title: How to send a message without a specific destination in MPI?
body: <p>I want to send a message to one of the ranks receiving a message with a specific tag. If there is any rank received the message and the message is consumed. In MPI_Recv() we can receive a message using MPI_ANY_SOURCE/MPI_ANY_TAG but the MPI_Send() can't do this. How can I send an message with unknown destination?
  The MPI_Bcast() can't do it because after receiving, I have to reply to the source process.
  Thanks.</p>