title: Some questionts about MPI send modes
body: <p>I'm trying to understand the specific of MPI send modes (send, bsend, ssend, rsend) and I have next questions:</p>
  
  <ol>
  <li>MPI_Send uses some buffer if the is not initialized appropriate MPI_|i|recv and message size not too big and not exceeded buffer size (otherwise, MPI_Send will wait appropriate recv). I know, it's true (this situation described here: <a href="https://stackoverflow.com/questions/20448283/deadlock-with-mpi">Deadlock with MPI</a> ).</li>
  <li>MPI_Bsend uses buffer (denoted MPI_Buffer_attach function) only when not initialized appropriate recv. <strong>It's true?</strong> </li>
  <li><strong>Buffer for MPI_Bsend is the same as that buffer for MPI_send?</strong></li>
  <li>MPI_Ssend never uses buffer. <strong>It's true?</strong> <strong>Or behavior of MPI_Ssend like MPI_Send (buffer uses, if message size is not exceeded buffer size)?</strong></li>
  </ol>
  
  <p>If an answer on my questions "it's not true", could not you give me detailed answer with explanations?</p>