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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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