ping_pong_ring.c (HP-UX and Linux)

#include <stdio.h>
#include <stdlib.h>
#ifndef _WIN32
#include <unistd.h>
#endif
#include <string.h>
#include <math.h>
#include <mpi.h>#define NLOOPS     		1000
#define ALIGN		      4096#define SEND(t)   		MPI_Send(buf, nbytes, MPI_CHAR, partner, (t), \
                 MPI_COMM_WORLD)
#define RECV(t)  		MPI_Recv(buf, nbytes, MPI_CHAR, partner, (t), \	                 MPI_COMM_WORLD, &status)
#ifdef CHECK
#  define SETBUF()	for (j=0; j<nbytes; j++) { \
                  		buf[j] = (char) (j + i); \
             	}#  define CLRBUF()	memset(buf, 0, nbytes)
#  define CHKBUF()	for (j = 0; j < nbytes; j++) { \
                  		if (buf[j] != (char) (j + i)) { \
                       			printf("error: buf[%d] = %d, " \
                            						"not %d\n", \
                            						j, buf[j], j + i); \
                      					break; \                  				} \			             }#else
#  define SETBUF()
#  define CLRBUF()
#  define CHKBUF()
#endifint
main(argc, argv)int              			argc;
char			            *argv[];{
     int		         i;
#ifdef CHECK
     	int		         j;#endif
     	double		           start, stop;
     	int		n        bytes = 0;
     	int		         rank, size;
     	int		         root;
     	int         		partner;
     	MPI_Status	  status;
     	char		        *buf, *obuf;
     	char		        myhost[MPI_MAX_PROCESSOR_NAME];
     	int		         len;
     	char		        str[1024];     	MPI_Init(&argc, &argv);
     	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
     	MPI_Comm_size(MPI_COMM_WORLD, &size);
     	MPI_Get_processor_name(myhost, &len);     	if (size < 2) {
     		   if ( ! rank) printf("rping: must have two+ processes\n");
        MPI_Finalize();
        		exit(0);	     }     nbytes = (argc > 1) ? atoi(argv[1]) : 0;
	     if (nbytes < 0) nbytes = 0;/*
 * Page-align buffers and displace them in the cache to avoid      collisions.
 */
     	buf = (char *) malloc(nbytes + 524288 + (ALIGN - 1));
     	obuf = buf;
     	if (buf == 0) {
           		MPI_Abort(MPI_COMM_WORLD, MPI_ERR_BUFFER);
           		exit(1);
     	}
 
     	buf = (char *) ((((unsigned long) buf) + (ALIGN - 1)) &         ~(ALIGN - 1));
     	if (rank > 0) buf += 524288;
     	memset(buf, 0, nbytes);
/*
 * Ping-pong.
 */
      	for (root=0; root<size; root++) {
            		if (rank == root) {
                			partner = (root + 1) % size;
                sprintf(str, "[%d:%s] ping-pong %d bytes ...\n",			                     root, myhost, nbytes);
/*
 * warm-up loop
 */			                 for (i = 0; i < 5; i++) {
                       SEND(1);
                       				RECV(1);
              			}/*
 * timing loop
 */
             			start = MPI_Wtime();
            			for (i = 0; i < NLOOPS; i++) {
                 				SETBUF();
                				 SEND(1000 + i);
                 				CLRBUF();
                				 RECV(2000 + i);
                				CHKBUF();
            			}
            			stop = MPI_Wtime();
 
            		sprintf(&str[strlen(str)],
                 				"%d bytes: %.2f usec/msg\n", nbytes,
                 				(stop - start) / NLOOPS / 2 * 1024 * 1024);
            			if (nbytes > 0) {
                 				sprintf(&str[strlen(str)],
                     					"%d bytes: %.2f MB/sec\n", nbytes,
                     					nbytes / (1024. * 1024.) /
                    					((stop - start) / NLOOPS / 2));
            			}
            			fflush(stdout);
      		} else if (rank == (root+1)%size) {
/*
 * warm-up loop
 */
            			partner = root;
            			for (i = 0; i < 5; i++) {
                 				RECV(1);				
                 SEND(1);
            			}
           			for (i = 0; i < NLOOPS; i++) {
                				CLRBUF();
                				RECV(1000 + i);
                				CHKBUF();
               				 SETBUF();
               				 SEND(2000 + i);
            			}
       		}
       
       		MPI_Bcast(str, 1024, MPI_CHAR, root, MPI_COMM_WORLD);
       		if (rank == 0) {
              			printf("%s", str);
       		}
    	}
 
    	free(obuf);
    	MPI_Finalize();
    	exit(0);}