implemented priority scheduling

simulator.c

@@ -8,6 +8,7 @@
 enum pstate {
     WAITING,
     READY,
+    RUNNING,
     FINISHED
 };
 
@@ -18,13 +19,25 @@ struct pinfo {
     int priority;
     
     int wait_time;
-    int completion_time;
+    int turnaround_time;
     int remaining_time;
+    int n_preempted;
     enum pstate state;
 
     struct pinfo * next_pinfo;
 };
 
+int n_processes(struct pinfo * head) {
+    int n = 0;
+
+    while (head != NULL) {
+        n++;
+        head = head->next_pinfo;
+    }
+
+    return n;
+}
+
 struct perf_info {
     int total_time;
     int total_nr_ctxt_switch;
@@ -44,7 +57,7 @@ void print_pinfo(struct pinfo * info) {
     printf("  Execution time: %d\n", info->execution_time);
     printf("  Priority: %d\n", info->priority);
     printf("  Wait time: %d\n", info->wait_time);
-    printf("  Completion time: %d\n", info->completion_time);
+    printf("  Turnaround time: %d\n", info->turnaround_time);
     printf("  Remaining time: %d\n", info->remaining_time);
     printf("  NEXT -> %p\n", info->next_pinfo);
     printf("}>\n");
@@ -64,8 +77,9 @@ struct pinfo * create_process(int id, int arrival_time, int execution_time, int
     info->execution_time = execution_time;
     info->priority = priority;
     info->wait_time = 0;
-    info->completion_time = 0;
+    info->turnaround_time = 0;
     info->remaining_time = execution_time;
+    info->n_preempted = 0;
     info->state = WAITING;
     info->next_pinfo = NULL;
     return info;
@@ -83,8 +97,8 @@ struct perf_info schedule_FCFS(struct pinfo * processes) {
             wait_time = 0;
         }
         process->wait_time = wait_time;
-        process->completion_time = process->execution_time + process->wait_time;
+        process->turnaround_time = process->execution_time + process->wait_time;
-        current_time = process->arrival_time + process->completion_time;
+        current_time = process->arrival_time + process->turnaround_time;
 
         process = process->next_pinfo;
     }
@@ -93,6 +107,201 @@ struct perf_info schedule_FCFS(struct pinfo * processes) {
     return perf;
 }
 
+struct prio_list {
+    struct pinfo ** proc;
+    int length;
+};
+
+/**
+ * Pops and returns the last element (highest priority) of the given priority list
+ * 
+ * Returns NULL if the list is empty
+ */
+struct pinfo * prio_list_pop(struct prio_list * list) {
+    if (list->length == 0) {
+        return NULL;
+    }
+
+    list->length--;
+    return *(list->proc + list->length);
+}
+
+/**
+ * Adds the given process in the priority list at
+ * the appropriate place (according to its priority)
+ */
+void prio_list_add(struct prio_list * list, struct pinfo * proc) {
+    struct pinfo * proc2;
+    int idx = 0;
+
+    // Find first element (from the right) with lower priority
+    for (int i=list->length-1; i>=0; i--) {
+        proc2 = *(list->proc + i);
+        if (proc2->priority > proc->priority) {
+            idx = i+1;
+            break;
+        }
+    }
+    // Shift elements
+    for (int j=list->length-1; j>=idx; j--) {
+        *(list->proc + j + 1) = *(list->proc + j);
+    }
+    *(list->proc + idx) = proc;
+    list->length++;
+}
+
+/**
+ * Creates a new priority list
+ */
+struct prio_list * create_prio_list(int max_size) {
+    struct pinfo ** processes = (struct pinfo **) malloc(sizeof(struct pinfo *) * max_size);
+    struct prio_list * list = (struct prio_list *) malloc(sizeof(struct prio_list));
+    list->length = 0;
+    list->proc = processes;
+    return list;
+}
+
+/**
+ * Returns the last element (highest priority) of the given priority list
+ */
+struct pinfo * prio_list_last(struct prio_list * list) {
+    return *(list->proc + list->length - 1);
+}
+
+/**
+ * Prints the pids of the processes in the given priority list
+ */
+void prio_list_print(struct prio_list * list) {
+    printf("queue: ");
+    for (int i=0; i < list->length; i++) {
+        if (i != 0) {
+            printf(", ");
+        }
+        printf("%d", (*(list->proc + i))->id);
+    }
+    printf("\n");
+}
+
+struct perf_info schedule_Pr(struct pinfo * processes) {
+    struct perf_info perf = {0, 0, 0};
+
+    int current_time = 0;
+    struct pinfo * current = NULL;
+    struct pinfo * next = processes;
+
+    int N = n_processes(processes);
+    printf("N = %d\n", N);
+
+    struct prio_list * queue = create_prio_list(N);
+    
+    int finished = 0;
+
+    while (finished != N) {
+        printf("\nCurrent time: %d / ", current_time);
+        if (current != NULL) {
+            printf("Current: %d / ", current->id);
+        } else {
+            printf("Current: none / ");
+        }
+        if (next != NULL) {
+            printf("Next: %d\n", next->id);
+        } else {
+            printf("Next: none\n");
+        }
+
+        if (current == NULL) {
+            printf("No running process: running %d\n", next->id);
+            current = next;
+            current->state = RUNNING;
+            next = next->next_pinfo;
+        
+        } else if (next != NULL) {
+            next->state = READY;
+            prio_list_print(queue);
+            printf("Processing next process (%d)\n", next->id);
+
+            // If current finished before next
+            while (current != NULL && current_time + current->remaining_time <= next->arrival_time) {
+                printf("  Process %d finished before next\n", current->id);
+                current->state = FINISHED;
+                current_time += current->remaining_time;
+                current->turnaround_time = current_time - current->arrival_time;
+                current->remaining_time = 0;
+                finished++;
+                current = prio_list_pop(queue);
+            }
+
+            if (current != NULL) {
+                printf("Removing time from current process\n");
+                current->remaining_time -= next->arrival_time - current_time;
+                current->turnaround_time += next->arrival_time - current_time;
+            }
+            if (next->arrival_time > current_time) {
+                current_time = next->arrival_time;
+            }
+            next->state = READY;
+
+            // If no running process, immediately run next process
+            if (current == NULL) {
+                printf("Queue is empty, running next process %d\n", next->id);
+                current = next;
+                current->state = RUNNING;
+                next = next->next_pinfo;
+
+            } else if (next->priority < current->priority) {
+                // Preempt current process
+                printf("Next process (%d) has higher priority\n", next->id);
+                if (current->state == RUNNING) {
+                    printf("  Preempting current process (%d)\n", current->id);
+                    current->n_preempted++;
+                    current_time += CNTXT_SWITCH;
+                    perf.total_nr_ctxt_switch++;
+                }
+                current->state = READY;
+                prio_list_add(queue, current);
+
+                // Run process with higher priority
+                current = next;
+                current->state = RUNNING;
+                next = next->next_pinfo;
+            } else {
+                printf("Adding next process (%d) to list\n", next->id);
+                prio_list_add(queue, next);
+                next = next->next_pinfo;
+            }
+            if (current != NULL) {
+                current->state = RUNNING;
+            }
+
+            
+        } else {
+            printf("No new processes, emptying queue\n");
+            while (current != NULL) {
+                printf("Completing process %d\n", current->id);
+                current->state = FINISHED;
+                current_time += current->remaining_time;
+                current->turnaround_time = current_time - current->arrival_time;
+                current->remaining_time = 0;
+                finished++;
+                current = prio_list_pop(queue);
+                if (current != NULL) {
+                    current->state = RUNNING;
+                }
+            }
+        }
+    }
+    perf.total_time = current_time;
+    perf.total_time_ctxt_switch = perf.total_nr_ctxt_switch * CNTXT_SWITCH;
+
+    return perf;
+}
+
+void compute_waiting_time(struct pinfo * processes) {
+    while (processes != NULL) {
+        processes->wait_time = processes->turnaround_time - processes->execution_time;
+        processes = processes->next_pinfo;
+    }
+}
 
 struct pinfo * read_file() {
     FILE * file = fopen("tasks.csv", "r");
@@ -154,7 +363,10 @@ void free_processes(struct pinfo * next) {
 int main() {
     struct pinfo * processes = read_file();
 
-    struct perf_info perf = schedule_FCFS(processes);
+    //struct perf_info perf = schedule_FCFS(processes);
+    struct perf_info perf = schedule_Pr(processes);
+
+    compute_waiting_time(processes);
 
     //write_file(processes, &perf);
     print_processes(processes);