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digitalmars.D - Concurrency

reply janderson <askme me.com> writes:
Given that the world of PC are heading down the path of muti-cpus:

What features does D supply to take advantage of concurrency, over an 
above what can be accomplished though C++ today?

How could the language be improved to be better at concurrency problems 
then other languages?

(You'll not that I left out the word threading as that is only one form 
of concurrency programming).

-
I'm just thinking that, perhaps if concurrency is handled well enough in 
D, it can catch the wave of parallel programming that is on the horizon.
Dec 10 2006
next sibling parent Sean Kelly <sean f4.ca> writes:
janderson wrote:

 Given that the world of PC are heading down the path of muti-cpus:
 
 What features does D supply to take advantage of concurrency, over an 
 above what can be accomplished though C++ today?


A definition of 'volatile' that works.  I'd say more, but "can be 
accomplished" is a pretty broad category.


 How could the language be improved to be better at concurrency problems 
 then other languages?


Improved support for advanced concurrency features.  I've seen a test 
copy of CSP for D, which is a nice start.  And futures wouldn't be very 
difficult to write in library code.  Really, I think it comes down to 
finding simpler ways to break up the traditionally sequential nature of 
imperative code.  A good bit of work still needs to be done here even at 
the research level, as I haven't seen any solution yet that's without 
problems.  Oh, software transactional memory might be an interesting 
experiment as well.


 I'm just thinking that, perhaps if concurrency is handled well enough in 
 D, it can catch the wave of parallel programming that is on the horizon.


I'd be surprised if it didn't.


Sean
Dec 10 2006
prev sibling next sibling parent reply vtp <vanh dslextreme.com> writes:
janderson Wrote:


 Given that the world of PC are heading down the path of muti-cpus:
 
 What features does D supply to take advantage of concurrency, over an 
 above what can be accomplished though C++ today?
 
 How could the language be improved to be better at concurrency problems 
 then other languages?
 
 (You'll not that I left out the word threading as that is only one form 
 of concurrency programming).
 
 -
 I'm just thinking that, perhaps if concurrency is handled well enough in 
 D, it can catch the wave of parallel programming that is on the horizon.


D should be the language of choice when it comes to concurrency. This the
window of opportunity for D. Since none of the currently "popular" languages
speaks concurrency fluently.
Dec 12 2006
parent renoX <renosky free.fr> writes:
vtp (vanh dslextreme.com) 	2006/12/12 17:53

janderson Wrote:
 I'm just thinking that, perhaps if concurrency is handled well enough in
 D, it can catch the wave of parallel programming that is on the horizon.


D should be the language of choice when it comes to concurrency. This the window


of opportunity for D. Since none of the currently "popular" languages

speaks concurrency fluently.


That's the correct timeperiod sure, but the problem is that the 'concurrency'
topic is far from being settled, there are so many ways to treat it: threading
and
locks (don't compose), STM (still a research topic and not a complete solution:
it
cannot handle side-effect), like in the Concur project active object waiting for
future events (the mapping of "future thread" to real thread doesn't seem
obvious
to me to get good performances), CSP, etc.

renoX
Dec 13 2006
prev sibling parent reply Graham St Jack <grahams acres.com.au> writes:
janderson wrote:

 Given that the world of PC are heading down the path of muti-cpus:
 
 What features does D supply to take advantage of concurrency, over an 
 above what can be accomplished though C++ today?
 
 How could the language be improved to be better at concurrency problems 
 then other languages?
 
 (You'll not that I left out the word threading as that is only one form 
 of concurrency programming).
 
 -
 I'm just thinking that, perhaps if concurrency is handled well enough in 
 D, it can catch the wave of parallel programming that is on the horizon.


I agree that D should have more support for concurrency. Putting some 
sensible support into the language is FAR better than trying to do it 
all with libraries.
Dec 13 2006
parent reply Sean Kelly <sean f4.ca> writes:
Graham St Jack wrote:

 janderson wrote:

 Given that the world of PC are heading down the path of muti-cpus:

 What features does D supply to take advantage of concurrency, over an 
 above what can be accomplished though C++ today?

 How could the language be improved to be better at concurrency 
 problems then other languages?

 (You'll not that I left out the word threading as that is only one 
 form of concurrency programming).

 -
 I'm just thinking that, perhaps if concurrency is handled well enough 
 in D, it can catch the wave of parallel programming that is on the 
 horizon.


 
 I agree that D should have more support for concurrency. Putting some 
 sensible support into the language is FAR better than trying to do it 
 all with libraries.


I think the problem is that this is a developing field, and language 
additions tend to be somewhat permanent.  Sutter's futures, for example, 
could benefit from a bit of language support (the active object part), 
but I'm not convinced the idea is quite "there" yet.  And something like 
what's in Cilk may be more mature but seems a bit too much for D. 
Better language support for concurrency will have to be a 2.0 thing, if 
only to allow more time for experimentation in library code.


Sean
Dec 14 2006
parent reply janderson <askme me.com> writes:
Sean Kelly wrote:

 Graham St Jack wrote:

 janderson wrote:

 Given that the world of PC are heading down the path of muti-cpus:

 What features does D supply to take advantage of concurrency, over an 
 above what can be accomplished though C++ today?

 How could the language be improved to be better at concurrency 
 problems then other languages?

 (You'll not that I left out the word threading as that is only one 
 form of concurrency programming).

 -
 I'm just thinking that, perhaps if concurrency is handled well enough 
 in D, it can catch the wave of parallel programming that is on the 
 horizon.


 I agree that D should have more support for concurrency. Putting some 
 sensible support into the language is FAR better than trying to do it 
 all with libraries.


 
 I think the problem is that this is a developing field, and language 
 additions tend to be somewhat permanent.  Sutter's futures, for example, 
 could benefit from a bit of language support (the active object part), 
 but I'm not convinced the idea is quite "there" yet.  And something like 
 what's in Cilk may be more mature but seems a bit too much for D. Better 
 language support for concurrency will have to be a 2.0 thing, if only to 
 allow more time for experimentation in library code.
 
 
 Sean


This may be the case, however it would be worth investigating other 
languages (in particular ones designed around concurrency).  Maybe the 
solution will be a library with D simply providing support to make the 
library easier to use then it otherwise would be.  I'm not sure. 
Something I think needs to be discussed.

What are the best and newest parallel languages out there?   What are 
the most difficult parts to solve?

What are the best libraries?  What are the hardest parts to use in those 
libraries?

I'm particularly interested if the difficult parts of lockless 
programming supported in some form.

-Joel
Dec 15 2006
parent Sean Kelly <sean f4.ca> writes:
janderson wrote:

 Sean Kelly wrote:

 Graham St Jack wrote:

 janderson wrote:

 Given that the world of PC are heading down the path of muti-cpus:

 What features does D supply to take advantage of concurrency, over 
 an above what can be accomplished though C++ today?

 How could the language be improved to be better at concurrency 
 problems then other languages?

 (You'll not that I left out the word threading as that is only one 
 form of concurrency programming).

 -
 I'm just thinking that, perhaps if concurrency is handled well 
 enough in D, it can catch the wave of parallel programming that is 
 on the horizon.


 I agree that D should have more support for concurrency. Putting some 
 sensible support into the language is FAR better than trying to do it 
 all with libraries.


 I think the problem is that this is a developing field, and language 
 additions tend to be somewhat permanent.  Sutter's futures, for 
 example, could benefit from a bit of language support (the active 
 object part), but I'm not convinced the idea is quite "there" yet.  
 And something like what's in Cilk may be more mature but seems a bit 
 too much for D. Better language support for concurrency will have to 
 be a 2.0 thing, if only to allow more time for experimentation in 
 library code.


 Sean


 
 This may be the case, however it would be worth investigating other 
 languages (in particular ones designed around concurrency).  Maybe the 
 solution will be a library with D simply providing support to make the 
 library easier to use then it otherwise would be.  I'm not sure. 
 Something I think needs to be discussed.
 
 What are the best and newest parallel languages out there?   What are 
 the most difficult parts to solve?


Very quickly (because I'm exhausted and on my way to bed), I think CSP 
is the right idea but falls apart in its "sequential" aspect.  Ideally, 
any concurrent programming approach should apply equally to traditional 
and to distributed systems in that it shouldn't matter how or where 
operations are performed so long as they're performed and the program 
state remains coherent.  ORB architectures (CORBA, DCOM) work along 
these lines as a library approach, but they put the burden of 
concurrency on the user much like mutexes and such do for traditional 
multithreaded programming.  Also, I think a process algebra would be 
ideal for any such solution to guarantee that a system built on the 
technique was provable.  And while there does appear to be some current 
work in the area, who knows how long it will take to bear fruit.

As for parallel languages... I've already mentioned Cilk and think it 
appears to be pretty decent.  Can't think of any others offhand, though 

features, because the language is actually extensible in some ways.  In 
fact, it already has a test version of Sutter's active objects and 
futures available as well as software-transactional memory, both with 
some degree of "language support."


 What are the best libraries?  What are the hardest parts to use in those 
 libraries?


ACE is probably the best for C++, though I've used it only sparingly. 
Not sure about other languages.


 I'm particularly interested if the difficult parts of lockless 
 programming supported in some form.


I'm less interested in details than in the high-level design.  If a 
library uses lock-free then great, and if it uses something else that's 
fine too, just as long as it scales appropriately, offers the 
appropriate progress guarantees, etc.  For example, CSP may be 
implemented using mutexes, lock-free, etc, but this is all invisible to 
the user.  He simply knows that tasks are being issued and completed 
concurrently, and that's all that matters.


Sean
Dec 15 2006