hybrid_distr_bcast.c

#include <mpi.h>
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>

#define MIN(a,b) ( (a) < (b) ? (a) : (b) )

size_t calculate_start(size_t data_count, size_t worker_count, size_t worker_id)
{
	return worker_id * (data_count / worker_count) + MIN(worker_id, data_count % worker_count);
}

size_t calculate_finish(size_t data_count, size_t worker_count, size_t worker_id)
{
	return calculate_start(data_count, worker_count, worker_id + 1);
}

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);
	
	size_t start = 0;
	size_t finish = 0;
	
	if ( argc >= 3 )
	{
		start = strtoull(argv[1], NULL, 10);
		finish = strtoull(argv[2], NULL, 10);
	}
	else
	{
		if ( my_rank == 0 )
		{
			if ( scanf("%zu %zu", &start, &finish ) != 2 )
				return (void)fprintf(stderr, "error: invalid start and finish\n"), EXIT_SUCCESS;
		}
		
		MPI_Bcast(&start, 1, MPI_UNSIGNED_LONG_LONG, /*root*/ 0, MPI_COMM_WORLD);
		MPI_Bcast(&finish, 1, MPI_UNSIGNED_LONG_LONG, /*root*/ 0, MPI_COMM_WORLD);
	}
	
	size_t my_start = start + calculate_start(finish - start, (size_t)process_count, (size_t)my_rank);
	size_t my_finish = start + calculate_finish(finish - start, (size_t)process_count, (size_t)my_rank);
	
	const size_t size = my_finish - my_start;

	printf("%s:%d: range [%zu, %zu[ size %zu\n"
		, hostname, my_rank, my_start, my_finish, size);


	#pragma omp parallel default(none) shared(my_rank, process_count, hostname, my_start, my_finish)
	{
		size_t thread_start = 0;
		size_t thread_finish = 0;
		
		#pragma omp for
		for ( size_t current = my_start; current < my_finish; ++current )
		{
			if ( thread_start == 0 )
				thread_start = current;
			thread_finish = current;
		}
		
		++thread_finish;
		
		#pragma omp critical(stdout)
		printf("\t%s:%d.%d: range [%zu,%zu[ size %zu\n"
			, hostname, my_rank, omp_get_thread_num()
			, thread_start, thread_finish, thread_finish - thread_start);
	}

	MPI_Finalize();
	return 0;
}