🏦 Banker's Algorithm — Deadlock Avoidance Simulator

Operating Systems Project · Python · Streamlit

---

📌 Overview

This project simulates the Banker's Algorithm, a classic deadlock avoidance technique in Operating Systems, proposed by Edsger W. Dijkstra in 1965. The simulator allows you to interactively enter system state data, run the safety algorithm step-by-step, and visualize whether a system is in a safe or unsafe state.

The name "Banker's Algorithm" comes from its analogy to banking — just as a bank only grants loans if it can still serve all remaining customers, an OS only allocates resources if the system remains in a safe state afterward.

---

🎯 What This Simulator Does

The simulator acts as a mini operating system decision engine. Given a set of processes and resource types, it answers:

"If I allocate resources to these processes in this state — will the system ever get stuck?"

• If YES, it can finish all processes safely → System is in a SAFE STATE ✅
• If NO, some process will be permanently blocked → System is in an UNSAFE STATE ❌

---

🧠 Algorithm Explanation

Data Structures Used

Structure	Dimension	Description
Available[j]	1 × m	Free instances of resource type Rⱼ
Max[i][j]	n × m	Maximum demand of process Pᵢ for resource Rⱼ
Allocation[i][j]	n × m	Resources of type Rⱼ currently held by Pᵢ
Need[i][j]	n × m	Remaining demand: Max[i][j] − Allocation[i][j]

Core Formula

Need[i][j] = Max[i][j] − Allocation[i][j]

This tells us how many more resources each process may still request before it finishes.

Safety Algorithm (Pseudocode)

Work  ←  Available                    // copy of free resources
Finish[i] ← False  for all i          // no process finished yet

REPEAT:
    Find process i such that:
        Finish[i] == False
        AND Need[i] ≤ Work             // can complete with current Work

    If found:
        Work      ← Work + Allocation[i]   // process finishes, releases resources
        Finish[i] ← True
        Add i to Safe Sequence

    Else:
        BREAK                          // no eligible process found

If all Finish[i] == True  →  SAFE STATE   ✅
Else                       →  UNSAFE STATE ❌

Time Complexity: O(n² × m)

---

⚠️ Coffman's Four Conditions for Deadlock

Deadlock can only occur if all four of the following conditions hold simultaneously:

1. Mutual Exclusion — At least one resource is non-shareable
2. Hold and Wait — A process holds a resource while waiting for more
3. No Preemption — Resources cannot be forcibly taken away
4. Circular Wait — A circular chain of processes waiting on each other

The Banker's Algorithm prevents deadlock before it happens by ensuring that no resource allocation can ever lead to a state where circular wait is possible.

---

🔐 Safe State vs Unsafe State vs Deadlock

	Safe State	Unsafe State	Deadlock
Definition	A safe execution sequence exists	No guarantee all processes finish	Processes are permanently stuck
Deadlock?	Cannot occur	May occur	Currently occurring
OS Action	Grant request	Deny request	Recovery needed

⚠️ Key Insight: Unsafe ≠ Deadlocked. An unsafe state means deadlock is possible — not guaranteed. The algorithm conservatively denies all requests that could lead to an unsafe state.

---

💻 Features

• Interactive Matrix Input — Enter Allocation, Max, and Available matrices via editable tables
• Live Validation — Catches errors like Allocation > Max before running
• Auto Need Matrix — Computed instantly from Max − Allocation
• Step-by-Step Trace — See every iteration: Work vector, candidates, condition checks, Finish array
• Summary Table — Full simulation in clean tabular form
• Safe/Unsafe Result Banner — Clear colour-coded final verdict
• Built-in Presets — Load classic textbook examples with one click
• Reset Option — Clear all data and start fresh

---

🚀 Installation & Run

# Install dependencies
pip install streamlit pandas numpy 

# Run the simulator
streamlit run app.py

Opens at: http://localhost:8501

---

� Demo

Experience the interactive simulation in action — enter your system state and watch the safety algorithm work step-by-step!

---

�📚 Libraries Used

Library	Purpose
streamlit	Web UI framework and state management
pandas	DataFrame handling and tabular display
numpy	Numerical matrix operations

---

📐 Classic Textbook Example

5 Processes · 3 Resource Types (A, B, C) · Available = [3, 3, 2]

Process	Alloc	Max	Need
P0	[0,1,0]	[7,5,3]	[7,4,3]
P1	[2,0,0]	[3,2,2]	[1,2,2]
P2	[3,0,2]	[9,0,2]	[6,0,0]
P3	[2,1,1]	[2,2,2]	[0,1,1]
P4	[0,0,2]	[4,3,3]	[4,3,1]

Safe Sequence: P1 → P3 → P0 → P2 → P4 ✅

---

Deadlock Avoidance Simulation

Operating Systems · 2026 · Vidyalankar Institute of Technology