Re: parallelFuture
== Quote from Tim Matthews (tim.matthe...@gmail.com)'s article > dsimcha wrote: > > For now, parallelFuture was designed with a single producer, multiple worker > > model. Absolutely no attempt was made to allow for tasks running in the > > task pool > > to themselves submit jobs to the same task pool, because it would have made > > things > > more complicated and I couldn't think of any use cases. > like recursion a function is gona need to call another function, a > thread needs to be able to spawn threads and task should be able to > create new tasks. Making newly spawned tasks stay on the same thread is > good optimization. This shouldn't need a specific use case. > > I designed the lib with > > the types of use cases I encounter in my work in mind. (mathy, pure > > throughput > > oriented computing on large, embarrassingly parallel problems.) If someone > > comes > > up with a compelling use case, though, I'd certainly consider adding such > > abilities provided they don't interfere with performance or API simplicity > > for the > > more common cases. > > > > To make this discussion simple, let's define F1 as a future/task submitted > > by the > > main producer thread, and F2 as a task/future submitted by F1. The queue > > is (for > > now) strictly FIFO, except that if you have a pointer to the Task/Future > > object > > you can steal a job. When F1 submits F2 to the queue, F2 goes to the back > > of the > > queue like anything else. This means when F1 waits on F2, it is possible > > to have > > a cyclical dependency (F1 waiting on F2, F2 waiting for a worker thread > > populated > > by F1). This is mitigated by work stealing (F1 may just steal F2 and do it > > in its > > own thread). > I don't like that ^ idea of simple discussion with the many F1 and F2 > all over the place. I hope this video can help visualize some ideas: > http://channel9.msdn.com/pdc2008/TL26/ > > > > In parallel map and foreach, I should probably document this, but for now > > it's > > undefined behavior for the mapping function or parallel foreach loop body to > > submit jobs to the task pool and wait on them, and in practice will likely > > result > > in deadlocks. > You want to document that as undefined behavior? It can be made to work. Ok, I thought of my use case and an easy fix. It will probably be fixed soon.
Re: parallelFuture
dsimcha wrote: For now, parallelFuture was designed with a single producer, multiple worker model. Absolutely no attempt was made to allow for tasks running in the task pool to themselves submit jobs to the same task pool, because it would have made things more complicated and I couldn't think of any use cases. like recursion a function is gona need to call another function, a thread needs to be able to spawn threads and task should be able to create new tasks. Making newly spawned tasks stay on the same thread is good optimization. This shouldn't need a specific use case. I designed the lib with the types of use cases I encounter in my work in mind. (mathy, pure throughput oriented computing on large, embarrassingly parallel problems.) If someone comes up with a compelling use case, though, I'd certainly consider adding such abilities provided they don't interfere with performance or API simplicity for the more common cases. To make this discussion simple, let's define F1 as a future/task submitted by the main producer thread, and F2 as a task/future submitted by F1. The queue is (for now) strictly FIFO, except that if you have a pointer to the Task/Future object you can steal a job. When F1 submits F2 to the queue, F2 goes to the back of the queue like anything else. This means when F1 waits on F2, it is possible to have a cyclical dependency (F1 waiting on F2, F2 waiting for a worker thread populated by F1). This is mitigated by work stealing (F1 may just steal F2 and do it in its own thread). I don't like that ^ idea of simple discussion with the many F1 and F2 all over the place. I hope this video can help visualize some ideas: http://channel9.msdn.com/pdc2008/TL26/ In parallel map and foreach, I should probably document this, but for now it's undefined behavior for the mapping function or parallel foreach loop body to submit jobs to the task pool and wait on them, and in practice will likely result in deadlocks. You want to document that as undefined behavior? It can be made to work.
Re: parallelFuture
dsimcha wrote:
== Quote from Charles Hixson (charleshi...@earthlink.net)'s article
dsimcha wrote:
I've created an alpha release of parallelFuture, a high-level parallelization
library for D2. Right now, it has a task pool, futures, parallel foreach, and
parallel map.
Here's the (IMHO) coolest example:
auto pool = new ThreadPool();
// Assuming we have a function isPrime(), print all
// prime numbers from 0 to uint.max, testing for primeness
// in parallel.
auto myRange = iota(0, uint.max);
foreach(num; pool.parallel(myRange)) {
if(isPrime(num)) {
synchronized writeln(num);
}
}
The interface is there and it seems to work, although it has not been
extensively stress tested yet. Some of the implementation details could
admittedly use some cleaning up, and I would appreciate help from some
threading gurus on improving my queue (right now it's a naive synchronized
singly-linked list) and getting condition mutexes to work properly. (Right
now, I'm using atomic polling followed by sleeping for 1 millisecond in a lot
of places. It's a kludge, but it seems to work reasonably well in practice.)
The code is at:
http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
The docs are at:
http://cis.jhu.edu/~dsimcha/parallelFuture.html
If you can easily do it, it would be nice to be able to have the threads
able to communicate with each other. Something along the lines of both
broadcast messages and 1:1 exchanges. A very rough sketch of a possible
use:
Task[] tasks = Task.who_is_waiting;
foreach (auto task; tasks)
{ if (task.process(something) )
{ task.markDone(true); }
}
I see "something" as being an Object that would need to implement an
interface to carry some identifying information, so when a task received
it it could determine what to do with it (with "reject processing" being
an option). I think the rest is pretty clear.
OTOH, this comment was just to demonstrate the kind of communication
between tasks that I'm talking about. Static methods for broadcast
communication and instance methods for 1:1 communication. With
safeties, so when a task completes before it gets your message, you
aren't left talking to a null pointer. Cleanup would need to be managed
by the original thread that created the tasks. It would need to be able
to send a broadcast "now closing task xxx signal" to all threads.
Threads maintaining a list of tasks would need to scan through them and
remove any references to that task.
Maybe this is getting to complicated, but it would certainly be useful.
In the past interthread communication is the main problem that's kept
me from using them.
I'll think about this and see if I can work something like this in, but I need
real-world use cases. I do bioinformatics work, which basically means
large-scale
data mining, embarrassingly parallel problems and very CPU-bound work. The use
cases I had in mind were mostly the "use every core I have to do something
embarrassingly parallel" kind. The goal was to make these use cases as dead
simple as possible.
Whatever use cases you have in mind, I'm apparently not familiar with them. If
I'm to improve this lib to handle use cases other than the pure
throughput-oriented parallelization of embarrassingly parallel tasks that I had
in
mind, I need to understand use cases from other fields.
It's basically a simplified form of message passing, and useful for
general processing in the context of multiple cores. If you wanted to
implement, say, Smalltalk or Objective-C you could use this to allow
their calls to proceed in parallel. My particular interest is based on
AI. I'm not talking about neural-nets, as that, I think, would incur
too much overhead if implemented with even this kind of simplified
message passing, but one where several "dumb" processes are continually
running in the background and sending messages whenever they detect
something interesting. (So it would also be useful if the tasks could
be assigned an adjustable priority.)
The kind of system I'm envisioning should be able to adjust to a
variable number of processors...even variable while the program is
running. (Yeah, that's not what we're talking about here. I'm talking
about the higher level design.)
Erlang can probably do what I want, but it's incredibly slow. In tests
I've run it's come out even slower than Ruby, which is slower than
Python. Currently my choice is between D and Java. with a preference
for D. Java has the libraries, but D is a better design fit with what I
want to do.
(I can't give detailed specifics, because I haven't yet done any
programming of that part of the process. But the rough design calls for
lots of small modules with a coordinator that manages them. I don't
like having the coordinator be so central, but every threading model
I've seen has a central controller. I'd really rather do something more
like Linux/Unix daemons (see the Pandemonium paper, whic
Re: parallelFuture
== Quote from Charles Hixson (charleshi...@earthlink.net)'s article
> dsimcha wrote:
> > I've created an alpha release of parallelFuture, a high-level
> > parallelization
> > library for D2. Right now, it has a task pool, futures, parallel foreach,
> > and
> > parallel map.
> >
> > Here's the (IMHO) coolest example:
> >
> > auto pool = new ThreadPool();
> >
> > // Assuming we have a function isPrime(), print all
> > // prime numbers from 0 to uint.max, testing for primeness
> > // in parallel.
> > auto myRange = iota(0, uint.max);
> > foreach(num; pool.parallel(myRange)) {
> > if(isPrime(num)) {
> > synchronized writeln(num);
> > }
> > }
> >
> > The interface is there and it seems to work, although it has not been
> > extensively stress tested yet. Some of the implementation details could
> > admittedly use some cleaning up, and I would appreciate help from some
> > threading gurus on improving my queue (right now it's a naive synchronized
> > singly-linked list) and getting condition mutexes to work properly. (Right
> > now, I'm using atomic polling followed by sleeping for 1 millisecond in a
> > lot
> > of places. It's a kludge, but it seems to work reasonably well in
> > practice.)
> >
> > The code is at:
> >
> > http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
> >
> > The docs are at:
> >
> > http://cis.jhu.edu/~dsimcha/parallelFuture.html
> If you can easily do it, it would be nice to be able to have the threads
> able to communicate with each other. Something along the lines of both
> broadcast messages and 1:1 exchanges. A very rough sketch of a possible
> use:
> Task[] tasks = Task.who_is_waiting;
> foreach (auto task; tasks)
> { if (task.process(something) )
> { task.markDone(true); }
> }
> I see "something" as being an Object that would need to implement an
> interface to carry some identifying information, so when a task received
> it it could determine what to do with it (with "reject processing" being
> an option). I think the rest is pretty clear.
> OTOH, this comment was just to demonstrate the kind of communication
> between tasks that I'm talking about. Static methods for broadcast
> communication and instance methods for 1:1 communication. With
> safeties, so when a task completes before it gets your message, you
> aren't left talking to a null pointer. Cleanup would need to be managed
> by the original thread that created the tasks. It would need to be able
> to send a broadcast "now closing task xxx signal" to all threads.
> Threads maintaining a list of tasks would need to scan through them and
> remove any references to that task.
> Maybe this is getting to complicated, but it would certainly be useful.
> In the past interthread communication is the main problem that's kept
> me from using them.
I'll think about this and see if I can work something like this in, but I need
real-world use cases. I do bioinformatics work, which basically means
large-scale
data mining, embarrassingly parallel problems and very CPU-bound work. The use
cases I had in mind were mostly the "use every core I have to do something
embarrassingly parallel" kind. The goal was to make these use cases as dead
simple as possible.
Whatever use cases you have in mind, I'm apparently not familiar with them. If
I'm to improve this lib to handle use cases other than the pure
throughput-oriented parallelization of embarrassingly parallel tasks that I had
in
mind, I need to understand use cases from other fields.
Re: parallelFuture
dsimcha wrote:
I've created an alpha release of parallelFuture, a high-level parallelization
library for D2. Right now, it has a task pool, futures, parallel foreach, and
parallel map.
Here's the (IMHO) coolest example:
auto pool = new ThreadPool();
// Assuming we have a function isPrime(), print all
// prime numbers from 0 to uint.max, testing for primeness
// in parallel.
auto myRange = iota(0, uint.max);
foreach(num; pool.parallel(myRange)) {
if(isPrime(num)) {
synchronized writeln(num);
}
}
The interface is there and it seems to work, although it has not been
extensively stress tested yet. Some of the implementation details could
admittedly use some cleaning up, and I would appreciate help from some
threading gurus on improving my queue (right now it's a naive synchronized
singly-linked list) and getting condition mutexes to work properly. (Right
now, I'm using atomic polling followed by sleeping for 1 millisecond in a lot
of places. It's a kludge, but it seems to work reasonably well in practice.)
The code is at:
http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
The docs are at:
http://cis.jhu.edu/~dsimcha/parallelFuture.html
If you can easily do it, it would be nice to be able to have the threads
able to communicate with each other. Something along the lines of both
broadcast messages and 1:1 exchanges. A very rough sketch of a possible
use:
Task[] tasks = Task.who_is_waiting;
foreach (auto task; tasks)
{ if (task.process(something) )
{ task.markDone(true); }
}
I see "something" as being an Object that would need to implement an
interface to carry some identifying information, so when a task received
it it could determine what to do with it (with "reject processing" being
an option). I think the rest is pretty clear.
OTOH, this comment was just to demonstrate the kind of communication
between tasks that I'm talking about. Static methods for broadcast
communication and instance methods for 1:1 communication. With
safeties, so when a task completes before it gets your message, you
aren't left talking to a null pointer. Cleanup would need to be managed
by the original thread that created the tasks. It would need to be able
to send a broadcast "now closing task xxx signal" to all threads.
Threads maintaining a list of tasks would need to scan through them and
remove any references to that task.
Maybe this is getting to complicated, but it would certainly be useful.
In the past interthread communication is the main problem that's kept
me from using them.
Re: parallelFuture
== Quote from Tim Matthews (tim.matthe...@gmail.com)'s article
> dsimcha wrote:
> > I've created an alpha release of parallelFuture, a high-level
> > parallelization
> > library for D2. Right now, it has a task pool, futures, parallel foreach,
> > and
> > parallel map.
> >
> > Here's the (IMHO) coolest example:
> >
> > auto pool = new ThreadPool();
> >
> > // Assuming we have a function isPrime(), print all
> > // prime numbers from 0 to uint.max, testing for primeness
> > // in parallel.
> > auto myRange = iota(0, uint.max);
> > foreach(num; pool.parallel(myRange)) {
> > if(isPrime(num)) {
> > synchronized writeln(num);
> > }
> > }
> >
> > The interface is there and it seems to work, although it has not been
> > extensively stress tested yet. Some of the implementation details could
> > admittedly use some cleaning up, and I would appreciate help from some
> > threading gurus on improving my queue (right now it's a naive synchronized
> > singly-linked list) and getting condition mutexes to work properly. (Right
> > now, I'm using atomic polling followed by sleeping for 1 millisecond in a
> > lot
> > of places. It's a kludge, but it seems to work reasonably well in
> > practice.)
> >
> > The code is at:
> >
> > http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
> >
> > The docs are at:
> >
> > http://cis.jhu.edu/~dsimcha/parallelFuture.html
> Nice. About the tasks:
> In .Net a worker thread is created for each cpu core. Each worker thread
> has its own local queue of tasks which it initially retrieves from the
> global queue but if the tasks creates new tasks it adds to its local
> queue directly for less contention. When it finishes completing a task
> it takes the next from the back of its local queue to take advantage of
> cache (like a stack). The tasks at the front of the queue can be stolen
> from another worker thread if its local queue and the global queue are
> both empty to maximize cpu usage.
> Also the task's wait for complete is only considered complete if all of
> the tasks it created too are complete (kinda like recursion).
> What is the implementation or plans like for this.
For now, parallelFuture was designed with a single producer, multiple worker
model. Absolutely no attempt was made to allow for tasks running in the task
pool
to themselves submit jobs to the same task pool, because it would have made
things
more complicated and I couldn't think of any use cases. I designed the lib with
the types of use cases I encounter in my work in mind. (mathy, pure throughput
oriented computing on large, embarrassingly parallel problems.) If someone
comes
up with a compelling use case, though, I'd certainly consider adding such
abilities provided they don't interfere with performance or API simplicity for
the
more common cases.
To make this discussion simple, let's define F1 as a future/task submitted by
the
main producer thread, and F2 as a task/future submitted by F1. The queue is
(for
now) strictly FIFO, except that if you have a pointer to the Task/Future object
you can steal a job. When F1 submits F2 to the queue, F2 goes to the back of
the
queue like anything else. This means when F1 waits on F2, it is possible to
have
a cyclical dependency (F1 waiting on F2, F2 waiting for a worker thread
populated
by F1). This is mitigated by work stealing (F1 may just steal F2 and do it in
its
own thread).
In parallel map and foreach, I should probably document this, but for now it's
undefined behavior for the mapping function or parallel foreach loop body to
submit jobs to the task pool and wait on them, and in practice will likely
result
in deadlocks.
Re: parallelFuture
== Quote from Lars T. Kyllingstad (pub...@kyllingen.nospamnet)'s article > Is there some particular reason why you have capitalised the F in the > file name, but not in the module name? > -Lars This is called the effects of being in hack mode late at night. I guess the convention is all lower case.
Re: parallelFuture
dsimcha wrote:
I've created an alpha release of parallelFuture, a high-level parallelization
library for D2. Right now, it has a task pool, futures, parallel foreach, and
parallel map.
Here's the (IMHO) coolest example:
auto pool = new ThreadPool();
// Assuming we have a function isPrime(), print all
// prime numbers from 0 to uint.max, testing for primeness
// in parallel.
auto myRange = iota(0, uint.max);
foreach(num; pool.parallel(myRange)) {
if(isPrime(num)) {
synchronized writeln(num);
}
}
The interface is there and it seems to work, although it has not been
extensively stress tested yet. Some of the implementation details could
admittedly use some cleaning up, and I would appreciate help from some
threading gurus on improving my queue (right now it's a naive synchronized
singly-linked list) and getting condition mutexes to work properly. (Right
now, I'm using atomic polling followed by sleeping for 1 millisecond in a lot
of places. It's a kludge, but it seems to work reasonably well in practice.)
The code is at:
http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
The docs are at:
http://cis.jhu.edu/~dsimcha/parallelFuture.html
Very nice! Parallelisation for us ordinary folks. :) I tried your
isPrime example, which was very cool. I can't wait to try the library in
a real application.
I often have a situation where I have a set of grid points, and I do
(mostly) separate calculations on each grid point. Your library should
allow me to do calculations on several grid points in parallel, with
minimal changes to my code.
Is there some particular reason why you have capitalised the F in the
file name, but not in the module name?
-Lars
Re: parallelFuture
== Quote from dsimcha (dsim...@yahoo.com)'s article
> I've created an alpha release of parallelFuture, a high-level parallelization
> library for D2. Right now, it has a task pool, futures, parallel foreach, and
> parallel map.
> Here's the (IMHO) coolest example:
> auto pool = new ThreadPool();
> // Assuming we have a function isPrime(), print all
> // prime numbers from 0 to uint.max, testing for primeness
> // in parallel.
> auto myRange = iota(0, uint.max);
> foreach(num; pool.parallel(myRange)) {
> if(isPrime(num)) {
> synchronized writeln(num);
> }
> }
> The interface is there and it seems to work, although it has not been
> extensively stress tested yet. Some of the implementation details could
> admittedly use some cleaning up, and I would appreciate help from some
> threading gurus on improving my queue (right now it's a naive synchronized
> singly-linked list) and getting condition mutexes to work properly. (Right
> now, I'm using atomic polling followed by sleeping for 1 millisecond in a lot
> of places. It's a kludge, but it seems to work reasonably well in practice.)
> The code is at:
> http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d
> The docs are at:
> http://cis.jhu.edu/~dsimcha/parallelFuture.html
Very good!
