Merge pull request #10 from Zard-C/lec18_example_code

add IceCreamStore Example

Examples/IceCreamStore/ice_cream_store_simulation.c

@@ -0,0 +1,205 @@
+#include <pthread.h>
+#include <semaphore.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/*
+    This example is a simulation of an ice cream store introduced in cs107 course at Stanford University.
+    The store has a limited number of cones and scoops. The store has a limited number of customers.
+    The store has a limited number of employees. The store has a limited number of cashiers.
+*/
+
+/*
+    Since we don't have cs107 library, we use posix threads and semaphores to simulate the ice cream store.
+*/
+
+// global variables
+struct Inspection
+{
+    bool passed;
+    sem_t requested;
+    sem_t finished; // granted is a better name
+    sem_t lock;
+} inspection;
+
+// a FIFO queue
+struct Line
+{
+    int number; // init as 0, increment by 1
+    sem_t requested;
+    sem_t customers[10];
+    sem_t lock;
+} line;
+
+// a barrier to run all threads
+pthread_barrier_t barrier;
+
+void *clerk(void *arg);
+
+void *customer(void *arg)
+{
+    int numCones = *(int *)arg;
+
+    sem_t clerkSDone;
+    sem_init(&clerkSDone, 0, 0);
+
+    // wait for the barrier
+    pthread_barrier_wait(&barrier);
+
+    pthread_t clerkThreads[4];
+
+    for (int i = 0; i < numCones; i++)
+    {
+        pthread_create(&clerkThreads[i], NULL, clerk, &clerkSDone);
+        printf("Customer %lu is waiting for clerk to make cone %d\n", pthread_self(), i);
+    }
+
+    for (int i = 0; i < numCones; i++)
+    {
+        sem_wait(&clerkSDone);
+        printf("Customer %lu has received cone %d\n", pthread_self(), i);
+    }
+    for (int i = 0; i < numCones; i++)
+    {
+        pthread_join(clerkThreads[i], NULL);
+    }
+
+    sem_destroy(&clerkSDone);
+
+    // Walk to the cashier
+    printf("Customer %lu is walking to the cashier\n", pthread_self());
+    sem_wait(&line.lock);
+    int position = line.number++; // get the position in line
+    sem_post(&line.lock);
+
+    printf("Customer %lu is at position %d in line\n", pthread_self(), position);
+    sem_post(&line.requested);
+    sem_wait(&line.customers[position]); // wait for the cashier to checkout
+    printf("Customer %lu is done\n", pthread_self());
+    return NULL;
+}
+
+void *clerk(void *arg)
+{
+    // sem_t semToSignal = *(sem_t *)arg;
+
+    // make cones until passing inspection
+
+    bool passed = false;
+    while (!passed)
+    {
+        // Make a cone
+        sem_wait(&inspection.lock);
+        sem_post(&inspection.requested);
+        sem_wait(&inspection.finished);
+        passed = inspection.passed;
+        sem_post(&inspection.lock);
+    }
+
+    // give the cone to customer
+    printf("Clerk %lu has made a cone\n", pthread_self());
+    sem_post((sem_t *)arg);
+
+    return NULL;
+}
+
+void *manager(void *arg)
+{
+    int totalConesNeeded = *(int *)arg;
+    int numApproved = 0;
+    int numInspected = 0;
+
+    // wait for the barrier
+    pthread_barrier_wait(&barrier);
+
+    while (numApproved < totalConesNeeded)
+    {
+        sem_wait(&inspection.requested);
+        numInspected++;
+        inspection.passed = rand() % 2;
+        if (inspection.passed == true)
+        {
+            numApproved++;
+        }
+        sem_post(&inspection.finished);
+    }
+
+    return NULL;
+}
+
+void *cashier(void *arg)
+{
+    (void)arg;
+
+    // wait for the barrier
+    pthread_barrier_wait(&barrier);
+
+    // there a total 10 customers in this simulation
+    for (int i = 0; i < 10; i++)
+    {
+        sem_wait(&line.requested);
+        // checkout the customer
+        sem_post(&line.customers[i]);
+    }
+
+    return NULL;
+}
+
+void Initialize()
+{
+    sem_init(&inspection.requested, 0, 0);
+    sem_init(&inspection.finished, 0, 0);
+    sem_init(&inspection.lock, 0, 1);
+
+    sem_init(&line.requested, 0, 0);
+    sem_init(&line.lock, 0, 1);
+    line.number = 0;
+}
+
+int main(int argc, char **argv)
+{
+    int totalCones = 0;
+    srand(time(NULL));
+    Initialize();
+
+    // set a pthread attr to create a detached thread
+    pthread_attr_t attr;
+    pthread_attr_init(&attr);
+
+    pthread_t customers[10];
+    int cones[10];
+    for (int i = 0; i < 10; i++)
+    {
+        cones[i] = rand() % 4 + 1;
+        totalCones += cones[i];
+    }
+
+    pthread_barrier_init(&barrier, NULL, 12); // 10 customers, 1 manager, 1 cashier (12 threads in total
+
+    for (int i = 0; i < 10; i++)
+    {
+        pthread_create(&customers[i], &attr, customer, &cones[i]);
+    }
+
+    pthread_t managerThread;
+    pthread_create(&managerThread, NULL, manager, &totalCones);
+
+    pthread_t cashierThread;
+    pthread_create(&cashierThread, NULL, cashier, NULL);
+
+    // Run all threads, how to implement this?
+
+    // wait for all customers to finish
+    for (int i = 0; i < 10; i++)
+    {
+        pthread_join(customers[i], NULL);
+    }
+    pthread_join(managerThread, NULL);
+    pthread_join(cashierThread, NULL);
+    pthread_barrier_destroy(&barrier);
+    printf("Done simulation\n");
+
+    return 0;
+}