[mpich-discuss] mpich-discuss Digest, Vol 14, Issue 37

[BryantMichael Bryant]

hello,recently i had do a research about mpich2 to compare the "nemesis" and "shm" channel.in the research,first, i make install mpich2 with nemesis,and then make install with shm. my purpose is to compare the latency and bandwidth by using the two channel in a single SMP node.

the test enviroment is Intel(R) Xeon(R) CPU X5355 2.66GH,cache size : 4096 KB

and  the test result shows that the bandwidth,when the mpi message size from 1-32Byte,the bandwidth shows similar;then the message size from 32-512B,the nemesis shows little better than shm;but after 512B to 1MB(my test use OSU benchmark,message size from 1Byte-4MB),the shm show more better than the nemesis,the peak is about 1800MBps(shm),but the nemesis is only 1100MBps;from 1MB to 4MB,the bandwidth in shm decrease rapidly,anyway it also better than the nemesis,when the message size come to 4MB,the nemesis and shm show the similar bandwidth.

my question is: why the shm show the more better performance than the nemesis? is it owing to the data transfer method or shm has some optimize functions ?

pls tell me ,thank you!
 		 	   		  
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