CPU Scheduling Algorithms

An implementation of various CPU scheduling algorithms in C++. The algorithms include:

• First Come First Serve (FCFS)
• Round Robin (RR)
• Shortest Process Next (SPN)
• Shortest Remaining Time (SRT)
• Highest Response Ratio Next (HRRN)
• Feedback (FB)
• Feedback with varying time quantum (FBV)
• Aging

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📑 Table of Contents

• Algorithms
  • First Come First Serve (FCFS)
  • Round Robin (RR)
  • Shortest Process Next (SPN)
  • Shortest Remaining Time (SRT)
  • Highest Response Ratio Next (HRRN)
  • Feedback (FB)
  • Feedback with varying time quantum (FBV)
  • Aging
• Installation
• Input Format
• Contributors

🧠 Algorithms

->First Come First Serve (FCFS)

Non-preemptive algorithm where the process that arrives first gets executed first. Simple but may cause performance issues if long processes come early.

->Round Robin with varying time quantum (RR)

Preemptive algorithm using time slices (quantum). With varying quantum, it can better balance CPU time across short and long processes.

->Shortest Process Next (SPN)

Non-preemptive algorithm where the process with the shortest burst time is selected next. Reduces average waiting time but can starve longer tasks.

->Shortest Remaining Time (SRT)

Preemptive version of SPN. A running process can be interrupted if a shorter one arrives. Useful when burst time is unknown in advance.

->Highest Response Ratio Next (HRRN)

Non-preemptive. Chooses the process with the highest response ratio, calculated as:

Response Ratio = (Waiting Time + Burst Time) / Burst Time

Favors long-waiting processes, reducing starvation.

->Feedback (FB)

Multi-level preemptive algorithm using priority queues. A process can be demoted to a lower-priority queue after execution.

->Feedback with varying time quantum (FBV)

Same as FB, but each queue uses a different time quantum, allowing for more fine-tuned control.

->Aging

Addresses starvation in priority-based systems by gradually increasing the priority of waiting processes. Ensures that all processes eventually get CPU time.

⚙️ Installation

# Clone the repository
git clone https://github.com/yourusername/CPU-Scheduling-Algorithms.git
cd CPU-Scheduling-Algorithms

# Install compiler tools
sudo apt-get install g++ make

# Build the project
make

# Run the executable
./cpu_scheduling

📥 Input Format

1. Line 1: "trace" or "stats"
2. Line 2: List of scheduling policies with optional parameters (e.g., 2-4 for RR with q=4)
3. Line 3: Integer T – last instant of the simulation
4. Line 4: Number of processes N
5. Next N Lines: Process description

Format per Algorithm:

• For Algorithms 1–7:

  Name, ArrivalTime, ServiceTime
  

• For Algorithm 8 (Aging):

  Name, ArrivalTime, Priority
  

👉 Processes are sorted by arrival time. In case of a tie, the one with the lower priority arrives first.

📎 Check the testcases folder for sample inputs.

👥 Contributors

• @Samyak-Jain-me