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- //---------------------------------------------------------------------------//
- // Copyright (c) 2014 Kyle Lutz <kyle.r.lutz@gmail.com>
- //
- // Distributed under the Boost Software License, Version 1.0
- // See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt
- //
- // See http://boostorg.github.com/compute for more information.
- //---------------------------------------------------------------------------//
- #include <algorithm>
- #include <iostream>
- #include <vector>
- #include <tbb/parallel_for.h>
- #include "perf.hpp"
- // example from: http://www.threadingbuildingblocks.org/docs/help/reference/algorithms/parallel_for_func.htm
- using namespace tbb;
- template<typename Iterator>
- struct ParallelMergeRange {
- static size_t grainsize;
- Iterator begin1, end1; // [begin1,end1) is 1st sequence to be merged
- Iterator begin2, end2; // [begin2,end2) is 2nd sequence to be merged
- Iterator out; // where to put merged sequence
- bool empty() const {return (end1-begin1)+(end2-begin2)==0;}
- bool is_divisible() const {
- return (std::min)( end1-begin1, end2-begin2 ) > grainsize;
- }
- ParallelMergeRange( ParallelMergeRange& r, split ) {
- if( r.end1-r.begin1 < r.end2-r.begin2 ) {
- std::swap(r.begin1,r.begin2);
- std::swap(r.end1,r.end2);
- }
- Iterator m1 = r.begin1 + (r.end1-r.begin1)/2;
- Iterator m2 = std::lower_bound( r.begin2, r.end2, *m1 );
- begin1 = m1;
- begin2 = m2;
- end1 = r.end1;
- end2 = r.end2;
- out = r.out + (m1-r.begin1) + (m2-r.begin2);
- r.end1 = m1;
- r.end2 = m2;
- }
- ParallelMergeRange( Iterator begin1_, Iterator end1_,
- Iterator begin2_, Iterator end2_,
- Iterator out_ ) :
- begin1(begin1_), end1(end1_),
- begin2(begin2_), end2(end2_), out(out_)
- {}
- };
- template<typename Iterator>
- size_t ParallelMergeRange<Iterator>::grainsize = 1000;
- template<typename Iterator>
- struct ParallelMergeBody {
- void operator()( ParallelMergeRange<Iterator>& r ) const {
- std::merge( r.begin1, r.end1, r.begin2, r.end2, r.out );
- }
- };
- template<typename Iterator>
- void ParallelMerge( Iterator begin1, Iterator end1, Iterator begin2, Iterator end2, Iterator out ) {
- parallel_for(
- ParallelMergeRange<Iterator>(begin1,end1,begin2,end2,out),
- ParallelMergeBody<Iterator>(),
- simple_partitioner()
- );
- }
- int main(int argc, char *argv[])
- {
- perf_parse_args(argc, argv);
- std::cout << "size: " << PERF_N << std::endl;
- std::vector<int> v1 = generate_random_vector<int>(PERF_N / 2);
- std::vector<int> v2 = generate_random_vector<int>(PERF_N / 2);
- std::vector<int> v3(PERF_N);
- std::sort(v1.begin(), v1.end());
- std::sort(v2.begin(), v2.end());
- perf_timer t;
- for(size_t trial = 0; trial < PERF_TRIALS; trial++){
- t.start();
- ParallelMerge(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin());
- t.stop();
- }
- std::cout << "time: " << t.min_time() / 1e6 << " ms" << std::endl;
- return 0;
- }
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