Hi, ----- Original Message ----- From: "Edouard A." <edouard@fausse.info> To: <boost@lists.boost.org> Sent: Monday, February 02, 2009 7:21 PM Subject: Re: [boost] [parallel_sort] Proposal
On Mon, 02 Feb 2009 17:41:58 +0000, "Phil Endecott" <spam_from_boost_dev@chezphil.org> wrote:
So basically it's something like this:
thread t( sort(begin,mid) ); sort(mid,end); t.join(); merge(begin,mid,end); // [*]
Exactly, with some differences as I do a memory copy before the thread and I run two threads.
Working on different buffers allows to prevent hidden system locks when you reach the middle.
Please could you be more precise, which kind of hidden system locks?
so it's more like
buffer = new []; copy(...) thread t1(sort(buffer,...);
buffer2 = new []; copy(...) thread t2(sort(buffer2, ...);
t2.join(); t1.join();
merge(buffer, buffer2, result);
The second thread is not realy useful, as noted by Phil. I would like to be able to write something more generic, something like: template < typename DirectSolver, typename Composer, typename AsynchronousExecutor, typename Input> void inplace_solve(AsynchronousExecutor& ae, Problem& input) { // if (problem is small) if (size(range) < concurrency_threshold) { // directly solve problem DirectSolver()(input); } else { // split problem into independent parts BOOST_AUTO(partition, partition_view(input)); // evaluates asynchronously inplace_solve on each element of the partition // using the asynchronous executor as scheduler wait_for_all(ae, inplace_solve, partition); // compose the result in place from subresults Composer()(partition); } } So parallel sort could be template <typename Range> void parallel_sort(range& range) { boost::tp::pool<> ae; parallel::inplace_solve<sort, merge>(ae, input); } I'm working on a Asynchronous Execution framework that you can get from http://www.boostpro.com/vault/index.php?action=downloadfile&filename=interthreads.zip&directory=Concurrent%20Programming&. It provides a wait_for_all function which will fork each function except the last one which will be executed in the current thread. So if you make 4 partitions you need to use it as wait_for_all(ae, bind(inplace_solve, at_c<0>(partition)), bind(inplace_solve, at_c<1>(partition)), bind(inplace_solve, at_c<2>(partition)), bind(inplace_solve, at_c<3>(partition)), ); I'll try to implement this overloading. template< typename AE, typename F, typename Sequence> typename result_of::wait_for_all<AE, F,Sequence >::type wait_for_all( AE& ae, F f, Sequence seq ); HTH, Vicente