Add collective comp code

hpc/hello-world/mpi_bcred.c

+#include "mpi.h"
+#include <stdio.h>
+#include <math.h>
+#define DATASIZE 10
+
+int main(int argc, char **argv) {
+    int myid, numprocs;
+    int i, x, low, high, myresult=0, result;
+
+    int data[DATASIZE] = {1,2,3,4,5,6,7,8,9,10}
+
+    MPI_Init(&argc, &argv);
+    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
+    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
+
+    MPI_Bcast(data, DATASIZE, MPI_INT, 0, MPI_COMM_WORLD);
+
+    /* add portion of data */
+    x = DATASIZE/numprocs;	/* must be an integer */
+    low = myid * x;
+    high = low + x;
+    for(i=low; i<high; i++) {
+        myresult += data[i];
+    }
+    printf("%d has %d\n", myresult, myid);
+
+    MPI_Reduce(&myresult, &result, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
+
+    if(0 == myid) {
+        printf("The sum is %d.\n", result);
+    }
+
+    MPI_Finalize();
+}

hpc/hello-world/mpi_scatter.c

+#include "mpi.h"
+#include <stdio.h>
+#define SIZE 4
+
+int main(int argc, char** argv)  {
+    int numtasks, rank, sendcount, recvcount, source;
+    float sendbuf[SIZE][SIZE] = {
+        {1.0, 2.0, 3.0, 4.0},
+        {5.0, 6.0, 7.0, 8.0},
+        {9.0, 10.0, 11.0, 12.0},
+        {13.0, 14.0, 15.0, 16.0}
+    };
+    float recvbuf[SIZE];
+
+    MPI_Init(&argc,&argv);
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
+
+    if (numtasks == SIZE) {
+        source = 1;
+        sendcount = SIZE;
+        recvcount = SIZE;
+        MPI_Scatter(sendbuf,sendcount,MPI_FLOAT,recvbuf,recvcount,
+                    MPI_FLOAT,source,MPI_COMM_WORLD);
+
+        printf("rank= %d  Results: %f %f %f %f\n",rank,recvbuf[0],
+               recvbuf[1],recvbuf[2],recvbuf[3]);
+    }
+    else
+        printf("Must specify %d processors. Terminating.\n",SIZE);
+
+    MPI_Finalize();
+}

hpc/hello-world/mpi_send.c

-#include <mpi.h>
+#include "mpi.h"
 #include <stdio.h>
 
 int main(int argc, char** argv) {