Group Mutual Exclusion in Linear Time and Space

We present two algorithms for the Group Mutual Exclusion (GME) Problem that satisfy the properties of Mutual Exclusion, Starvation Freedom, Bounded Exit, Concurrent Entry and First Come First Served. Both our algorithms use only simple read and write instructions, have O(N) Shared Space complexity and O(N) Remote Memory Reference (RMR) complexity in the Cache Coherency (CC) model. Our first algorithm is developed by generalizing the well-known Lamport's Bakery Algorithm for the classical mutual exclusion problem, while preserving its simplicity and elegance. However, it uses unbounded shared registers. Our second algorithm uses only bounded registers and is developed by generalizing Taubenfeld's Black and White Bakery Algorithm to solve the classical mutual exclusion problem using only bounded shared registers. We show that contrary to common perception our algorithms are the first to achieve these properties with these combination of complexities.Comment: A total of 21 pages including 5 figures and 3 appendices. The bounded shared registers algorithm in the old version has a subtle error (that has no easy fix) necessitating replacement. A correct, but fundamentally different, bounded shared registers algorithm, which has the same properties claimed in the old version is presented in this new version. Also, this version has an additional autho

Constant RMR Group Mutual Exclusion for Arbitrarily Many Processes and Sessions

Group mutual exclusion (GME), introduced by Joung in 1998, is a natural synchronization problem that generalizes the classical mutual exclusion and readers and writers problems. In GME a process requests a session before entering its critical section; processes are allowed to be in their critical sections simultaneously provided they have requested the same session. We present a GME algorithm that (1) is the first to achieve a constant Remote Memory Reference (RMR) complexity for both cache coherent and distributed shared memory machines; and (2) is the first that can be accessed by arbitrarily many dynamically allocated processes and with arbitrarily many session names. Neither of the existing GME algorithms satisfies either of these two important properties. In addition, our algorithm has constant space complexity per process and satisfies the two strong fairness properties, first-come-first-served and first-in-first-enabled. Our algorithm uses an atomic instruction set supported by most modern processor architectures, namely: read, write, fetch-and-store and compare-and-swap

Group mutual exclusion in linear time and space

We present two algorithms for the Group Mutual Exclusion (GME) Problem that satisfy the properties of Mutual Exclusion, Starvation Freedom, Bounded Exit, Concurrent Entry and First Come First Served. Both our algorithms use only simple read and write instructions, have O (N) Shared Space complexity and O (N) Remote Memory Reference (RMR) complexity in the Cache Coherency (CC) model. Our �rst algorithm is developed by generalizing the well-known Lamport’s Bakery Algorithm for the classical mutual exclusion problem, while preserving its simplicity and elegance. However, it uses unbounded shared registers. Our second algorithm uses only bounded registers and is developed by generalizing Taubenfeld’s Black and White Bakery Algorithm to solve the classical mutual exclusion problem using only bounded shared registers. We show that contrary to common perception our algorithms are the �rst to achieve these properties with this combination of complexities.ECU Open Access Publishing Support Fun

A framework to study the performance of the group mutual exclusion algorithms

Group mutual exclusion problem generalizes the classical mutual exclusion problem, a fundamental problem in concurrent programming. It arises in applications involving sharing resources such as memory and data. In group mutual exclusion, a process requests for a “forum”; processes requesting the same forum may access the critical section simultaneously. Several algorithms have been proposed for the group mutual exclusion problem, but very few studies have been conducted to compare the performances of these algorithms by means of execution on actual machines. Besides the studies conducted have been a mere one-on-one comparison. Also, there exists no testing environment that accommodates multiple algorithms and compare their executions. This work aims at testing the performance of group mutual exclusion algorithms extensively by executing multiple such algorithms in a test framework. We propose to build an automated test framework to execute these algorithms, both individually and collectively under various experimental setups and observe their performances graphically using several performance metrics. Our experiments would constitute several collective comparison studies of algorithms along with replicating a few one-on-one comparison experiments from the literature. To use the algorithms into our framework, we intend to translate them from pseudo codes to source codes. The aim is to eventually creating a repository of these source codes such that they could be used for other applications besides our framework

Group Mutual Exclusion in Linear Time and Space

The Group Mutual Exclusion (GME) problem, introduced by Joung, is a natural extension of the classical Mutual Exclusion problem. In the classical Mutual Exclusion problem, two or more processes are not simultaneously allowed to be in their CRITICAL SECTION, a piece of code where a common resource is accessed. In the GME problem, it is necessary to impose mutual exclusion on different groups in processes in accessing a resource, while allowing processes of the same group to share the resource. The Group Mutual Exclusion problem arises in several applications and is the focus of this thesis. We present an algorithm for the GME problem that satisfies the properties of Mutual Exclusion, Starvation Freedom, Bounded Exit, Concurrent Entry and First-Come-First Served. Our algorithm has [theta] (N) shared space complexity and [omicron] (N)RMR (Remote Memory Reference) complexity. Our algorithm is developed by generalizing the well-known Lamport's Bakery Algorithm for the classical mutual exclusion problem, while preserving its simplicity and elegance. Just like Lamport's Bakery Algorithm, our algorithm has the disadvantage that the token numbers can grow in an unbunded manner. When all shared variables are required to be of bounded size, Hadzilacos presented an algorithm, whose shared space complexity is [theta] (N²) and whose RMR complexity is claimed to be [omicron] (N). Hadzilacos posed as an open problem, the development of a linear time and space algorithm that uses only bounded shared variables and only simple read and write instructions. As a solution to the open problem, Jayanti et al. presented a space efficient adaptation of the above algorithm that uses only [theta] (N) shared space and inherited the claim that the RMR complexity is [omicron] (N) We show that both of these algorithms are of RMR complexity [omega] (N²) and thus demonstrate that both claims are erroneous. So, the open problem posed by Hadzilacos is still open.Open Access FundingM.S