files

PSA02/omp_sum_v1.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <omp.h>
+
+int main(int argc, char *argv[]) {
+
+    /* get N and thread_count from command line */
+    if (argc < 3) {
+        printf ("Command usage : %s %s %s\n",argv[0],"N","thread_count");
+        return 1;
+    }
+    long long N = atol(argv[1]);
+    int thread_count = atoi(argv[2]);
+    omp_set_num_threads(thread_count);
+
+    /* start the timer */
+    double start_time, end_time;
+    start_time = omp_get_wtime();
+
+    /* calculate the thread sums in parallel */
+    long long thread_sums[thread_count];
+
+#pragma omp parallel default(none) shared(N,thread_sums)
+    {
+        int thread_num = omp_get_thread_num();
+        thread_sums[thread_num] = 0;
+#pragma omp for
+        for (long long i = 1; i <= N;i++) {
+            thread_sums[thread_num] += i;
+        }
+    }
+
+    /* add the results of the thread_sums */
+    long long sum = 0;
+    for (int i=0;i<thread_count;i++) {
+        sum += thread_sums[i];
+    }    
+
+    /* stop the timer */
+    end_time = omp_get_wtime();
+
+    /* print results */
+    printf ("thread_count = %d, ",thread_count);
+    printf ("elapsed time = %g\n",end_time-start_time);
+    printf (" N = %llu, ",N);
+    printf ("sum = %llu, ",sum);
+    printf ("N*(N+1)/2 = %llu\n",(N/2)*(N+1));
+
+}

PSA02/omp_sum_v1.sh

+#!/bin/bash
+#SBATCH -A cmda3634_rjh
+#SBATCH -p normal_q
+#SBATCH -t 5
+#SBATCH --cpus-per-task=4
+#SBATCH -o omp_sum_v1.out
+
+# Go to the directory where the job was submitted
+cd $SLURM_SUBMIT_DIR
+
+# Load the modules
+module load matplotlib
+
+# Build the executable
+gcc -o omp_sum_v1 omp_sum_v1.c -fopenmp
+
+# OpenMP settings
+export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK
+export OMP_PROC_BIND=true
+
+# run omp_sum
+./omp_sum_v1 200000000 1
+./omp_sum_v1 200000000 2
+./omp_sum_v1 200000000 4

PSA02/omp_sum_v2.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <omp.h>
+
+#define PAD_SIZE 128
+typedef struct thread_sum_s {
+    long long sum;
+    int pad[PAD_SIZE];
+} thread_sum_type;
+
+int main(int argc, char *argv[]) {
+
+    /* get N and thread_count from command line */
+    if (argc < 3) {
+        printf ("Command usage : %s %s %s\n",argv[0],"N","thread_count");
+        return 1;
+    }
+    long long N = atol(argv[1]);
+    int thread_count = atoi(argv[2]);
+    omp_set_num_threads(thread_count);
+
+    /* start the timer */
+    double start_time, end_time;
+    start_time = omp_get_wtime();
+
+    /* calculate the thread sums in parallel */
+    thread_sum_type thread_sums[thread_count];
+
+#pragma omp parallel default(none) shared(N,thread_sums)
+    {
+        int thread_num = omp_get_thread_num();
+        thread_sums[thread_num].sum = 0;
+#pragma omp for
+        for (long long i = 1; i <= N;i++) {
+            thread_sums[thread_num].sum += i;
+        }
+    }
+
+    /* add the results of the thread_sums */
+    long long sum = 0;
+    for (int i=0;i<thread_count;i++) {
+        sum += thread_sums[i].sum;
+    }    
+
+    /* stop the timer */
+    end_time = omp_get_wtime();
+
+    /* print results */
+    printf ("thread_count = %d, ",thread_count);
+    printf ("elapsed time = %g\n",end_time-start_time);
+    printf (" N = %llu, ",N);
+    printf ("sum = %llu, ",sum);
+    printf ("N*(N+1)/2 = %llu\n",(N/2)*(N+1));
+
+}

PSA02/omp_sum_v2.sh

+#!/bin/bash
+#SBATCH -A cmda3634_rjh
+#SBATCH -p normal_q
+#SBATCH -t 5
+#SBATCH --cpus-per-task=4
+#SBATCH -o omp_sum_v2.out
+
+# Go to the directory where the job was submitted
+cd $SLURM_SUBMIT_DIR
+
+# Load the modules
+module load matplotlib
+
+# Build the executable
+gcc -o omp_sum_v2 omp_sum_v2.c -fopenmp
+
+# OpenMP settings
+export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK
+export OMP_PROC_BIND=true
+
+# run omp_sum
+./omp_sum_v2 200000000 1
+./omp_sum_v2 200000000 2
+./omp_sum_v2 200000000 4