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POMPI Send and receive questions
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copied!<p>I have questions about MPI send and receive operations. </p> <p>Suppose, we have 2 MPI threads that try to send message to each other. Following are three code snippets doing that:</p> <p>First (Blocking 'send' and 'receive'):</p> <pre><code>... int data = ...; ... MPI_Send( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD ); MPI_Status status; MPI_Recv( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD, &status ); ... </code></pre> <p>Second (Non-blocking 'send' but blocking 'receive'):</p> <pre><code>... int data = ...; ... MPI_Request request; MPI_Isend( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD, &request); MPI_Status status; MPI_Recv( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD, &status ); // Synchronize sender & receiver MPI_Wait( &request, &status); ... </code></pre> <p>Third (Non-blocking 'receive' with blocking 'send'):</p> <pre><code>... int data = ...; ... MPI_Request request; MPI_Irecv( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD, &request ); MPI_Send( &data, sizeof( int ), MPI_INT, (my_id == 0)?1:0, 0, MPI_COMM_WORLD); MPI_Status status; // Synchronize sender & receiver MPI_Wait( &request, &status); ... </code></pre> <p>I guess there are potential problems with above three code but I want your opinion. So, I have the following questions:</p> <ol> <li><p>What are the (potential) problems (if any) with 3 codes given above?</p></li> <li><p>Which of the above three code are valid/correct considering MPI standard so that it can work with all MPI implementations? </p></li> <li><p>What is the best way (if not one of above 3 please write it) to do that?</p></li> <li><p>In the third code, what if we change the order of MPI_Irecv and MPI_Send call?</p></li> </ol> <p>PS: By the way, I have tried executing them using Scali MPI and all of them worked!</p>

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