% 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