Round Robin Calculator – Loan calculator

Round Robin Scheduling Calculator

Use this calculator to simulate the Round Robin CPU scheduling algorithm and determine key performance metrics for a set of processes.

Time Quantum:

The fixed time slice (in time units) allocated to each process before preemption.

Processes:

.calculator-container { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 20px; border-radius: 8px; box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); max-width: 800px; margin: 20px auto; color: #333; } .calculator-container h2, .calculator-container h3, .calculator-container h4 { color: #0056b3; border-bottom: 2px solid #e0e0e0; padding-bottom: 10px; margin-top: 20px; } .calculator-inputs label { display: inline-block; margin-bottom: 5px; font-weight: bold; width: 120px; } .calculator-inputs input[type="number"] { width: 80px; padding: 8px; margin-bottom: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; } .calculator-inputs .description { font-size: 0.9em; color: #666; margin-top: -5px; margin-bottom: 15px; padding-left: 130px; /* Align with input fields */ } .process-row { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; padding: 8px; background-color: #eef7ff; border-radius: 4px; border: 1px solid #d0e9ff; } .process-row label { width: auto; /* Override general label width for process rows */ min-width: 70px; font-weight: normal; } .process-row input[type="number"] { width: 60px; margin-bottom: 0; } .calculator-inputs button { background-color: #007bff; color: white; padding: 10px 15px; border: none; border-radius: 4px; cursor: pointer; font-size: 16px; margin-top: 10px; margin-right: 10px; transition: background-color 0.2s ease; } .calculator-inputs button:hover { background-color: #0056b3; } .process-row button { background-color: #dc3545; padding: 5px 10px; font-size: 14px; margin-top: 0; } .process-row button:hover { background-color: #c82333; } .calculator-results { margin-top: 30px; padding-top: 20px; border-top: 2px solid #e0e0e0; } .calculator-results table { width: 100%; border-collapse: collapse; margin-top: 15px; } .calculator-results table th, .calculator-results table td { border: 1px solid #ddd; padding: 8px; text-align: center; } .calculator-results table th { background-color: #f2f2f2; font-weight: bold; } .calculator-results p { font-size: 1.1em; margin-bottom: 5px; } .calculator-results pre { background-color: #eee; padding: 10px; border-radius: 4px; overflow-x: auto; white-space: pre-wrap; word-wrap: break-word; } var processCounter = 0; // Use a simple counter for unique input IDs function addProcessRow() { processCounter++; var container = document.getElementById("processInputsContainer"); var newRow = document.createElement("div"); newRow.className = "process-row"; newRow.innerHTML = ` Process P${processCounter}: Arrival Time Burst Time `; container.appendChild(newRow); } function removeProcessRow(buttonElement) { var rowToRemove = buttonElement.parentNode; rowToRemove.parentNode.removeChild(rowToRemove); } // Initial processes for a good example addProcessRow(); // P1 document.getElementById("arrivalTime_P1").value = "0"; document.getElementById("burstTime_P1").value = "5"; addProcessRow(); // P2 document.getElementById("arrivalTime_P2").value = "1"; document.getElementById("burstTime_P2").value = "3"; addProcessRow(); // P3 document.getElementById("arrivalTime_P3").value = "2"; document.getElementById("burstTime_P3").value = "2"; document.getElementById("timeQuantum").value = "2"; function calculateRoundRobin() { var timeQuantum = parseInt(document.getElementById("timeQuantum").value); if (isNaN(timeQuantum) || timeQuantum <= 0) { document.getElementById("roundRobinResult").innerHTML = "Please enter a valid positive Time Quantum."; return; } var processes = []; var processRows = document.getElementById("processInputsContainer").children; if (processRows.length === 0) { document.getElementById("roundRobinResult").innerHTML = "Please add at least one process."; return; } for (var i = 0; i < processRows.length; i++) { var processRow = processRows[i]; // Extract the P-number from the label to use for display var labelText = processRow.querySelector('label').innerText; var displayId = parseInt(labelText.replace('Process P', '').replace(':', '')); var arrivalTime = parseInt(processRow.querySelector('[id^="arrivalTime_P"]').value); var burstTime = parseInt(processRow.querySelector('[id^="burstTime_P"]').value); if (isNaN(arrivalTime) || arrivalTime < 0 || isNaN(burstTime) || burstTime <= 0) { document.getElementById("roundRobinResult").innerHTML = "Please enter valid non-negative Arrival Time and positive Burst Time for all processes."; return; } processes.push({ id: i, // Internal ID, corresponds to its index in the 'processes' array displayId: displayId, // ID for display (P1, P2, etc.) arrivalTime: arrivalTime, burstTime: burstTime, originalBurstTime: burstTime, // Keep original for turnaround/waiting time calculation remainingBurstTime: burstTime, completionTime: 0, waitingTime: 0, turnaroundTime: 0, responseTime: -1, // -1 indicates not yet started firstExecutionTime: -1 // To calculate response time }); } var n = processes.length; var currentTime = 0; var completedProcesses = 0; var readyQueue = []; // Stores internal process IDs (0 to n-1) var results = new Array(n); // To store results for display in original order var ganttChart = []; while (completedProcesses < n) { // Step 1: Add all processes that have arrived by currentTime and are not yet in the readyQueue // and have remaining burst time. for (var i = 0; i < n; i++) { if (processes[i].arrivalTime 0 && readyQueue.indexOf(processes[i].id) === -1) { readyQueue.push(processes[i].id); } } // Step 2: If ready queue is empty, advance time to the next arrival if (readyQueue.length === 0) { var nextArrivalTime = Infinity; var foundUnarrived = false; for (var i = 0; i 0 && processes[i].arrivalTime > currentTime) { foundUnarrived = true; if (processes[i].arrivalTime < nextArrivalTime) { nextArrivalTime = processes[i].arrivalTime; } } } if (!foundUnarrived) { // All processes either completed or arrived and are in queue break; // All processes are done or stuck } if (nextArrivalTime !== Infinity) { currentTime = nextArrivalTime; continue; // Re-evaluate queue with new current time } else { break; // Should not happen } } // Step 3: Dequeue a process var currentProcessId = readyQueue.shift(); var currentProcess = processes[currentProcessId]; if (currentProcess.firstExecutionTime === -1) { currentProcess.firstExecutionTime = currentTime; } var executionTime = Math.min(currentProcess.remainingBurstTime, timeQuantum); ganttChart.push({ processId: currentProcess.displayId, // Use displayId for Gantt chart start: currentTime, end: currentTime + executionTime }); currentTime += executionTime; currentProcess.remainingBurstTime -= executionTime; // Step 4: After execution, add any *newly* arrived processes to the ready queue // This is crucial for Round Robin. Processes arriving during execution should be added. for (var i = 0; i < n; i++) { if (processes[i].arrivalTime 0 && readyQueue.indexOf(processes[i].id) === -1) { readyQueue.push(processes[i].id); } } // Step 5: Check if current process completed or needs to be re-queued if (currentProcess.remainingBurstTime === 0) { currentProcess.completionTime = currentTime; currentProcess.turnaroundTime = currentProcess.completionTime – currentProcess.arrivalTime; currentProcess.waitingTime = currentProcess.turnaroundTime – currentProcess.originalBurstTime; currentProcess.responseTime = currentProcess.firstExecutionTime – currentProcess.arrivalTime; completedProcesses++; results[currentProcess.id] = currentProcess; } else { // If not finished, add back to the end of the ready queue readyQueue.push(currentProcess.id); } } var totalWaitingTime = 0; var totalTurnaroundTime = 0; var totalResponseTime = 0; var output = "

Round Robin Scheduling Results

"; output += ""; output += ""; output += ""; for (var i = 0; i < n; i++) { var p = results[i]; totalWaitingTime += p.waitingTime; totalTurnaroundTime += p.turnaroundTime; totalResponseTime += p.responseTime; output += ""; output += ""; // Use displayId here output += ""; output += ""; output += ""; output += ""; output += ""; output += ""; output += ""; } output += "

Process ID	Arrival Time	Burst Time	Completion Time	Turnaround Time	Waiting Time	Response Time
P" + p.displayId + "	" + p.arrivalTime + "	" + p.originalBurstTime + "	" + p.completionTime + "	" + p.turnaroundTime + "	" + p.waitingTime + "	" + p.responseTime + "

"; output += "

Averages:

"; output += "Average Turnaround Time: " + (totalTurnaroundTime / n).toFixed(2) + ""; output += "Average Waiting Time: " + (totalWaitingTime / n).toFixed(2) + ""; output += "Average Response Time: " + (totalResponseTime / n).toFixed(2) + ""; output += "

Gantt Chart:

"; var ganttString = ""; var lastEndTime = 0; for (var i = 0; i lastEndTime) { ganttString += "| Idle (" + lastEndTime + "-" + entry.start + ") "; } ganttString += "| P" + entry.processId + " (" + entry.start + "-" + entry.end + ") "; lastEndTime = entry.end; } ganttString += "|"; output += "" + ganttString + ""; document.getElementById("roundRobinResult").innerHTML = output; }

Understanding Round Robin CPU Scheduling

The Round Robin (RR) scheduling algorithm is a pre-emptive algorithm primarily used for time-sharing operating systems. It's designed to give each process a fair share of CPU time, ensuring that no single process monopolizes the processor. This calculator helps you simulate the Round Robin algorithm and analyze its performance metrics.

How Round Robin Works

In Round Robin scheduling, each process is assigned a fixed time unit called a Time Quantum (or time slice). The CPU scheduler cycles through the ready queue, allocating the CPU to each process for a duration of one time quantum. If a process completes its execution within the time quantum, it's terminated. If it doesn't complete, it's preempted (interrupted) and moved to the end of the ready queue, allowing the next process in the queue to execute.

This cyclic execution ensures that all processes get a chance to run, providing a responsive system, especially for interactive tasks. The choice of time quantum is crucial: a very small quantum leads to frequent context switching overhead, while a very large quantum makes RR behave more like First-Come, First-Served (FCFS).

Key Metrics Explained

Arrival Time (AT): The time at which a process enters the ready queue and becomes available for execution.
Burst Time (BT): The total CPU time required by a process for its complete execution.
Completion Time (CT): The time at which a process finishes its execution.
Turnaround Time (TT): The total time a process spends in the system, from arrival to completion.
Turnaround Time = Completion Time - Arrival Time
Waiting Time (WT): The total time a process spends waiting in the ready queue for the CPU.
Waiting Time = Turnaround Time - Burst Time
Response Time (RT): The time from when a process arrives until it first gets the CPU. This measures the responsiveness of the system.
Response Time = First Execution Time - Arrival Time

Using the Round Robin Calculator

To use the calculator, follow these steps:

Set Time Quantum: Enter the desired time quantum (e.g., 2, 4, 8 time units).
Add Processes: Click "Add Process" to add new rows for each process.
Enter Process Details: For each process, input its:
- Arrival Time: When the process becomes available.
- Burst Time: How much CPU time it needs to complete.
Calculate: Click "Calculate Round Robin" to see the results.

Example Scenario

Let's consider an example with a Time Quantum of 2 units:

Process P1: Arrival Time = 0, Burst Time = 5
Process P2: Arrival Time = 1, Burst Time = 3
Process P3: Arrival Time = 2, Burst Time = 2

Using the calculator with these inputs, you would observe the following (as per the example trace in the thought process):

Gantt Chart: | P1 (0-2) | P2 (2-4) | P3 (4-6) | P1 (6-8) | P2 (8-9) | P1 (9-10) |

Results:

P1: CT=10, TT=10, WT=5, RT=0
P2: CT=9, TT=8, WT=5, RT=1
P3: CT=6, TT=4, WT=2, RT=2

Averages:

Average Turnaround Time: 7.33
Average Waiting Time: 4.00
Average Response Time: 1.00

Benefits and Drawbacks

Benefits:

Fairness: Ensures all processes get a fair share of CPU time.
Responsiveness: Provides good response times for interactive users.
Starvation-Free: No process is left waiting indefinitely.

Drawbacks:

Context Switching Overhead: Frequent context switching can reduce overall CPU efficiency, especially with a small time quantum.
Performance Dependency on Quantum: Performance is highly dependent on the chosen time quantum.
Higher Turnaround Time: Can result in higher average turnaround times compared to non-preemptive algorithms for batch processes.

The Round Robin calculator is a valuable tool for students and professionals to understand and analyze the behavior of this fundamental CPU scheduling algorithm.