lucky_number_who.c

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

const char* compare(double num1, double num2)
{
	if ( num1 < num2 )
		return "less than";

	if ( num1 > num2 )
		return "greater than";

	return "equals to";
}

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);

	srand( my_rank + time(NULL) );
	long my_lucky_number = rand() % 100;

	long all_min = -1;
	long all_sum = -1;
	long all_max = -1;

	MPI_Allreduce(&my_lucky_number, &all_min, /*count*/ 1, MPI_LONG, MPI_MIN, MPI_COMM_WORLD);
	MPI_Allreduce(&my_lucky_number, &all_sum, /*count*/ 1, MPI_LONG, MPI_SUM, MPI_COMM_WORLD);
	MPI_Allreduce(&my_lucky_number, &all_max, /*count*/ 1, MPI_LONG, MPI_MAX, MPI_COMM_WORLD);

	double average = (double)all_sum / process_count;

	if ( my_lucky_number == all_min )
		printf("Process %d: my lucky number (%02ld) is the minimum (%02ld)\n", my_rank, my_lucky_number, all_min);

	const char* const relation = compare(my_lucky_number, average);
	printf("Process %d: my lucky number (%02ld) is %s the average (%.2lf)\n", my_rank, my_lucky_number, relation, average);

	if ( my_lucky_number == all_max )
		printf("Process %d: my lucky number (%02ld) is the maximum (%02ld)\n", my_rank, my_lucky_number, all_max);

	MPI_Finalize();
	return 0;
}