hybrid_distr_bcast.cpp

#include <algorithm>
#include <cstdlib>
#include <iomanip>
#include <iostream>
#include <mpi.h>
#include <omp.h>

int calculate_start(int worker_id, int workers, int finish, int begin)
{
	int range = finish - begin;
	return begin + worker_id * (range / workers) + std::min(worker_id, range % workers);
}

int calculate_finish(int worker_id, int workers, int finish, int begin)
{
	return calculate_start(worker_id + 1, workers, finish, begin);
}

int main(int argc, char* argv[])
{
	MPI_Init(&argc, &argv);
	
	int my_rank = -1;
	int process_count = -1;
	
	MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
	MPI_Comm_size(MPI_COMM_WORLD, &process_count);
	
	char hostname[MPI_MAX_PROCESSOR_NAME];
	int hostname_length = -1;
	MPI_Get_processor_name(hostname, &hostname_length);
	
	int global_start = 0;
	int global_finish = 0;
	double start_time = MPI_Wtime();
	
	if ( argc >= 3 )
	{
		global_start = atoi(argv[1]);
		global_finish = atoi(argv[2]);
	}
	else
	{
		if ( my_rank == 0 )
			std::cin >> global_start >> global_finish;

		MPI_Bcast(&global_start, 1, MPI_INT, /*root*/ 0, MPI_COMM_WORLD);
		MPI_Bcast(&global_finish, 1, MPI_INT, /*root*/ 0, MPI_COMM_WORLD);
	}
		
	const int my_start = calculate_start( my_rank, process_count, global_finish, global_start);
	const int my_finish = calculate_finish( my_rank, process_count, global_finish, global_start);
	const int my_width = my_finish - my_start;
	
	double elapsed = MPI_Wtime() - start_time;
	// hostname1:0: range [3, 12[ size 9 in 0.000123s
	std::cout << hostname << ":" << my_rank << ": range [" << my_start 
		<< ", " << my_finish << "[ size " << my_width
		<< " in " << std::fixed << std::setprecision(9) << elapsed << 's' << std::endl;

	#pragma omp parallel default(none) shared(my_rank, hostname, std::cout)
	{
		int my_thread_start = 0;
		int my_thread_finish = 0;
		
		#pragma omp for
		for ( int index = my_start; index < my_finish; ++index )
		{
			if ( my_thread_start == 0 )
				my_thread_start = index;
			my_thread_finish = index;
		}
		
		const int my_thread_width = ++my_thread_finish - my_thread_start;
		
		// hostname1:0.0: range [3,6[ size 3
		#pragma omp critical(stdout)
		std::cout << '\t' << hostname << ":" << my_rank << ":" << omp_get_thread_num() << ": range ["
			<< my_thread_start << "," << my_thread_finish << "[ size " << my_thread_width << std::endl;
	}
	
	MPI_Finalize();
}