Lab 3 - OpenMP

Multithreading/src/main/java/org/multithreading/ExecuterEX.java

+package org.multithreading;
+
+public class ExecuterEX {
+}

OpenMP/OMP programs/Makefile

+# Makefile 
+
+# Source file
+SRC = $(Pr)
+
+# Compiler
+CC = gcc
+
+# Executable name
+EXE = ./out
+
+all: $(EXE) 
+
+$(EXE): $(SRC)
+	$(CC) -fopenmp -o $(EXE) $(SRC) 
+
+clean:
+	rm -f $(EXE)
+
+run:
+	$(EXE) 

OpenMP/OMP programs/atomic.c

+#include <omp.h>
+#include <stdio.h>
+int main() {
+    int count = 0;
+
+    #pragma omp parallel for num_threads(5)
+    for (int i = 0; i < 100000; i++) {
+	#pragma omp atomic        
+	count++; 
+
+}
+printf("Final count: %d\n", count);
+    return 0;
+}

OpenMP/OMP programs/helloword.c

+#include <omp.h>
+#include <stdio.h>
+
+int main() {
+//    #pragma omp parallel
+//    {
+//        printf("Hello from thread %d\n", omp_get_thread_num());
+//    }
+
+   // Set the number of threads globally for all parallel regions
+    omp_set_num_threads(3);
+
+    // Parallel region with 3 threads (as set by omp_set_num_threads)
+    #pragma omp parallel
+    {
+        printf("Thread with previous set %d out of %d\n", omp_get_thread_num(), omp_get_num_threads());
+    }
+
+    // Parallel region with 5 threads (overrides global setting with num_threads clause)
+    #pragma omp parallel num_threads(5)
+    {
+        printf("Thread %d out of %d\n", omp_get_thread_num(), omp_get_num_threads());
+    }
+
+
+    return 0;
+}

OpenMP/OMP programs/lock.c

+#include <omp.h>
+#include <stdio.h>
+int main() {
+    int count = 0;
+    omp_lock_t lock;
+    // Initialize the lock
+    omp_init_lock(&lock);
+    // Parallel region with lock to control access to 'count'
+    #pragma omp parallel for num_threads(5)
+    for (int i = 0; i < 100000; i++) {
+        // Acquire the lock before modifying 'count'
+       omp_set_lock(&lock);
+        count++;  // Critical section
+       //  Release the lock after modification
+       omp_unset_lock(&lock);
+    }
+
+    // Destroy the lock after use
+    omp_destroy_lock(&lock);
+    printf("Final count: %d\n", count);
+    return 0;
+}

OpenMP/OMP programs/loop.c

+#include <omp.h>
+#include <stdio.h>
+
+int main() {
+    int i;
+    omp_set_num_threads(3);
+    #pragma omp parallel for
+    for(i = 0; i < 10; i++) {
+        printf("Thread %d: i = %d\n", omp_get_thread_num(), i);
+    }
+    return 0;
+}

OpenMP/OMP programs/parallel.c

+#include <stdio.h>
+#include <omp.h>
+
+#define ARRAY_SIZE 1000000  // 1 million elements
+
+int main() {
+    int array[ARRAY_SIZE];
+    long long sum = 0;
+
+    // Initialize array with values
+    for (int i = 0; i < ARRAY_SIZE; i++) {
+        array[i] = i + 1;  // Example: Summing numbers from 1 to ARRAY_SIZE
+    }
+
+    // Measure time for parallel sum
+    double start = omp_get_wtime();
+
+    // Parallel sum calculation
+    #pragma omp parallel for reduction(+:sum) num_threads(5)
+    for (int i = 0; i < ARRAY_SIZE; i++) {
+        sum += array[i];
+    }
+
+    double end = omp_get_wtime();
+    printf("Parallel Sum: %lld\n", sum);
+    printf("Time taken (Parallel): %f seconds\n", end - start);
+
+    return 0;
+}

OpenMP/OMP programs/raceCondition.c

+#include <omp.h>
+#include <stdio.h>
+int main() {
+    int count = 0;
+
+    #pragma omp parallel for num_threads(5)
+    for (int i = 0; i < 100000; i++) {
+        count++;  // Potential race condition
+//  printf("THread Num:%d\n",omp_get_thread_num());
+    
+}    
+printf("Final count: %d\n", count);
+//int x = 2;
+  //  #pragma omp parallel num_threads(6)
+    //{
+     //   int threadId = omp_get_thread_num();
+//
+  //      if (threadId == 0)
+    //        x = 5;
+      //  else
+        //    printf("I am Thread %d and for me x=%d \n", threadId, x);
+   // }
+
+    return 0;
+}	

OpenMP/OMP programs/reduction.c

+#include <omp.h>
+#include <stdio.h>
+
+int main() {
+   int sum = 0;
+
+//#pragma omp parallel for reduction(+:sum)
+    #pragma omp parallel for num_threads(5)
+    for (int i = 0; i < 100000; i++) {
+        sum +=i;  // Potential race condition
+    
+}    
+printf("Final sum: %d\n", sum);
+    return 0;
+}

OpenMP/OMP programs/sequetial.c

+#include <stdio.h>
+#include <omp.h>
+
+#define ARRAY_SIZE 1000000  //  million elements
+
+int main() {
+    int array[ARRAY_SIZE];
+    long long sum = 0;
+
+    // Initialize array with values
+    for (int i = 0; i < ARRAY_SIZE; i++) {
+        array[i] = i + 1;  // Example: Summing numbers from 1 to ARRAY_SIZE
+    }
+
+    // Measure time for sequential sum
+    double start = omp_get_wtime();
+
+    // Sequential sum calculation
+    for (int i = 0; i < ARRAY_SIZE; i++) {
+        sum += array[i];
+    }
+
+    double end = omp_get_wtime();
+    printf("Sequential Sum: %lld\n", sum);
+    printf("Time taken (Sequential): %f seconds\n", end - start);
+
+    return 0;
+}