MPI on a single machine dualcore?

This depends on your MPI implementation, of course. Most likely, it will create three processes, and use shared memory to exchange the messages. This will work just fine: the operating system will dispatch the two CPUs across the three processes, and always execute one of the ready processes.

If a process waits to receive a message, it will block, and the operating system will schedule one of the other two processes to run - one of which will be the one that is sending the message.

Martin has given the right answer and I've plus-1ed him, but I just want to add a few subtleties which are a little too long to fit into the comment box.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.