Re: [Boost-users] thread running many times

Subject: Re: [Boost-users] thread running many times
From: Kraus Philipp (philipp.kraus_at_[hidden])
Date: 2011-09-11 16:32:17

Am 11.09.2011 um 22:14 schrieb Igor R:

>> I create a thread group and run the group with join_all(). My code shows
>> like:
>> for(i=0; i < runs; ++i) {
>>      threadgoup.join_all();
>>      do something with the results
>> }
>> So I run the thread group n times. Is this the correct way or can I call join_all only once on the group?
> 
> 
> You do not "run the group with join_all".
> join_all() waits (blocks) until the execution of all the threads in
> the group is complete - that's all.

That's correct, because the calls after the join_all need the results of all threads. The algorithm, that I use, has some parallel and serial parts, so I would run the parallel party with a thread group, wait until the group has finished and run the serial part.

> This is well documented:
> http://www.boost.org/doc/libs/1_47_0/doc/html/thread/thread_management.html#thread.thread_management.threadgroup.join_all

I have read the documentation, but there is only the postcondition explained "Every thread in the group has terminated". The algorithm is a iteration algorithm, so I have create code like this:

creating thread group
for(i=0; i < iterations; ++i) {
        run threadgroup for parallel part, till all threads finished
        run serial part
}

So I would like to ask for, if the thread group is created, and I call the join_all within the loop, each "join_all" starts the full group again on each iteration or need I create a new threadgroup on each iteration (join_all can be called only once on a group)?

Thanks

Phil