Re: [boost] [thread] countdown_latch

Subject: Re: [boost] [thread] countdown_latch
From: Gaetano Mendola (mendola_at_[hidden])
Date: 2013-05-25 08:45:43

On 21/05/2013 07.13, Vicente J. Botet Escriba wrote:
> Le 20/05/13 22:09, Gaetano Mendola a écrit :
>> On 27/04/2013 09.05, Vicente J. Botet Escriba wrote:
>>> Le 22/04/13 10:16, Michael Marcin a écrit :
>>>> On 4/21/2013 11:30 PM, Vicente J. Botet Escriba wrote:
>>>>
>>> Hi,
>>>> Back on topic of latches and barriers.
>>>> I was reading up on Java's CyclicBarrier and found its await return
>>>> value pretty interesting and probably fairly free to implement.
>>>>
>>>> "...each invocation of await() returns the arrival index of that
>>>> thread at the barrier."
>>>>
>>>> "the arrival index of the current thread, where index getParties() - 1
>>>> indicates the first to arrive and zero indicates the last to arrive."
>>>>
>>>> To do this in boost::thread::barrier you would just have to cache
>>>> m_count right after the decrement and return it instead of the current
>>>> true/false.
>>>>
>>>>
>>>
>>> Yes, boost::barrier return true for the last wait. The change would be
>>> quite simple, but what would be he utility of such an index?
>>>
>>> I have implemented a first prototype of a latch class that could be used
>>> also as a barrier. I don't know if the name is the good one then.
>>> I have also implemented a completion_latch class that is able to call a
>>> function when the counter reaches zero. I'm not satisfied with the
>>> current implementation as it needs a lot of synchronization.
>>>
>>> The change set is https://svn.boost.org/trac/boost/changeset/84055. To
>>> see the sources, you would need to update the trunk or to take a look at
>>> https://svn.boost.org/svn/boost/trunk/boost/thread/
>>>
>>> Please let me know what do you think.
>>
>> What's the plan for this countdown_latch is it candidate to be included
>> in version 1.54 ?
>>
>>
> No, documentation and tests are missing. I hope it will be ready for
> 1.55. This and other addition will be experimental and its interface
> will be subject to some changes.
> E.g. I have not decided yet how to provide cyclic latches.

Given the fact I have my own implementation of a latch, can you please
explain what a cyclic latch is, to see if my latch already provide
the feature. I will propose my implementation of latch.

Regards
Gaetano Mendola