Debut t2.

ex2/T1.c

@@ -17,12 +17,40 @@ int main() {
     for(int i = SIZE - 1; i >= 0; i--)
         arr[(SIZE - 1) - i] = i % 2;
 
-    // TODO: Fork another process here
-    // TODO: One process should calculate the median
-    // TODO: The other process should calculate the mean
-    // TODO: Use shm_open, ftruncate, mmap, and munmap to communicate over mapped files
-    // TODO: Print both calculated results and involved PIDs
-    
+    // Use shm_open, ftruncate, mmap, and munmap to communicate over mapped files
+    int fd = open("tmp", O_CREAT|O_RDWR|O_TRUNC, 0666);
+    ftruncate(fd, sizeof(int));
+    float* shm = mmap(NULL, sizeof(float), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+
+    int cpid;
+    // Fork another process here
+    switch (cpid = fork()) {
+        case -1 :
+            perror("error");
+            exit(EXIT_FAILURE);
+        case 0 :
+            // The other process should calculate the mean
+            float sum = 0;
+            for (int i = 0 ; i < SIZE ; i++) {
+                sum += arr[i];
+            }
+            float mean = sum/SIZE;
+            shm[0] = mean;
+            exit(0);
+        default :
+            // One process should calculate the median
+            int status;
+            if (wait(&status) == -1) {
+                perror("error");
+            }
+            sort(arr, SIZE);
+            // Print both calculated results and involved PIDs
+            printf("PID: %d, median: %d\n", getpid(), arr[SIZE/2]);
+            printf("PID: %d, mean: %f\n", cpid, shm[0]);
+            munmap(shm, sizeof(int));
+            close(fd);
+    }
+
     return 0;
 }
 

ex2/T2.c

@@ -5,21 +5,51 @@
 
 #define SIZE 10000
 
+int meanval = 0;
+int medianval = 0;
+
 void swap(int *xp, int *yp);
 void sort(int arr[], int size);
 
 // Function prototypes for thread tasks
-// TODO: Declare functions for calculating mean and median
+void* mean(void* arr) {
+    float sum = 0;
+    for (int i = 0 ; i < SIZE ; i++) {
+        sum += ((int*) arr)[i];
+    }
+    meanval = sum/SIZE;
+    pthread_exit(0);
+}
+
+// Side effect: sorts the array in ascending order
+void* median(void* arr) {
+    sort((int*) arr, SIZE);
+    medianval = ((int*) arr)[SIZE/2];
+    pthread_exit(0);
+}
 
 int main() {
     int arr[SIZE];
     for(int i = SIZE - 1; i >= 0; i--)
         arr[(SIZE - 1) - i] = i % 2;
 
-    // TODO: Implement your solution here
-    // TODO: Create threads for calculating mean and median
-    // TODO: Display the result (mean, median)
-    // TODO: Print TIDs of involved threads
+    // Mean thread:
+    pthread_t tid1;
+    pthread_attr_t attr1;
+    pthread_attr_init(&attr1);
+    pthread_create(&tid1, &attr1, mean, arr);
+
+    // Median thread:
+    pthread_t tid2;
+    pthread_attr_t attr2;
+    pthread_attr_init(&attr2);
+    pthread_create(&tid2, &attr2, median, arr);
+
+    pthread_join(tid1, NULL);
+    pthread_join(tid2, NULL);
+
+    printf("Mean = %d\nMedian = %d\n", meanval, medianval);
+    printf("Mean thread PID: %ld\nMedian thread PID: %ld\n", tid1, tid2);
 
     return 0;
 }