added docker project

documents/Programmierparadigmen/scripts/mpi/mpi-sum-reduce.c

@@ -0,0 +1,35 @@
+// Quelle: Klausur vom SS 2013 am KIT bei 
+// Prof. Dr.-Ing. Gregor Snelting
+void my_int_sum_reduce(int *sendbuf, 
+    int *recvbuf, int count,
+    int root, MPI_Comm comm)
+{
+    int size, rank;
+    MPI_Comm_size(comm, &size);
+    MPI_Comm_rank(comm, &rank);
+    if (rank == root) {
+        /* Initialize recvbuf with our own values. */
+        for (int i = 0; i < count; ++i) {
+            recvbuf[i] = sendbuf[i];
+        }
+
+        /* Receive values from every other node
+           and accumulate. */
+        for (int i = 0; i < size; ++i) {
+            if (i == root)
+                continue;
+
+            int other[count];
+            MPI_Recv(other, count, MPI_INT, 
+                i, 0, comm, MPI_STATUS_IGNORE);
+            
+            for (int j = 0; j < count; ++j) {
+                recvbuf[j] += other[j];
+            }
+        }
+    } else {
+        /* Send our values to root. */
+        MPI_Send(sendbuf, count, MPI_INT, 
+            root, 0, comm);
+    }
+}