% mpicc -o pingpong -O pingpong.c % mpirun -np 2 pingpong Kind n time (sec) Rate (MB/sec) Send/Recv 1 0.000095 0.084078 Send/Recv 2 0.000095 0.168901 Send/Recv 4 0.000097 0.330131 Send/Recv 8 0.000132 0.484799 Send/Recv 16 0.000133 0.962880 Send/Recv 32 0.000145 1.770964 Send/Recv 64 0.000162 3.166782 Send/Recv 128 0.000195 5.245853 Send/Recv 256 0.000259 7.900853 Send/Recv 512 0.000352 11.623159 Send/Recv 1024 0.000566 14.484053 Send/Recv 2048 0.001055 15.530778 Send/Recv 4096 0.001642 19.952966 Send/Recv 8192 0.002680 24.456014 Send/Recv 16384 0.004773 27.462645 Send/Recv 32768 0.008801 29.786806 Send/Recv 65536 0.016895 31.032414 Send/Recv 131072 0.032911 31.860559 Send/Recv 262144 0.065010 32.258846 Send/Recv 524288 0.129104 32.487790 Send/Recv 1048576 0.258655 32.431620