Process Synchronization with Readers and Writers Revisited

The readers-writers problem is one of the very well known problems in concurrency theory. It was first introduced by Courtois et.al. in 1971 [1] and requires the synchronization of processes trying to read and write a shared resource. Several readers are allowed to access the resource simultaneously, but a writer must be given exclusive access to that resource. Courtois et.al. gave semaphore-based solutions to what they called the first and second readers-writers problems. Both of their solutions are prone to starvation. The first allows readers to indefinitely lock out writers and the second allows writers to indefinitely lock out readers. This paper presents and proves correct a third semaphore-based solution, which is starvation-free for both reader and writer processes. To the best of our knowledge, this is the first fair semaphore-based solution that at the same time allows several readers to access the resource simultaneously

Let’s Talk About Power: How Teacher Use of Power Shapes Relationships and Learning

Teachers’ use of power in learning environments affects our students’ experiences, our teaching experiences, and the extent to which learning goals are met. The types of conversations we hold or avoid with students send cues regarding how we use power to develop relationships, influence behaviour and entice motivation. Reliance on prosocial forms of power, such as referent, reward, and expert, have a positive impact on outcomes such as learning and motivation, as well as perceived teacher credibility. Overuse of antisocial forms of power that include legitimate and coercive powers negatively affect these same outcomes. In this paper, we share stories from our teaching experiences that highlight how focusing on referent, reward and expert power bases to connect, problem solve, and negotiate challenges with our students has significantly enhanced our teaching practice. We provide resources that can be used by teachers to become aware of and utilize prosocial power strategies in their practice through self-reflection and peer and student feedback

Utilizing Object Compression for Better J2ME Remote Method Invocation in 2.5G Networks

This paper introduces two new Java 2 Platform Micro Edition (J2ME) Remote Method Invocation (RMI) packages. These packages make use of serialized object compression and encryption in order to respectively minimize the transmission time and to establish secure channels. The currently used J2ME RMI package does not provide either of these features. Our packages substantially outperform the existing Java package in the total time needed to compress, transmit, and decompress the object for General Packet Radio Service (GPRS) networks, often called 2.5G networks, even under adverse conditions. The results show that the extra time incurred to compress and decompress serialized objects is small compared to the time required to transmit the object without compression in GPRS networks. Existing RMI code for J2ME can be obliviously used with our new packages

Limitation and capabilities of weak memory consistency systems

Bibliography: p. 158-16

Limitations and Capabilities of Weak Memory Consistency Systems

This dissertation develops and exploits a formalism for specifying memory consistency models. This formalism lays down the foundations for describing memory consistency models at various levels, and develops techniques to prove the equivalence between mod-els defined at different levels. Two levels, called non-operational and operational, are ad-dressed in this dissertation. The non-operational level describes these models in terms of program instructions or procedures, while the operational level describes them in terms of implementation events. Formal techniques are developed to prove the equivalence of rigorous specifications at both levels. This formalism is then exploited to define the memory consistency models of two state-of-the-art multiprocess systems: the SPARC version 8 architecture and the Java Virtual Machine. These models are defined at both operational and non-operational levels. These operational and non-operational descriptions are proved equivalent. The SPARC models provide “reasonably” weak memory consistency models that are capable of avoiding the use of explicit synchronization primitives for certain problems. However, Java provide

Measures to Ensure Assessment Consistency

These are the slides for the presentation/workshop "Measures to Ensure Assessment Consistency in a Large, Multi-Section Course", presented by Jalal Kawash and Robert Collier on May 13, 2014 at the University of Calgary Conference on Postsecondary Learning and Teaching. These slides include a discussion of the challenges associated with unifying course materials across multiple sections, an overview of some basic statistical techniques that can be used to detect many assessment inconsistencies, and a small set of slides used to facilitate the interactive workshop.Ye

Critical Sections and Producer/Consumer Queues in Weak Memory Systems

In machines with weak memory consistency models, the ordering constraints on memory accesses are few. In order to properly program these machines, certain powerful explicit synchronization instructions are additionally provided by their architecture. We show that although a solution to the critical section problem (also referred to as the mutual exclusion problem) is impossible without such powerful synchronization, certain versions of the producer/consumer problem can be solved even in the weakest systems without the need for any such powerful instructions. These instructions are expensive, and avoiding their use is desirable for better performance. 1 Introduction The problem of process coordination has been extensively addressed in the context of sequential consistency. However, modern multiprocessors present a large variety of memory models that are anything but sequentially consistent. Relaxed memory consistency models increase the challenge of solving various coordination proble..