Separate HTML for Basic Foil 21 Implementation of MPSHIFT(+1, SOURCE,DEST)

Basic HTML version of Foils prepared 2 October 1995

Foil 21 Implementation of MPSHIFT(+1, SOURCE,DEST)

From New CPS615 Foils-- D 23 September 95 CPS615 Basic Simulation Track for Computational Science -- Fall Semester 95. by Geoffrey C. Fox

Consider for example, shift to right

Then Processors 0 .. Nproc-2 Send to right

Processors 1 .. Nproc-1 Receive from left

We can't necessarily send all messages and then receive all messages. "Standard" send can be "blocking" i.e. will not return unless receive completed by destination processor. In this case, we can deadlock as all "hang" after send, waiting for receive

So we are more careful