title: MPI_Isend MPI_recv lost data
body: <p>Is it possible that MPI_Recv receive message whose tag does not match?</p>
  
  <p>My logic : MPI_Isend / MPI_Recv communication. </p>
  
  <p>Node 1 Isend a message with tag 0, then Isend another message with tag 1. because there are two threads in Node 1, so the Isend action may happen at the same time.<br>
  Node 2 will probe if there is a message coming from Node 1, if yes, then receive the message. </p>
  
  <p>In my design, I want Node 2 to receive the message with tag 0 , then tag 1. But when Node 2 probe the signal that a message is coming from Node 1, it received a message whose length is the same with the tag 1 message. Then no more message from Node 1. It seems that the tag 0 message was lost. </p>
  
  <p>I am so confused, Look forward some answer. </p>