker threads will continue as long as the queue isn't empty. So if a task adds another task to the pool, some worker will process the newly enqueued task.
