mpi_pqsort.c

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


int validate (int *output, int num_elements)
{
	int i = 0;
	assert (output != NULL);
	for (i = 0; i < num_elements - 1; i++)
	  {
		  if (output[i] > output[i + 1])
		    {
			    printf ("************* NOT sorted *************\n");
                            printf("Element [%d]  = %d is greater than [%d] = %d \n", i, output[i], i+1, output[i+1]);
			    return -1;
		    }
	  }
	printf ("============= SORTED ===========\n");
        return 0;
}

int main (int argc, char **argv)
{
	int *input = NULL;
	//int *output = NULL;
	int num_elements;
        int  i = 0;
        int numtasks, rank, rc;
        unsigned int timeval = 0;
        MPI_Status recv_status;

        int elems_per_task;
        int adjust;
        int part_start;

        rc = MPI_Init(&argc, &argv);
        if(rc != MPI_SUCCESS) {
                printf("Error starting MPI program. Terminating. \n");
                MPI_Abort(MPI_COMM_WORLD, rc);
        }

        MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
        MPI_Comm_rank(MPI_COMM_WORLD, &rank);


        printf("Running with rank : %d\n", rank);

	if (argc < 2){
		  printf ("Usage: ./pqsort <num of elements>\n");
	}
        if( argc == 3){
                timeval = (unsigned int)atof(argv[3]);
        }

        num_elements = atoi (argv[1]);

        printf("Running with rank [%d] and num_elements[%d]\n", rank, num_elements);

        if (!(input = (int *) calloc (num_elements, sizeof (int)))){
                  printf ("Memory error\n");
                  exit (EXIT_FAILURE);
        }

        if(rank == 0){
                if(timeval == 0){
                        timeval = time ( NULL );
                }
                printf("The seed is : %d\n", timeval);
                srand(timeval);
                for(i = 0; i < num_elements ;i++){
                        input[i] = i;
                        //input[i] = rand()%1000000;
                }
                elems_per_task = (num_elements/numtasks);
                adjust  = num_elements - elems_per_task*numtasks;
                if(adjust > 0){
                        part_start = elems_per_task + 1;
                        adjust --;
                }
                else{
                        part_start = elems_per_task;
                }
                for(i = 1; i < numtasks; i++){
                        if(adjust > 0){
                                MPI_Send((input + part_start), elems_per_task + 1, MPI_INT, i, 0, MPI_COMM_WORLD);
                                part_start += (elems_per_task + 1);
                                adjust -- ;
                        }
                        else{
                                MPI_Send((input + part_start), elems_per_task, MPI_INT, i, 0, MPI_COMM_WORLD);
                                part_start += (elems_per_task);
                        }
                }

        }
        else{
                printf("My rank is : %d\n", rank);
                elems_per_task = (num_elements/numtasks);
                adjust  = num_elements - elems_per_task*numtasks;
                part_start = 0;
                for(i=0; i < rank; i++){
                        if(adjust > 0){
                                part_start += (elems_per_task + 1);
                                adjust --;
                        }
                        else{
                                part_start += (elems_per_task);
                        }
                }
                        
                if(adjust > 0){
                        MPI_Recv((input + part_start), elems_per_task+ 1, MPI_INT, 0, 0, MPI_COMM_WORLD, &recv_status);
                }
                else{
                        MPI_Recv((input + part_start), elems_per_task, MPI_INT, 0, 0, MPI_COMM_WORLD, &recv_status);
                }
                for(i = part_start; i < part_start + elems_per_task; i ++){
                        printf("[%d] [%d] = [%d] \n", rank, i, input[i]);
                }

        }


        

        MPI_Finalize();

        /*


	if(validate (output, num_elements) != 0)
                return EXIT_FAILURE;
                */
	return EXIT_SUCCESS;
}