----- Original Message ----- From: "Edouard A." <edouard@fausse.info> To: <boost@lists.boost.org> Sent: Sunday, March 08, 2009 7:48 PM Subject: Re: [boost] [threadpool] version 22 with default pool
I have implemented a parallel_sort that is a bit slower than tbb with threadpool (see below for the code).
Benchmark results:
std::fill 0..1000000 ok : 1 elapsed: 0.01 tbb::parallel_for fill 0..1000000 ok : 1 elapsed: 0.01 std::sort reverse 0..1000000 ok : 1 elapsed: 0.11 tbb::parallel_sort reverse 0..1000000 ok : 1 elapsed: 0.037 boost::tp::sort reverse 0..1000000 ok : 1 elapsed: 0.048
Machine: Q6600 - 4 GiB Ram - Running Vista 64 - x64 release build with full optimizations.
Some remarks:
* shutdown() renders the thread pool unusable (marks it terminated). This is not what I was looking for. Ideally, a wait() method that just waits for the pool to have no tasks left to process would be better. I would find it cumbersome to manually wait for the result of each task. My 2c. * It's difficult to properly benchmark the two on my development machine that is probably using one core to do things background work * Instrumentation seems to show that the _entry method of the pool is extremely slow. I have not investigated further. * boost::tp::sort benchmark includes thread destruction... Probably eats up some micro secs * My code is probably sub-optimal
The code:
template <typename RandomIterator> RandomIterator pivot_partition(RandomIterator first, RandomIterator last) { typedef RandomIterator iterator_type; typedef typename iterator_type::difference_type difference_type; typedef typename iterator_type::value_type value_type;
iterator_type pivot = first + std::distance(first, last) / 2;
// we partition value_type pivot_value = *pivot;
// we "save" the pivot in putting it to the first place std::iter_swap(first, pivot);
// we skip the pivot otherwise the partitioning won't work as expected iterator_type par_start = first + 1;
std::less<value_type> pred;
pivot = std::partition(par_start, last, std::bind2nd(pred, pivot_value));
// we restore the pivot std::iter_swap(--pivot, first);
return pivot; }
template <typename RandomIterator, typename Pool> void rec_pivot_partition(RandomIterator first, RandomIterator last, Pool & p) { if (std::distance(first, last) > 1000) { RandomIterator pivot = pivot_partition(first, last); rec_pivot_partition(first, pivot, p); rec_pivot_partition(pivot, last, p); } else { p.submit(boost::bind(&std::sort<iterator_type>, first, last)); }
};
Hi, I don't see when the merge is done. Have you tested that the result is ordered? Could you attach the complete file? Thanks, Vicente