% mpicc -o pingpong -O pingpong.c % mpirun -np 4 pingpong Kind n time (sec) Rate (MB/sec) Send/Recv 1 0.001731 0.004623 Send/Recv 2 0.001696 0.009432 Send/Recv 4 0.002104 0.015211 Send/Recv 8 0.002233 0.028660 Send/Recv 16 0.001733 0.073871 Send/Recv 32 0.001886 0.135732 Send/Recv 64 0.002374 0.215682 Send/Recv 128 0.003464 0.295582 Send/Recv 256 0.004840 0.423155 Send/Recv 512 0.009620 0.425757 Send/Recv 1024 0.017626 0.464781 Send/Recv 2048 0.028715 0.570573 Send/Recv 4096 0.057779 0.567122 Send/Recv 8192 0.130371 0.502687 Send/Recv 16384 0.206248 0.635507 Send/Recv 32768 0.452411 0.579437 Send/Recv 65536 1.154206 0.454241 Send/Recv 131072 2.241706 0.467758 Send/Recv 262144 4.576753 0.458218 Send/Recv 524288 8.277655 0.506702 Send/Recv 1048576 15.917955 0.526990