Update non_preemptive_sjf_scheduling.cpp

LakshmiSrikumar · LakshmiSrikumar · commit cbbfc88fa9c7 · 2024-10-12T14:38:00.000+05:30
diff --git a/cpu_scheduling_algorithms/non_preemptive_sjf_scheduling.cpp b/cpu_scheduling_algorithms/non_preemptive_sjf_scheduling.cpp
@@ -2,21 +2,22 @@
  * @file
  * @brief Implementation of SJF CPU scheduling algorithm
  * @details
- * shortest job first (SJF), also known as shortest job next (SJN), is a scheduling policy 
- * that selects for execution the waiting process with the smallest execution time.
- * SJN is a non-preemptive algorithm. Shortest remaining time is a preemptive variant of SJN.
+ * shortest job first (SJF), also known as shortest job next (SJN), is a
+ * scheduling policy that selects for execution the waiting process with the
+ * smallest execution time. SJN is a non-preemptive algorithm. Shortest
+ * remaining time is a preemptive variant of SJN.
  * @link https://www.guru99.com/shortest-job-first-sjf-scheduling.html
  * @author [Lakshmi Srikumar](https://github.com/LakshmiSrikumar)
  */
 
-#include <algorithm>         /// for sorting
-#include <cassert>          /// for assert
-#include <random>          /// random number generation  
-#include <iomanip>          /// for formatting the output
-#include <iostream>         /// for IO operations
-#include <queue>            /// for std::priority_queue
-#include <unordered_set>    /// for std::unordered_set
-#include <vector>           /// for std::vector     
+#include <algorithm>      /// for sorting
+#include <cassert>        /// for assert
+#include <iomanip>        /// for formatting the output
+#include <iostream>       /// for IO operations
+#include <queue>          /// for std::priority_queue
+#include <random>         /// random number generation
+#include <unordered_set>  /// for std::unordered_set
+#include <vector>         /// for std::vector
 
 using std::cin;
 using std::cout;
@@ -59,13 +60,14 @@ bool sortcol(tuple<S, T, E>& t1, tuple<S, T, E>& t2) {
 template <typename S, typename T, typename E>
 class Compare {
  public:
-
- /**
+    /**
      * @param t1 First tuple
      * @param t2 Second tuple
      * @brief A comparator function that checks whether to swap the two tuples
      * or not.
-     * <a href="https://www.geeksforgeeks.org/comparator-class-in-c-with-examples/"> detailed description of comparator </a>
+     * <a
+     * href="https://www.geeksforgeeks.org/comparator-class-in-c-with-examples/">
+     * detailed description of comparator </a>
      * @returns true if the tuples SHOULD be swapped
      * @returns false if the tuples SHOULDN'T be swapped
      */
@@ -92,7 +94,7 @@ class Compare {
  */
 template <typename S, typename T, typename E>
 class SJF {
-/**
+    /**
      * Priority queue of schedules(stored as tuples) of processes.
      * In each tuple
      * 1st element: Process ID
@@ -104,16 +106,17 @@ class SJF {
      */
     priority_queue<tuple<S, T, E, double, double, double>,
                    vector<tuple<S, T, E, double, double, double>>,
-                   Compare<S, T, E>> schedule;
-                   
+                   Compare<S, T, E>>
+        schedule;
+
     // Stores final status of all the processes after completing the execution.
     vector<tuple<S, T, E, double, double, double>> result;
-    
+
     // Stores process IDs. Used for confirming absence of a process while  it.
     unordered_set<S> idList;
 
  public:
- /**
+    /**
      * @brief Adds the process to the ready queue if it isn't already there
      * @param id Process ID
      * @param arrival Arrival time of the process
@@ -122,7 +125,7 @@ class SJF {
      *
      */
     void addProcess(S id, T arrival, E burst) {
-    // Add if a process with process ID as id is not found in idList.
+        // Add if a process with process ID as id is not found in idList.
         if (idList.find(id) == idList.end()) {
             tuple<S, T, E, double, double, double> t =
                 make_tuple(id, arrival, burst, 0, 0, 0);
@@ -131,35 +134,39 @@ class SJF {
         }
     }
 
-      /**
-     * @brief Algorithm for scheduling CPU processes according to the Shortest Job
-     First (SJF) scheduling algorithm.
-     *
-     * @details Non pre-emptive SJF is an algorithm that schedules processes based on the length 
-     * of their burst times. The process with the smallest burst time is executed first.
-     * In a non-preemptive scheduling algorithm, once a process starts executing, 
-     * it runs to completion without being interrupted.
-     *
-     * I used a min priority queue because it allows you to efficiently pick the process 
-     * with the smallest burst time in constant time, by maintaining a priority order where 
-     * the shortest burst process is always at the front.
-     *
-     * @returns void
-     */
+    /**
+   * @brief Algorithm for scheduling CPU processes according to the Shortest Job
+   First (SJF) scheduling algorithm.
+   *
+   * @details Non pre-emptive SJF is an algorithm that schedules processes based
+   on the length
+   * of their burst times. The process with the smallest burst time is executed
+   first.
+   * In a non-preemptive scheduling algorithm, once a process starts executing,
+   * it runs to completion without being interrupted.
+   *
+   * I used a min priority queue because it allows you to efficiently pick the
+   process
+   * with the smallest burst time in constant time, by maintaining a priority
+   order where
+   * the shortest burst process is always at the front.
+   *
+   * @returns void
+   */
 
     vector<tuple<S, T, E, double, double, double>> scheduleForSJF() {
-      // Variable to keep track of time elapsed so far
+        // Variable to keep track of time elapsed so far
         double timeElapsed = 0;
 
         while (!schedule.empty()) {
             tuple<S, T, E, double, double, double> cur = schedule.top();
-            
-           // If the current process arrived at time t2, the last process
+
+            // If the current process arrived at time t2, the last process
             // completed its execution at time t1, and t2 > t1.
             if (get<1>(cur) > timeElapsed) {
                 timeElapsed += get<1>(cur) - timeElapsed;
             }
-            
+
             // Add Burst time to time elapsed
             timeElapsed += get<2>(cur);
 
@@ -184,8 +191,8 @@ class SJF {
      * @returns void
      */
 
-    void printResult(const vector<tuple<S, T, E, double, double, double>>& processes) {
-
+    void printResult(
+        const vector<tuple<S, T, E, double, double, double>>& processes) {
         cout << std::setw(17) << left << "Process ID" << std::setw(17) << left
              << "Arrival Time" << std::setw(17) << left << "Burst Time"
              << std::setw(17) << left << "Completion Time" << std::setw(17)
@@ -194,77 +201,80 @@ class SJF {
 
         for (const auto& process : processes) {
             cout << std::setprecision(2) << std::fixed << std::setw(17) << left
-                 << get<0>(process) << std::setw(17) << left
-                 << get<1>(process) << std::setw(17) << left
-                 << get<2>(process) << std::setw(17) << left
-                 << get<3>(process) << std::setw(17) << left
-                 << get<4>(process) << std::setw(17) << left
-                 << get<5>(process) << endl;
+                 << get<0>(process) << std::setw(17) << left << get<1>(process)
+                 << std::setw(17) << left << get<2>(process) << std::setw(17)
+                 << left << get<3>(process) << std::setw(17) << left
+                 << get<4>(process) << std::setw(17) << left << get<5>(process)
+                 << endl;
         }
     }
 };
 
-    /**
-   * @brief Computes the final status of processes after applying non-preemptive SJF scheduling
-   * @tparam S Data type of Process ID
-   * @tparam T Data type of Arrival time
-   * @tparam E Data type of Burst time
-   * @param input A vector of tuples containing Process ID, Arrival time, and Burst time
-   * @returns A vector of tuples containing Process ID, Arrival time, Burst time,
-   *         Completion time, Turnaround time, and Waiting time
-   */
-    template <typename S, typename T, typename E>
-  vector<tuple<S, T, E, double, double, double>> get_final_status(
-      vector<tuple<S, T, E>> input) {
-    
-      // Sort the processes based on Arrival time and then Burst time
-      sort(input.begin(), input.end(), sortcol<S, T, E>);
-
-      // Result vector to hold the final status of each process
-      vector<tuple<S, T, E, double, double, double>> result(input.size());
-      double timeElapsed = 0;
-
-      for (size_t i = 0; i < input.size(); i++) {
+/**
+ * @brief Computes the final status of processes after applying non-preemptive
+ * SJF scheduling
+ * @tparam S Data type of Process ID
+ * @tparam T Data type of Arrival time
+ * @tparam E Data type of Burst time
+ * @param input A vector of tuples containing Process ID, Arrival time, and
+ * Burst time
+ * @returns A vector of tuples containing Process ID, Arrival time, Burst time,
+ *         Completion time, Turnaround time, and Waiting time
+ */
+template <typename S, typename T, typename E>
+vector<tuple<S, T, E, double, double, double>> get_final_status(
+    vector<tuple<S, T, E>> input) {
+    // Sort the processes based on Arrival time and then Burst time
+    sort(input.begin(), input.end(), sortcol<S, T, E>);
+
+    // Result vector to hold the final status of each process
+    vector<tuple<S, T, E, double, double, double>> result(input.size());
+    double timeElapsed = 0;
+
+    for (size_t i = 0; i < input.size(); i++) {
         // Extract Arrival time and Burst time
-          T arrival = get<1>(input[i]);
-          E burst = get<2>(input[i]);
+        T arrival = get<1>(input[i]);
+        E burst = get<2>(input[i]);
 
-          // If the CPU is idle, move time to the arrival of the next process
-          if (arrival > timeElapsed) {
-              timeElapsed = arrival;
-          }
+        // If the CPU is idle, move time to the arrival of the next process
+        if (arrival > timeElapsed) {
+            timeElapsed = arrival;
+        }
 
-          // Update timeElapsed by adding the burst time
-          timeElapsed += burst;
+        // Update timeElapsed by adding the burst time
+        timeElapsed += burst;
 
-          // Calculate Completion time, Turnaround time, and Waiting time
-          double completion = timeElapsed;
-          double turnaround = completion - arrival;
-          double waiting = turnaround - burst;
+        // Calculate Completion time, Turnaround time, and Waiting time
+        double completion = timeElapsed;
+        double turnaround = completion - arrival;
+        double waiting = turnaround - burst;
 
-          // Store the results in the result vector
-          result[i] = make_tuple(get<0>(input[i]), arrival, burst, completion, turnaround, waiting);
-      }
-    
-      return result;
-  }
+        // Store the results in the result vector
+        result[i] = make_tuple(get<0>(input[i]), arrival, burst, completion,
+                               turnaround, waiting);
+    }
+
+    return result;
+}
 
 /**
  * @brief Self-test implementations
  * @returns void
  */
 static void test() {
     // A vector to store the results of all processes across all test cases.
-    vector<tuple<uint32_t, uint32_t, uint32_t, double, double, double>> finalResult;
+    vector<tuple<uint32_t, uint32_t, uint32_t, double, double, double>>
+        finalResult;
 
-    for (int i{}; i < 10; i++) {  
-        std::random_device rd;    // Seeding
+    for (int i{}; i < 10; i++) {
+        std::random_device rd;  // Seeding
         std::mt19937 eng(rd());
-        std::uniform_int_distribution<> distr(1, 10);   
+        std::uniform_int_distribution<> distr(1, 10);
 
-        uint32_t n = distr(eng);  
+        uint32_t n = distr(eng);
         SJF<uint32_t, uint32_t, uint32_t> readyQueue;
-        vector<tuple<uint32_t, uint32_t, uint32_t, double, double, double>> input(n);
+        vector<tuple<uint32_t, uint32_t, uint32_t, double, double, double>>
+            input(n);
 
         // Generate random arrival and burst times
         for (uint32_t i{}; i < n; i++) {
@@ -279,21 +289,19 @@ static void test() {
 
         // Add processes to the queue
         for (uint32_t i{}; i < n; i++) {
-            readyQueue.addProcess(get<0>(input[i]), get<1>(input[i]), get<2>(input[i]));
+            readyQueue.addProcess(get<0>(input[i]), get<1>(input[i]),
+                                  get<2>(input[i]));
         }
 
-        // Perform SJF scheduling
+        // Perform SJF schedulings
         auto finalResult = readyQueue.scheduleForSJF();
 
         // Print processes after scheduling
         cout << "\nProcesses after SJF scheduling:" << endl;
         readyQueue.printResult(finalResult);
     }
     cout << "All the tests have successfully passed!" << endl;
-    }
-
-
-
+}
 
 /**
  * @brief Entry point of the program
