% mpicc -o pingpong pingpong.c % mpirun -np 2 pingpong Kind (np=2) n time (sec) Rate (MB/sec) Send/Recv 1 0.003632 0.002203 Send/Recv 2 0.003630 0.004408 Send/Recv 4 0.003609 0.008868 Send/Recv 8 0.003647 0.017551 Send/Recv 16 0.003686 0.034728 Send/Recv 32 0.003715 0.068915 Send/Recv 64 0.003782 0.135391 Send/Recv 128 0.004294 0.238496 Send/Recv 256 0.005254 0.389761 Send/Recv 512 0.007625 0.537145 Send/Recv 1024 0.011954 0.685265 Send/Recv 2048 0.021332 0.768066 Send/Recv 4096 0.038777 0.845026 Send/Recv 8192 0.076762 0.853750 Send/Recv 16384 0.146377 0.895441 Send/Recv 32768 0.298841 0.877202 Send/Recv 65536 0.579786 0.904278 Send/Recv 131072 1.193957 0.878236 Send/Recv 262144 2.325686 0.901735 Send/Recv 524288 4.693125 0.893712 Send/Recv 1048576 9.318751 0.900186