[mvapich-discuss] Bad performance of MVAPICH 1.8.1

[Stephan Wolf]

Hi,

I had to switch to MVAPICH 1.9b in order to use the MPE environement
for benchmarking. However I have expierenced significant reduction of
the performance when using MVAPICH 1.9. It seems to be caused probably
some bug in the RPUT protocol, because the R3 protocol works fine. I
guess that the registration cache is not used.

To illustrate my findings. Here is the pseudocode of my program:
--------
\\ Take time
for(i to 20){
  for(a to n) IRecv(rec_buffer[a])
  for(a to n) ISend(send_buffer[a])
  waitForAllRecv()
  waitForAllSend()
}
\\ Plot time
-------
A diagram showing the effect can be found at:
http://postimg.org/image/gddde14fr/

What is the reason for that? Can I just stick to the R3 rendez-vous
protocol, or does it has some disadvantage (like higher memory
bandwidth consumption)

Thanks

Stephan