Change nonblocking iSend/iRecv to sendRecv operation

Signed-off-by: vdhyasani17 <[email protected]>

Author: vdhyasani17

examples/Connectivity.java

@@ -38,34 +38,28 @@ public static void main(String args[]) throws MPIException {
                                 j);
 
                     /*
-                     * rank is the Buffer passed into iSend to send to rank j.
+                     * rank is the Buffer passed into sendRecv to send to rank j.
                      * rank is populated with myRank, which is the data to send off
-                     * peer is the Buffer received from rank j from iRecv
+                     * peer is the Buffer received from rank j to current rank
                      */
                     IntBuffer rank = MPI.newIntBuffer(1);
                     IntBuffer peer = MPI.newIntBuffer(1);
                     rank.put(0, myRank);
 
                     /*
-                     * To avoid deadlocks, use non-blocking communication iSend and iRecv
-                     * This will allow the program to progress, in the event that
-                     * two ranks both send to each other at the same time and could
-                     * potentially cause deadlock. The ranks can send their requests
-                     * without halting the program and immediately
+                     * To avoid deadlocks, use combined sendRecv operation.
+                     * This performs a send and recv as a combined atomic operation
+                     * and allow MPI to efficiently handle the requests internally.
                      */
-                    Request sendReq = MPI.COMM_WORLD.iSend(rank, 1, MPI.INT, j, myRank);
-                    Request recvReq = MPI.COMM_WORLD.iRecv(peer, 1, MPI.INT, j, j);
-                    sendReq.waitFor();
-                    recvReq.waitFor();
+                    MPI.COMM_WORLD.sendRecv(rank, 1, MPI.INT, j, myRank, peer, 1, MPI.INT, j, j);
                 }
             } else if (myRank > i) {
                 IntBuffer rank = MPI.newIntBuffer(1);
                 IntBuffer peer = MPI.newIntBuffer(1);
                 rank.put(0, myRank);
 
                 /* receive from and reply to rank i */
-                MPI.COMM_WORLD.iRecv(peer, 1, MPI.INT, i, i).waitFor();
-                MPI.COMM_WORLD.iSend(rank, 1, MPI.INT, i, myRank).waitFor();
+                MPI.COMM_WORLD.sendRecv(rank, 1, MPI.INT, i, myRank, peer, 1, MPI.INT, i, i);
             }
         }