Added test program to familiarize with MPI.

modsim/ass4_taddeus/ring.c

@@ -2,14 +2,17 @@
 #include <stdio.h>
 #include <mpi.h>
 
-double *data = {.0};
+double data[1] = {.0};
 
-void initialize_ring(void) {
+void initialize_ring(int tasks) {
     double received;
+    MPI_Status status;
 
-    puts("Sending first data");
-    MPI_Send(data, 1, MPI_DOUBLE, 2, MPI_ANY_TAG, MPI_COMM_WORLD);
-    MPI_Recv(&received, 1, MPI_DOUBLE, tasks - 1, MPI_ANY_TAG, MPI_COMM_WORLD);
+    printf("Sending first data...");
+    MPI_Send(data, 1, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD);
+    puts("sent");
+    MPI_Recv(&received, 1, MPI_DOUBLE, tasks - 1, MPI_ANY_TAG, MPI_COMM_WORLD,
+            &status);
 
     if( received != *data )
         printf("Received data does not match (sent: %f, received: %f)\n",
@@ -20,10 +23,15 @@ void initialize_ring(void) {
 
 void pass_data(int tasks, int rank) {
     double received;
-
-    printf("Task %d sending data\n", task);
-    MPI_Recv(&received, 1, MPI_DOUBLE, (rank - 1 + tasks) % tasks, MPI_ANY_TAG, MPI_COMM_WORLD);
-    MPI_Send(data, 1, MPI_DOUBLE, (rank + 1) % tasks, MPI_ANY_TAG, MPI_COMM_WORLD);
+    MPI_Status status;
+    int target = (rank + 1) % tasks, source = (rank - 1 + tasks) % tasks;
+
+    MPI_Recv(&received, 1, MPI_DOUBLE, source, MPI_ANY_TAG, MPI_COMM_WORLD,
+            &status);
+    printf("Task %d received data from %d, sending to %d...", rank, source,
+            target);
+    MPI_Send(data, 1, MPI_DOUBLE, target, 0, MPI_COMM_WORLD);
+    puts("sent");
 }
 
 int main(int argc, char **argv) {
@@ -38,7 +46,7 @@ int main(int argc, char **argv) {
     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
 
     if( !rank )
-        initialize_ring();
+        initialize_ring(tasks);
     else
         pass_data(tasks, rank);
 

modsim/ass4_taddeus/ring_test.c

+#include <stdlib.h>
+#include <stdio.h>
+#include <mpi.h>
+
+double data[1] = {.0};
+
+void initialize_ring(int tasks) {
+    double received;
+    MPI_Status status;
+
+    printf("Sending first data...");
+    MPI_Send(data, 1, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD);
+    puts("sent");
+    MPI_Recv(&received, 1, MPI_DOUBLE, tasks - 1, MPI_ANY_TAG, MPI_COMM_WORLD,
+            &status);
+
+    if( received != *data )
+        printf("Received data does not match (sent: %f, received: %f)\n",
+                *data, received);
+    else
+        puts("Data received succesfully");
+}
+
+void pass_data(int tasks, int rank) {
+    double received;
+    MPI_Status status;
+    int target = (rank + 1) % tasks, source = (rank - 1 + tasks) % tasks;
+
+    MPI_Recv(&received, 1, MPI_DOUBLE, source, MPI_ANY_TAG, MPI_COMM_WORLD,
+            &status);
+    printf("Task %d received data from %d, sending to %d...", rank, source,
+            target);
+    MPI_Send(data, 1, MPI_DOUBLE, target, 0, MPI_COMM_WORLD);
+    puts("sent");
+}
+
+int main(int argc, char **argv) {
+    int tasks, rank, error;
+
+    if( (error = MPI_Init(&argc, &argv)) != MPI_SUCCESS ) {
+        printf("MPI_init failed (error %d)\n", error);
+        MPI_Abort(MPI_COMM_WORLD, error);
+    }
+
+    MPI_Comm_size(MPI_COMM_WORLD, &tasks);
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+    if( !rank )
+        initialize_ring(tasks);
+    else
+        pass_data(tasks, rank);
+
+    MPI_Finalize();
+}