Merge pull request darpanjbora#119 from shanvijha30/SRTF

darpanjbora · web-flow · commit 24b2a6a2a9bd · 2022-10-13T22:14:57.000+05:30
Shortest Remaining Time First (SRTF)
diff --git a/Operating Systems/SRTF.java b/Operating Systems/SRTF.java
@@ -0,0 +1,149 @@
+// Java program to implement Shortest Remaining Time First
+// Shortest Remaining Time First (SRTF)
+
+class Process
+{
+	int pid; // Process ID
+	int bt; // Burst Time
+	int art; // Arrival Time
+	
+	public Process(int pid, int bt, int art)
+	{
+		this.pid = pid;
+		this.bt = bt;
+		this.art = art;
+	}
+}
+
+public class SRTF
+{
+	// Method to find the waiting time for all
+	// processes
+	static void findWaitingTime(Process proc[], int n,
+									int wt[])
+	{
+		int rt[] = new int[n];
+	
+		// Copy the burst time into rt[]
+		for (int i = 0; i < n; i++)
+			rt[i] = proc[i].bt;
+	
+		int complete = 0, t = 0, minm = Integer.MAX_VALUE;
+		int shortest = 0, finish_time;
+		boolean check = false;
+	
+		// Process until all processes gets
+		// completed
+		while (complete != n) {
+	
+			// Find process with minimum
+			// remaining time among the
+			// processes that arrives till the
+			// current time`
+			for (int j = 0; j < n; j++)
+			{
+				if ((proc[j].art <= t) &&
+				(rt[j] < minm) && rt[j] > 0) {
+					minm = rt[j];
+					shortest = j;
+					check = true;
+				}
+			}
+	
+			if (check == false) {
+				t++;
+				continue;
+			}
+	
+			// Reduce remaining time by one
+			rt[shortest]--;
+	
+			// Update minimum
+			minm = rt[shortest];
+			if (minm == 0)
+				minm = Integer.MAX_VALUE;
+	
+			// If a process gets completely
+			// executed
+			if (rt[shortest] == 0) {
+	
+				// Increment complete
+				complete++;
+				check = false;
+	
+				// Find finish time of current
+				// process
+				finish_time = t + 1;
+	
+				// Calculate waiting time
+				wt[shortest] = finish_time -
+							proc[shortest].bt -
+							proc[shortest].art;
+	
+				if (wt[shortest] < 0)
+					wt[shortest] = 0;
+			}
+			// Increment time
+			t++;
+		}
+	}
+	
+	// Method to calculate turn around time
+	static void findTurnAroundTime(Process proc[], int n,
+							int wt[], int tat[])
+	{
+		// calculating turnaround time by adding
+		// bt[i] + wt[i]
+		for (int i = 0; i < n; i++)
+			tat[i] = proc[i].bt + wt[i];
+	}
+	
+	// Method to calculate average time
+	static void findavgTime(Process proc[], int n)
+	{
+		int wt[] = new int[n], tat[] = new int[n];
+		int total_wt = 0, total_tat = 0;
+	
+		// Function to find waiting time of all
+		// processes
+		findWaitingTime(proc, n, wt);
+	
+		// Function to find turn around time for
+		// all processes
+		findTurnAroundTime(proc, n, wt, tat);
+	
+		// Display processes along with all
+		// details
+		System.out.println("Processes " +
+						" Burst time " +
+						" Waiting time " +
+						" Turn around time");
+	
+		// Calculate total waiting time and
+		// total turnaround time
+		for (int i = 0; i < n; i++) {
+			total_wt = total_wt + wt[i];
+			total_tat = total_tat + tat[i];
+			System.out.println(" " + proc[i].pid + "\t\t"
+							+ proc[i].bt + "\t\t " + wt[i]
+							+ "\t\t" + tat[i]);
+		}
+	
+		System.out.println("Average waiting time = " +
+						(float)total_wt / (float)n);
+		System.out.println("Average turn around time = " +
+						(float)total_tat / (float)n);
+	}
+	
+	// Driver Method
+	public static void main(String[] args)
+	{
+		Process proc[] = { new Process(1, 6, 1),
+							new Process(2, 8, 1),
+							new Process(3, 7, 2),
+							new Process(4, 3, 3)};
+		
+		findavgTime(proc, proc.length);
+	}
+}
+
