Implement the code for Connectivity.java

Add comments to explain the functionality

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

Author: vdhyasani17

examples/Connectivity.java

@@ -1,13 +1,66 @@
 /*
- * File for testing connectivity for the Java interface
+ * Test the connectivity between all processes
  * WIP
  */
 
 import mpi.*;
 
 class Connectivity {
-    static public void main(String args[]) {
-        System.out.println("Java Connectivity Test");
-    }
+    public static void main(String args[]) throws MPIException {
+        MPI.Init(args);
+
+        /*
+         * MPI_COMM_WORLD is the communicator provided when MPI is
+         * initialized. It contains all the processes that are created
+         * upon program execution.
+         */
+        int myRank = MPI.COMM_WORLD.getRank();
+        int numProcesses = MPI.COMM_WORLD.getSize();
+        Status status;
+        int verbose = 0;
+        int peerProcess;
+        String processorName = MPI.getProcessorName();
+
+        for (int i = 0; i < numProcesses; i++) {
+            if (myRank == i) { /* Find current process */
+                /* send to and receive from all higher ranked processes */
+                for (int j = i + 1; j < numProcesses; j++) {
+                    if (verbose != 0)
+                        System.out.printf("Checking connection between rank %d on %s and rank %d\n", i, processorName,
+                                j);
+
+                    int[] dataBuffer = { myRank }; /*
+                                                    * Data buffer to be sent to next process (in this case, only send
+                                                    * rank num)
+                                                    */
+                    int[] recBuffer = new int[1]; /* Data buffer that current process receives from previous process */
+
+                    /* Process must send message first then wait to receive to avoid deadlock */
+                    MPI.COMM_WORLD.send(dataBuffer, 1, MPI.INT, j, myRank);
+                    MPI.COMM_WORLD.recv(recBuffer, 1, MPI.INT, j, j);
+                }
+            } else if (myRank > i) {
+                int[] dataBuffer = { myRank };
+                int[] recBuffer = new int[1];
 
+                /* receive from and reply to rank i */
+                MPI.COMM_WORLD.recv(recBuffer, 1, MPI.INT, i, i);
+                MPI.COMM_WORLD.send(dataBuffer, 1, MPI.INT, i, myRank);
+            }
+        }
+
+        /* Wait for all processes to reach barrier before proceeding */
+        MPI.COMM_WORLD.barrier();
+
+        /*
+         * Once all ranks have reached the barrier,
+         * have only one process print out the confirmation message.
+         * In this case, we are having the "master" process print the message.
+         */
+        if (myRank == 0) {
+            System.out.printf("Connectivity test on %d processes PASSED.\n", numProcesses);
+        }
+
+        MPI.Finalize();
+    }
 }