MPI Non-blocking and Collective Communication Demos

Change log:
* slurm script for non-blocking demos
* add MPI_Gather demo
* add MPI_Reduce demo
* add MPI_Request_free's to heat equation persistent commlunication
  solution
* use 40 cores for collective demos

D4-MPI/02-MPI-Non-blocking/demo/batch.slurm

+#!/bin/bash
+#SBATCH --partition=CourseDevQ
+#SBATCH --reservation=SOHPCCourse
+#SBATCH --nodes=1
+#SBATCH --time=00:10:00
+#SBATCH --account=course
+
+
+module load gcc openmpi/gcc/4.0.5
+mpicc $1 -o prog
+
+cd $SLURM_SUBMIT_DIR
+
+
+# Run MPI code
+mpirun -n 2 ./prog 
+
+module purge
+rm ./prog

D4-MPI/02-MPI-Non-blocking/solution/heat_equation/persistent_main.c

@@ -52,6 +52,12 @@ void iterate(double *u, double *u_prev, const int nx, const int ny,
         req_prev = req;
         req = temp_req;
     }
+
+    /* free the MPI_Request objects */ 
+    for (int i = 0; i < 4; i++) {
+        MPI_Request_free(&req[i]);
+        MPI_Request_free(&req_prev[i]);
+    }
 }
 
 int main(int argc, char *argv[]) {

D4-MPI/03-MPI-Collective-Comms/demo/batch.slurm

+#!/bin/bash
+#SBATCH --partition=CourseDevQ
+#SBATCH --reservation=SOHPCCourse
+#SBATCH --nodes=1
+#SBATCH --time=00:10:00
+#SBATCH --account=course
+
+
+module load gcc openmpi/gcc/4.0.5
+mpicc $1 -o prog
+
+cd $SLURM_SUBMIT_DIR
+
+
+# Run MPI code
+mpirun -n 40 ./prog 
+
+module purge
+rm ./prog

D4-MPI/03-MPI-Collective-Comms/demo/collective_gather.c

+#include <stdio.h>
+#include <mpi.h>
+
+int main(int argc, char *argv[]) {
+    MPI_Init(&argc, &argv);
+
+    int rank, size;
+
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    int ranks[size];
+
+    double before_time = MPI_Wtime();
+    /* gather ranks at root */
+    MPI_Gather(&rank, 1, MPI_INT, ranks, 1, MPI_INT, 0, MPI_COMM_WORLD);
+
+    /* print ranks */
+    if (rank == 0) {
+        printf("Transfer took %lfs\n", MPI_Wtime() - before_time);
+        printf("The MPI_COMM_WORLD ranks are:\n");
+        for (int i = 0; i < size; i++) {
+            printf("%d ", ranks[i]);
+        }
+        printf("\n");
+    }
+
+    MPI_Finalize();
+    return 0;
+}

D4-MPI/03-MPI-Collective-Comms/demo/collective_reduce.c

+#include <stdio.h>
+#include <mpi.h>
+
+int main(int argc, char *argv[]) {
+    MPI_Init(&argc, &argv);
+
+    int rank, size;
+
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    int rank_sum = 0;
+
+    double before_time = MPI_Wtime();
+    /* collect ranks at root and add to running sum */
+    MPI_Reduce(&rank, &rank_sum, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
+
+    /* print ranks */
+    if (rank == 0) {
+        printf("Sum took %lfs\n", MPI_Wtime() - before_time);
+        printf("The sum of MPI_COMM_WORLD ranks is %d\n", rank_sum);
+    }
+
+    MPI_Finalize();
+    return 0;
+}

D4-MPI/03-MPI-Collective-Comms/demo/gather.c

+#include <stdio.h>
+#include <mpi.h>
+
+int main(int argc, char *argv[]) {
+    MPI_Init(&argc, &argv);
+
+    int rank, size;
+
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    int ranks[size];
+
+    double before_time = MPI_Wtime();
+    /* gather ranks at root */
+    if (rank > 0) {
+        MPI_Send(&rank, 1, MPI_INT, 0, rank, MPI_COMM_WORLD);
+    } else {
+        ranks[0] = rank;
+        for (int i = 1; i < size; i++) {
+            MPI_Recv(&ranks[i], 1, MPI_INT, i, i, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+        }
+    }
+
+    /* print ranks */
+    if (rank == 0) {
+        printf("Transfer took %lfs\n", MPI_Wtime() - before_time);
+        printf("The MPI_COMM_WORLD ranks are:\n");
+        for (int i = 0; i < size; i++) {
+            printf("%d ", ranks[i]);
+        }
+        printf("\n");
+    }
+
+    MPI_Finalize();
+    return 0;
+}

D4-MPI/03-MPI-Collective-Comms/demo/reduce.c

+#include <stdio.h>
+#include <mpi.h>
+
+int main(int argc, char *argv[]) {
+    MPI_Init(&argc, &argv);
+
+    int rank, size;
+
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+    int rank_sum = 0;
+
+    double before_time = MPI_Wtime();
+    /* collect ranks at root and add to running sum */
+    if (rank > 0) {
+        MPI_Send(&rank, 1, MPI_INT, 0, rank, MPI_COMM_WORLD);
+    } else {
+        int recv_rank;
+        for (int i = 1; i < size; i++) {
+            MPI_Recv(&recv_rank, 1, MPI_INT, i, i, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+            rank_sum += recv_rank;
+        }
+    }
+
+    /* print ranks */
+    if (rank == 0) {
+        printf("Sum took %lfs\n", MPI_Wtime() - before_time);
+        printf("The sum of MPI_COMM_WORLD ranks is %d\n", rank_sum);
+    }
+
+    MPI_Finalize();
+    return 0;
+}