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Subject: Re: [boost] [parallel_sort] Proposal
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-02-02 15:45:27

----- Original Message -----
From: "Edouard A." <edouard_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Monday, February 02, 2009 8:41 PM
Subject: Re: [boost] [parallel_sort] Proposal

>> It seems fundamentally runtime to me, since different machines or just
>> different runs will want different levels of concurrency. The
>> overhead ought to just be a few compares and arithmetic operations,
>> which would be swamped by the effort involved in the sorting.
>> I think normally I'd want to just use
>> parallel_sort(b, e, thread::hardware_concurrency())
> Maybe you're right. That's not a major design change to make it runtime, I
> can easily give it a try. We spend most of our time sorting, making an
> additional check is no big deal.
> As for TBB, I did a quick benchmark.
> As expected, TBB is faster, but not a lot.
> TBB is roughly 3 times faster than std::sort. Again, I didn't expect to get
> a x 4 gain because of the design of the Q6600 CPU.
> My implementation is 2.6 times faster than std::sort.
> Although I don't slice the data, my synchronization mechanisms are extremely
> simple, which explain why the difference isn't very big (15% advantage for
> tbb).
> I have however noticed that the behavior on sorted input is not very
> satisfactory on my side, probably for the reasons described by Phil.
> tbb::parallel_sort behavior is constant from what I can see.
> I'm going to:
> * write a parallel_merge
> * see what I can do to optimize memory allocations
> * think about the slicing issue
> * probably play left4dead instead of all the above :(


There is also Boost.ThreadPool on the queue schedule. In case this can help you?


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