Black-White Bakery Algorithm

Definition of Black-White Bakery Algorithm

The Black-White Bakery Algorithm is a variation of the original Bakery Algorithm, used in computer science for achieving mutual exclusion among processes in a distributed system. Unlike the original method, it employs two distinct types of tokens (black and white) to achieve synchronization. This modification improves the system’s performance by reducing the waiting time for processes while still ensuring that no two processes can enter a critical section simultaneously.


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Key Takeaways

  1. The Black-White Bakery Algorithm is a modification of Lamport’s Bakery Algorithm that reduces the number of shared variables and simplifies checking for priority before entering a critical section.
  2. The algorithm works with two types of processes, Black and White, alternating between them for entering the critical section and avoiding starvation. Each process is assigned a unique number to determine the priority.
  3. It employs a token-based system and uses a boolean flag to indicate if a process is in a critical section or not. This design improves efficiency and synchronization between concurrent processes while ensuring mutual exclusion and fairness.

Importance of Black-White Bakery Algorithm

The Black-White Bakery Algorithm is an important concept in computer science because it offers a solution to the critical section problem in concurrent programming, ensuring that the processes execute their critical sections in a mutually exclusive manner.

Developed by Leslie Lamport in 1974, the algorithm aims to achieve synchronization among multiple threads, regardless of the number of available resources, by providing a simple and elegant “first-come, first-served” mechanism.

It ensures fairness and prevents issues like deadlock, livelock, and starvation, leading to increased efficiency and improved performance in computer systems.

The Black-White Bakery Algorithm has greatly impacted the development of distributed systems and the understanding of concurrency control, making it a fundamental subject in the field of computer science.


The Black-White Bakery Algorithm plays a crucial role in the world of computer science, particularly when it comes to achieving synchronization among multiple processes in a distributed system. Serving as a metaphorical bakery where customers (processes) receive a ticket (number) to ensure their fair turn in receiving service, the algorithm effectively addresses the challenges of mutual exclusion, a concept vital to the prevention of concurrent usage of a shared resource by multiple processes.

Invented by computer scientist, Edsger W. Dijkstra, the algorithm ensures that processes are granted access to the shared resource in a manner that is orderly and follows a strict sequence, leading to improved overall system performance and enhanced reliability.

One of the key aspects of the Black-White Bakery Algorithm is its ability to identify and differentiate between two classes of processes – black and white. In doing so, the algorithm increases efficiency and guarantees a higher level of fairness during execution.

Processes are assigned in a manner that prevents them from indefinitely waiting for access to the shared resource, reducing the risk of potential deadlocks and enabling high priority tasks to be completed in a timely fashion. By accurately determining the sequence in which processes are allowed to use the shared resource, the Black-White Bakery Algorithm ensures smooth functioning of distributed systems, laying the foundation for a harmonious and dependable computing environment.

Examples of Black-White Bakery Algorithm

The Black-White Bakery Algorithm, developed by Leslie Lamport, is a_mutex algorithm used primarily to prevent race conditions in a distributed computing system and ensuring mutual exclusion among processes. While real-world “products” based on this algorithm might not be advertised directly as such, there are several applications where distributed systems can use the Black-White Bakery Algorithm as a part of their synchronization methods. Here are three examples:

Distributed databases: In a distributed database system, multiple servers store and manage the database to ensure high availability, scalability, and fault tolerance. When different servers need to access the same data for updates or modifications, the Black-White Bakery Algorithm can be applied to ensure mutually exclusive access to the data and avoid any potential race conditions.

Blockchain systems: Blockchains, like Bitcoin and Ethereum, often rely on decentralized networks to achieve consensus between nodes and validate transactions. These systems need an efficient way to ensure mutual exclusion among nodes in order to prevent double-spending or transaction failures. The Black-White Bakery Algorithm can be employed in distributed consensus mechanisms to provide this functionality.

Cloud computing resource allocation: In the cloud computing scenario, a large number of virtual servers run on physical machines. To manage resources like CPU, memory, and storage effectively, and ensure fair access among these virtual servers, the Black-White Bakery Algorithm can be used to control and prioritize resource allocation in a distributed system.

Black-White Bakery Algorithm FAQ

1. What is the Black-White Bakery Algorithm?

The Black-White Bakery Algorithm is a modified version of the original Bakery Algorithm, which is used to manage concurrent processes in a distributed system. In this algorithm, processes are assigned binary identifiers (black or white), allowing the algorithm to resolve conflicts and maintain synchronization among these processes.

2. Who developed the Black-White Bakery Algorithm?

The Black-White Bakery Algorithm was developed by Leslie Lamport, who is a renowned computer scientist and the creator of the original Bakery Algorithm.

3. How does the Black-White Bakery Algorithm work?

In the Black-White Bakery Algorithm, each process is assigned a binary identifier – either black or white. When a process requires access to a shared resource, it applies a “bakery-style ticket,” based on its identifier and priority. The algorithm then compares the ticket values, ensuring that the processes with higher priority are granted access to the shared resource first. In case of a tie, the binary identifier is used to break the deadlock.

4. What are the advantages of the Black-White Bakery Algorithm over the original Bakery Algorithm?

The Black-White Bakery Algorithm simplifies the implementation of the original Bakery Algorithm by using binary identifiers. It reduces the complexity and provides a more efficient resolution of deadlocks, ensuring that the processes are synchronized effectively.

5. What are some applications of the Black-White Bakery Algorithm?

The Black-White Bakery Algorithm has found its applications in various areas of computer science, particularly in distributed systems, operating systems, and concurrent programming. It is used to manage access to shared resources and ensure synchronization among processes in these fields.

Related Technology Terms

  • Mutual Exclusion
  • Concurrency Control
  • Distributed Systems
  • Shared Resources
  • Critical Section

Sources for More Information


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