critical-section problem

Karl Popper (1902-1994) is one of the most eminent philosophers of the 20th century which reconfigured the scientific method through the creation of the project (critical spirit) as an alternative to the model of certainty and traditional verification, as contributions from the philosophy of science tendencies Doughanism in Both Natural and Human Sciences, We Aim, Through this philosophical approval Attempt to establish a new Critical Epistemology, The Principle of Open, Critical, Monetary, To Achieve the Maximum Degree of Accuracy and Scientific Certainsy to Understand the
Human Experience in the Field of Multiple Cultural Perceptions, and Social Systems Through the Draft Critical Objectivity in Front of the Bets and Challenges The humanities, and social sciences to enhance Critical Dynamics and overcome the risks of current ideological stagnation, that forces us to present the following problem: How did Karl Popper establish an open rationality as an alternative to false neutrality? What is the truth of human? The answer to this problem confirms that man has always occupied the centrality of the epistemic field of humanities, and social and socially based on the controversy of the transcendent and realistic idealism within the dualism of being and nature, but with the end of the nineteenth century the human being occupied the field of experimental studies towards objective knowledge through the establishment of the ego’s ego through self-experience, which forced humanities and social sciences from the birth of modern science to this day to this day to this day to this day The imperative to overcome all classical curricula and studies based on ancient Greek perceptions, and the intellectual and systematic transition towards the scientific situation, to achieve its presence in the cognitive field through an attempt to establish an accurate objective independence by adopting the experimental approach like other modern science as "the" path leading to revealing the truth in science by a group of general rules that dominate the progress of the mind, and determines its operations until it reaches a known result".

The purpose of this research is not only to move beyond traditional concepts of knowledge but also to emphasize the significance of Kant’s critical philosophy. This philosophical approach constructs knowledge on critical foundations and can significantly contribute to the development of human understanding. The study concludes that the human mind has clear boundaries. If these boundaries are exceeded, both certainty and truth may be compromised. If we examine closely many of the great discoveries made by humanity’s most brilliant minds in the fields of science, philosophy, and art, we notice something striking. These discoveries often possess simplicity, clarity, or an intuitive quality. At the same time, it is surprising that humanity took so long to uncover such straightforward facts and obvious evidence. One such revelation may be the critique of reason itself. We might wonder how humanity spent centuries before any philosopher proposed that the human mind should be examined and tested. Why did no one argue earlier for the need to assess the mind’s ability to know before using it as a tool to seek truth? This was precisely the work undertaken by Immanuel Kant (1724-1804). He critically examined the "human mind" before relying on it to explore theological, metaphysical, and hidden truths. His “critical philosophy” began as a systematic effort to define the exact boundaries within which the mind can be reliably used as a source of knowledge. According to Zakaria Ibrahim (1972), critical philosophy is, at its core, a methodical attempt to establish the legitimate limits of the mind’s role in the pursuit of knowledge.

The Multiprocessor Bandwidth Inheritance (M-BWI) protocol is an extension of the Bandwidth Inheritance (BWI) protocol to symmetric multiprocessor systems. Similarly to Priority Inheritance, M-BWI lets a task that has locked a resource execute in the resource reservations of the blocked tasks, thus reducing their blocking time. The protocol is particularly suitable for open systems where different kinds of tasks dynamically arrive and leave, because it guarantees temporal isolation among independent subsets of tasks without requiring any information on their temporal parameters. Additionally, if the temporal parameters of the interacting tasks are known, it is possible to compute an upper bound to the interference suffered by a task due to other interacting tasks. Thus, it is possible to guarantee a subset of interacting hard real-time tasks. Finally, the M-BWI protocol is neutral to the underlying scheduling policy, because it can be implemented both in global, clustered and partitioned scheduling. After introducing the M-BWI protocol, in this paper we formally prove its isolation properties, and propose a schedulability analysis for hard real-time tasks. Then, we describe our implementation of the protocol for the LIT M U S RT real-time testbed, and measure its overhead. Finally, we compare M-BWI against FMLP, another protocol for resource sharing in multiprocessor systems, introducing a schedulability analysis for M-BWI that proves to be less pessimistic than existing analysis techniques for FMLP.

In this paper we present an architecture design for supporting real time computing on Linux. This architecture focuses on improving the usability of real time capabilities for applications by providing a unified Application Programming Interface. Applications can therefore use it without having to know exactly what the underlying scheduling algorithm is. Still, the real-time computing capabilities of the platform may be exploited to the maximum extent. The main aim of the paper is to gather feedback from the community about the design and directions for development. * The research leading to these results has received funding from the European Community's Seventh Framework Programme FP7 under grant agreement n. 214777 "IRMOS-Interactive Realtime Multimedia Applications on Service Oriented Infrastructures" and n. 248465 "S(o)OS--Service-oriented Operating Systems".

Abstract| W e present a self-stabilizing token passing algorithm for a tree network. The algorithm is based on the 4-state mutual exclusion algorithm of Dijkstra 5] and works under the distributed daemon model of execution. Keywords|Distributed algorithms, fault-tolerance, mutual exclusion, self-stabilization, token passing.

Invalidation-based cache coherence protocols have been extensively studied in the context of large-scale shared-memory multiprocessors. Under a relaxed memory consistency model, most of the write latency can be hidden whereas cache misses still incur a severe performance problem. By contrast, update-based protocols have a potential to reduce both write and read penalties under relaxed memory consistency models because coherence misses can be completely eliminated. The purpose of this paper is to compare update-and invalidation-based protocols for their ability to reduce or hide memory access latencies and for their ease of implementation under relaxed memory consistency models. Based on a detailed simulation study, we find that write-update protocols augmented with simple competitive mechanisms -we call such protocols competitive-update protocols -can hide all the write latency and cut the read penalty by as much as 46% at the cost of some increase in the memory traffic. However, as compared to write-invalidate, update-based protocols require more aggressive memory consistency models and more local buffering in the second-level cache to be effective. In addition, their increased number of global writes may cause increased synchronization overhead in applications with high contention for critical sections.

In Software Defined Radios FPGAs can be used as both an interconnect layer and a general-purpose computational fabric implementing hardware acceleration units. Typical implementations of software defined radio (SDR) modems include a general purpose processor (GPP), digital signal processor (DSP) and field programmable gate array (FPGA). The FPGA fabric can be used to offload either the GPP or DSP (or both). Hardware acceleration units in conjunction with small embedded microprocessors can be used as coprocessors to the GPP or DSP, accelerating critical sections of either DSP or GPP code in hardware. Moreover, with general purpose routing resources available in the FPGA, hardware acceleration units can run in parallel to further enhance the total computational output of the system. The algorithms and systems can be modeled in high-level languages or tools such as C or Matlab/Simulink and easily ported to hardware acceleration units running on the FPGA. The creation and use of hardwar...

The amount of biosequence data being produced each year is growing exponentially. Extracting useful information from this massive amount of data efficiently is becoming an increasingly difficult task. There are many available software tools that molecular biologists use for comparing genomic data. This paper focuses on accelerating the most widely used such tool, BLAST. Mercury BLAST takes a streaming approach to the BLAST computation by off loading the performance-critical sections to specialized hardware. This hardware is then used in combination with the processor of the host system to deliver BLAST results in a fraction of the time of the general-purpose processor alone. This paper presents the design of the ungapped extension stage of Mercury BLAST. The architecture of the ungapped extension stage is described along with the context of this stage within the Mercury BLAST system. The design is compact and runs at 100 MHz on available FPGAs, making it an effective and powerful component for accelerating biosequence comparisons. The performance of this stage is 25× that of the standard software distribution, yielding close to 50× performance improvement on the complete BLAST application. The sensitivity is essentially equivalent to that of the standard distribution.

In this paper, we investigate distributed mutual exclusion algorithms and delineate the features of a new distributed mutual exclusion algorithm. The basis of the algorithm is the logical ring structure employed in token-based mutual exclusion algorithms. Specifically, there exists dynamic properties of the logical ring that, given certain restrictions regarding message traffic flow, passively give useful information about the location

This paper presents a simple mutual exclusion algorithm for ad hoc mobile networks. Our algorithm does not use the token circulation technique. A station which requests a Critical Section (CS) competes in order to be alone to use the unique channel dedicated to this CS. To reach this goal, we derive a Markov process which guarantees that each station will enter the C^. More precisely, we show that, in presence of collision detection, n/ln2 broadcast rounds are necessary in the average case to satisfy n (n unknown) stations wishing to enter the same CS.

This paper presents a simple mutual exclusion algorithm for ad hoc mobile networks. Our algorithm does not use the token circulation technique. A station which requests a Critical Section (CS) competes in order to be alone to use the unique channel dedicated to this CS. To reach this goal, we derive a Markov process which guarantees that each station will enter the C^. More precisely, we show that, in presence of collision detection, n/ln2 broadcast rounds are necessary in the average case to satisfy n (n unknown) stations wishing to enter the same CS.

In a distributed system, process synchronization is an important agenda. One of the major duties for process synchronization is mutual exclusion. In new algorithm, opposite the past algorithms fairness happens. This paper presents a new approach of the race models involving distributed mutual exclusion. Further, concrete applications of these models did not involve variability in the accumulator size or were based on a specific distribution. We show that the distributions of time stamp, time action and the other effective parameters predicted by the neural network competitive models can be solved analytically this problem that be happens in the critical sections. The model can be manipulated and simulated to predict the effects of reward on Hamming and Hopfield's models curves and speed-accuracy decomposition. In other hand, the major contribution of this paper is the implementation of a learning rule that enables networks based on a race model to learn stimulus-response associations. The model described here can be seen as a reduction of information system and is compatible with a priority learning system. Also, we will consider the non-linear behavior of the competitive models and as a result use this property in distributed systems. Finally, it is possible to use the neural networks as a distributed system pattern, to optimization of fault tolerance, reliability and accessibility related to mutual exclusion and critical section. Thus in the new approach fault tolerance will ascend and centralize and distributed algorithms can use this and based algorithm will be more reliable.

Resource allocation is the problem that a process may enter a critical section CS of its code only when its resource requirements are not in conflict with those of other processes in their critical sections. For each execution of CS, these requirements are given anew. In the resource requirements, levels can be distinguished, such as e.g. read access or write access. We allow infinitely many processes that communicate by reliable asynchronous messages and have finite memory. A simple starvation-free solution is presented. Processes only wait for one another when they have conflicting resource requirements. The correctness of the solution is argued with invariants and temporal logic. It has been verified with the proof assistant PVS.

A mathematical algorithm is developed and presented for use in conjunction with the Imposed Rotation Method as reformulated by Kaneko as a (n * 2n) linear complementarity problem. The inelastic tri-linear moment rotation law which is modelled to reflect behaviour at critical sections is adjusted during the incremental analysis in order to adhere to the non-holonomic behaviour of reinforced concrete when stress unloading occurs. The developed algorithm also incorporates the two relevant failure criteria, namely local failure and failure by the formation of a collapse mechanism. A typical reinforced concrete frame is analyzed under different load combinations to show the features of the developed algorithm.

The MCS lock was the first mutual exclusion lock to support an arbitrary number of processes with unknown identities such that each process can acquire and release the lock in a constant number of RMRs on both Cache-Coherent and Distributed Shared Memory multiprocessors. The MCS algorithm, however, has a shortcoming: its Exit section is not bounded. The algorithm also requires hardware support for more than one special instruction, namely, Fetch&Store and Compare&Swap. Many MCS-style algorithms were subsequently designed to overcome these shortcomings, but to the best of our knowledge they either lack some desirable property of the MCS lock or introduce a new shortcoming. In this paper we present a new MCS-style algorithm that has all of the desirable properties and no ostensible shortcoming. We also provide a rigorous, invariant-based proof of correctness. To realize a bounded Exit section, all prior MCS-style algorithms use either the "node-switching" or the "node-toggling" strategy. Our work unifies these two strategies: we present a single algorithm which, when appropriately instantiated, yields both a nodeswitching and a node-toggling algorithm. Moreover, the two algorithms so derived are the simplest in their respective classes among all known MCS-style algorithms. • Theory of computation → Concurrent algorithms.

The group mutual exclusion (GME) problem is an interesting generalization of the mutual exclusion problem. Several solutions of the GME problem have been proposed for message passing distributed systems. In this paper we present a new Distributed Group Mutual Exclusion (DGME) based on Clients/Servers model, and uses a dynamic data structure. Several processes (Clients) can access simultaneously to a same opened session (Server). The algorithm ensures that, at any time, at most one session is opened, and any requested session will be opened in a finite time. The number of messages is between 0 and m, where m is the number of session in the network. In the average case, O(Log(m)) messages are necessary to open a session. The maximum concurrency is n, where n is the number of processes in the network.

Mutual exclusion is one of the mechanisms that can be used to solve concurrency problems in the operating system. In the operating system, there are resources that cannot be shared at the same time, such as printers. These kinds of resources are called critical resources. Programs that use critical resources are called entering critical regions/sections. Programmers cannot rely on the operating system to understand and enforce these limits. The mutual exclusion settlement process was submitted by several experts. One of them is Lamport with a method known as Lamport's Bakery Algorithm. The work process of Lamport's Bakery Algorithm starts from the buyer entering the store and receiving the sequence number. If there is a waiter who is idle (not being / will serve other buyers), then the buyer directly asks for service from the waiter. If not, then the buyer sits in the buyer's waiting area and waits until his turn. Shoppers who have finished being served out of the store ...

This paper considers the use of lock-free shared objects within hard r eal-time systems. As the name suggests, lock-free shared objects are distinguished by the fact that they are not locked. As such, they do not give rise to priority inversions, a key advantage over conventional, lock-based object-sharing approaches. Despite this advantage, it is not immediately apparent that lock-free shared objects can be employed if tasks must adhere to strict timing constraints. In particular, lock-free object implementations permit concurrent operations to interfere with each other, and repeated interferences can cause a given operation to take an arbitrarily long time to complete. The main contribution of this paper is to show that such interferences can be b ounded by judicious scheduling. This work pertains to periodic, hard r eal-time tasks that share l o ck-free objects on a uniprocessor. In the rst part of the paper, scheduling conditions are derived for such tasks, for both static and dynamic priority schemes. Based on these conditions, it is formally shown that lock-free object-sharing approaches can be expected to incur much less overhead than approaches based on wait-free objects or lock-based schemes. In the last part of the paper, this conclusion is validated experimentally through work involving a realtime desktop videoconferencing system.

The distributed k-mutual exclusion problem or, simply the k-mutex problem, is the problem of allowing at most k processes to access their critical sections simultaneously. This might be the consequence where k identical copies of a resource are made available in the distributed system or that the resource by its nature can be accessed by at most k processes simultaneously. When a process enters it critical section such that there are l < k processes in their critical sections, there is no interference of the mutual exclusion condition. In this paper, we present an algorithm for the k-mutex problem. The algorithm is token based and k tokens are used. A node may enter the critical section only if it possesses a token. The algorithm has a worst case message complexity of Oð ffiffiffi n p Þ. Under heavy load the message requirement approaches 2 per critical section entry. The algorithm has been modified to enable fault tolerant capabilities. We have discussed node failure, message loss and link failure.

In this paper a distributed algorithm is proposed that realises mutual exclusion among n nodes in a computer network. There is no common or global memory shared by the nodes and there is no global controller. The nodes of the network communicate among themselves by exchanging messages only. The proposed algorithm is based on queue migration and achieves a message complexity of O(√n) per mutual exclusion invocation. Under heavy load, the number of required messages approaches 2 per mutual exclusion.

In this paper a distributed algorithm is proposed that realises mutual exclusion among n nodes in a computer network. There is no common or global memory shared by the nodes and there is no global controller. The nodes of the network communicate among themselves by exchanging messages only. The proposed algorithm is based on queue migration and achieves a message complexity of O(√n) per mutual exclusion invocation. Under heavy load, the number of required messages approaches 2 per mutual exclusion.

Fire tests were performed to investigate the mechanics and capacity of steel beam-columns that develop a thermal gradient through their depth when exposed to fire. Wide-flanged specimens were loaded axially and tested vertically in a furnace recently commissioned at Michigan State University. The placement of insulation simulated a realistic three-sided heating scenario such as that experienced by a column on the perimeter of a building frame. Specimens were tested with several combinations of load level, fire scenario, and direction of the thermal gradient (which dictates the direction of bending). The different combinations of tested parameters had a significant influence on the fire response of these columns, which all failed by full section yielding due to a combination of axial load (P) and moment (M). These columns developed bending moments in response to through-depth thermal gradients as well as a moment reversal due to a shift in the section's center of stiffness. The plastic resistance to combinations of axial load and moment was also affected by the thermal gradients such that the critical section, located in the hottest region along the column length, was where moment was the smallest (not the largest, as would be intuitively expected). The experiments and computer models showed good agreement with the predicted demands (i.e. bending moment reversal) and capacity (i.e. changes in the plastic P-M capacity).

In distributed shared memory multiprocessors, remote memory accesses generate processor-tomemory traffic which may result in a bottleneck. It is therefore important to design algorithms that minimize the number of remote memory accesses. We establish a lower bound of 3 on remote access time complexity for mutual exclusion algorithms in a model where processes communicate by means of a general read-modify-write primitive. Since a general read-modify-write primitive is a generalization of all atomic primitives that access at most one shared variable, our lower bound holds for any set of such primitives. Furthermore, this lower bound is tight because it matches the upper bound of Huang's algorithm proposed in 1999.

Transactional Memory (TM) is a promising new technology that makes it possible to ease writing multi-threaded applications. Many different TM implementations exist, unfortunately most of those TM systems are currently evaluated by using workloads that are (1) tightly coupled to the interface of a particular TM implementation, (2) are small and lack to capture the common concurrency problems that exist in real multi-threaded applications and also (3) fail to evaluate the overall behavior of the Transactional Memory considering the complete software stack.

This paper considers the use of lock-free shared objects within hard r eal-time systems. As the name suggests, lock-free shared objects are distinguished by the fact that they are not locked. As such, they do not give rise to priority inversions, a key advantage over conventional, lock-based object-sharing approaches. Despite this advantage, it is not immediately apparent that lock-free shared objects can be employed if tasks must adhere to strict timing constraints. In particular, lock-free object implementations permit concurrent operations to interfere with each other, and repeated interferences can cause a given operation to take an arbitrarily long time to complete. The main contribution of this paper is to show that such interferences can be b ounded by judicious scheduling. This work pertains to periodic, hard r eal-time tasks that share l o ck-free objects on a uniprocessor. In the rst part of the paper, scheduling conditions are derived for such tasks, for both static and dynamic priority schemes. Based on these conditions, it is formally shown that lock-free object-sharing approaches can be expected to incur much less overhead than approaches based on wait-free objects or lock-based schemes. In the last part of the paper, this conclusion is validated experimentally through work involving a realtime desktop videoconferencing system.

1. The new paradigm shift widens the definition of life to bio-environmental systems, while the environment-health relationship remains exclusively linked to (i) infections, (ii) pollution, (iii) geo-climatic alterations: few extend the relation to the landscape units. So, Medicine should change from sick care to health care; Ecology presents many limits and was upgraded by Landscape Bionomics (LB).
2. Following LB and the capacity of vegetation to control energy, matter, and information, we discovered a systemic function able to evaluate the flux of energy available to maintain the order reached by a complex phytocoenosis: BTC (biological territorial capacity of vegetation). It is based on (a) the concept of resistance stability, (b) the type of vegetation community, (c) its metabolic data (B, NP, GP R), (d) their metabolic relations R/GP (respiration/gross production), (e) their order relations R/B = dS/S (antithermic maintenance). We calculated two coefficients: (ai) measures the degree of the relative metabolic capacity of the phytocoenosis of the Biosphere, (bi) measures the degree of the relative antithermic maintenance of the same vegetation communities. The allostatic capacity of a bionomic system is proportional to its respiration: ai and bi related to respiration, give the measure of BTC. 
3. The Landscape Bionomic Survey of Vegetation (LaBiSV) has been proposed. Main characters: (a) reference to the ecocoenotope and ecotissue as landscape structural entities and to BTC as integrative function; (b) development model “time-BTC” for different types of vegetation based on a logarithmic and exponential functions; The HH/BTC bionomic model allows the emergence of a curve of normality. The ratio with a surveyed values below that curve (BTCsurv/BTCnorm) leads to BF values: Bionomic Functionality. The information content of a landscape unit is also evaluated.
4. We report some case study leading to the emergence of pathologic factors: (a) ecological services related to human habitats, (b) increase of MR (mortality rate) with the BF alteration, (c) decrease of BTC in EU countries correlated with the increase of cancer onset.
5. At least 8-10 types of processes try to explain health alteration due to environmental degradation of landscape units, independently from pollution. Here we present a summary on (a) ethological alarm due to environmental stress, (b) information disturbances by altered BTC landscapes, (c) therapeutical effects of high BTC forests, (d) a logical flow-chart summarizing etiological processes, (e) the Body internal and external life systems.
6. To study the environment/health relationships, the BTC function is essential.

Distributed mutual exclusion is a fundamental problem of distributed systems that coordinates the access to critical shared resources. It concerns with how the various distributed processes access to the shared resources in a mutually exclusive manner. This paper presents fully distributed improved token based mutual exclusion algorithm for distributed system. In this algorithm, a process which has owing token, could enter to its critical section. The processes communicate to each other in an asynchronous message passing manner. We assume the distributed processes are organized in a wraparound two dimensional array. Also, the communication graph of the network is supposed to be a complete graph. The proposed algorithm uses three types of messages, namely ReqMsg, InfoMsg and RelMsg. Beside token-holding node, there are some nodes, we call them informed-nodes, which can know token-holding node and transmit request message to it directly. The number of messages, which are exchanged per each critical section entrance, is a key parameter to avoid posing additional overhead to the distributed system. In this paper, we obtain to 3√ − 1 messages per critical section access where N is the number of nodes in the system. The proposed algorithm outperforms other token based algorithms whilst fairness is kept and the proposed algorithm is starvation free.

Mutual exclusion is a fundamental distributed coordination problem. Shared-memory mutual exclusion research focuses on local-spin algorithms and uses the remote memory references (RMRs) metric. To ensure the correctness of concurrent algorithms in general, and mutual exclusion algorithms in particular, it is often required to prohibit certain re-orderings of memory instructions that may compromise correctness, by inserting memory fence (a.k.a. memory barrier) instructions. Memory fences incur non-negligible overhead and may significantly increase time complexity. A mutual exclusion algorithm is adaptive to total contention (or simply adaptive), if the time complexity of every passage (an entry to the critical section and the corresponding exit) is a function of total contention, that is, the number of processes, k, that participate in the execution in which that passage is performed. We say that an algorithm A is f-adaptive (and that f is an adaptivity function of A), if the time complexity of every passage in A is O f (k). Adaptive implementations are desirable when contention is much smaller than the total number of processes, n, sharing the implementation. Recent work [5] presented the first read/write mutual exclusion algorithm with asymptotically optimal complexity under both the RMRs and fences metrics: each passage through the critical section incurs O(log n) RMRs and a constant number of fences. The algorithm works in the popular Total Store Ordering (TSO) model. The algorithm of [5] is non-adaptive, however, and they posed the question of whether there exists an adaptive mutual exclusion algorithm with the same complexities. We provide a negative answer to this question, thus capturing an inherent cost of adaptivity. In fact, we prove a stronger result: adaptive read/write mutual exclusion algo-* Partially supported by the Israel Science Foundation (grants 1227/10, 1749/14) and by the Lynne and William Frankel Center for Computing Science at Ben-Gurion University.

As vehicular networking has recently been developed and commercialized, vehicular cloud computing has received much attention in various research areas, such as intelligent transportation systems and vehicular ad hoc networks. An efficient intersection traffic control using vehicular cloud computing is one of the key research topics in intelligent transportation systems. To efficiently deal with intersection traffic control via vehicle-to-vehicle communications, we design a distributed mutual exclusion algorithm that does not rely on broadcast, which introduces communication overheads; instead, our algorithm use point-to-point messages sent between the vehicles to keep network traffic load lower. In our algorithmic design, to pass an intersection, the lead vehicle on a lane must get permissions from a subset of other vehicles and its following vehicles on the same lane can follow the lead vehicle without permissions unlike the previous research. To evaluate the performance of our distributed mutual exclusion

The lock set method and the partial order method are two main approaches to guarantee that dynamic data race prediction remains efficient. There are many variations of these ideas. Common to all of them is the assumption that the events in a critical section belong to the same thread. We have evidence that critical sections in the wild do extend across thread boundaries even if the surrounding acquire and release events occur in the same thread. We introduce the novel concept of a cross-thread critical section to capture such situations, offer a theoretical comprehensive framework, and study their impact on state-of-the-art data race analyses. For the sound partial order relation WCP we can show that the soundness claim also applies to cross-thread critical sections. For DCtp the occurrence of cross-thread critical sections invalidates the soundness claim. For complete partial order relations such as WDP and PWR, cross-thread critical sections help to eliminate more false positives. The same (positive) impact applies to the lock set construction. Our experimental evaluation confirms that cross-thread critical sections arise in practice. For the complete relation PWR, we are able to reduce the number of false positives. The performance overhead incurred by tracking cross-thread critical sections slows down the analysis by 10%-20%, on average.

In this paper we present a solution to the 'Latest Gossip Problem' for a shared memory distributed system. The Latest Gossip Problem is essentially one of bounded timestamping in which processes must locally keep track of the 'latest' information, direct or indirect, about all other processes. A solution to the Latest Gossip Problem is fundamental to the understanding of information flow in a distributed computation, and has applications to problems such as global state detection and mutual exclusion. Our solution is along the lines of that for message passing systems in [6], and for synchronously communicating systems [8]. Our algorithm uses a modified version of the consume and update protocols of Dwork and Waarts [3], where these were introduced to construct a 'Bounded Concurrent Timestamping System (BCTS)'. As applications of our Gossip Protocol, we also indicate another construction of a BCTS and a solution to the global state detection problem, which, we believe, are improvements over older solutions.

In this paper we present a solution to the 'Latest Gossip Problem' for a shared memory distributed system. The Latest Gossip Problem is essentially one of bounded timestamping in which processes must locally keep track of the 'latest' information, direct or indirect, about all other processes. A solution to the Latest Gossip Problem is fundamental to the understanding of information flow in a distributed computation, and has applications to problems such as global state detection and mutual exclusion. Our solution is along the lines of that for message passing systems in [6], and for synchronously communicating systems [8]. Our algorithm uses a modified version of the consume and update protocols of Dwork and Waarts [3], where these were introduced to construct a 'Bounded Concurrent Timestamping System (BCTS)'. As applications of our Gossip Protocol, we also indicate another construction of a BCTS and a solution to the global state detection problem, which, we believe, are improvements over older solutions.

Expert systems for decision support have recently been successfully introduced in road transport management. These systems include knowledge on tra c problem detection and alleviation. The paper describes experiments in automated acquisition of knowledge on tra c problem detection. The task is to detect road sections where a problem has occured (critical sections) from sensor data. It is necessary to use inductive logic programming (ILP) for this purpose as relational background knowledge on the road network is essential. In this paper, we apply three state-of-the art ILP systems to learn how to detect tra c problems and compare their performance to the performance of a propositional learning system on the same problem.

This paper presents a fault-tolerant algorithm ensuring multiple resources sharing in mobile ad hoc networks (MANETs) that is able to handle the known K-mutual exclusion problem in such mobile environments. The proposed algorithm relies on a token-based strategy, and requires information about resources and their use to be carried in routing protocol control messages. This way, our solution avoids any additional exchange of messages. Furthermore, experimental results show that it offers a fast response time. Moreover, we introduce a dual-layer fault-tolerance mechanism that tolerates the faults of several sites at the same time without affecting the well functioning of the system. Simulation results also evidence the high efficiency of our proposal, which achieves reduced overhead and response delay even in the presence of critical situations where multiple simultaneous faults occur.

This paper presents a fault-tolerant algorithm ensuring multiple resources sharing in mobile ad hoc networks (MANETs) that is able to handle the known K-mutual exclusion problem in such mobile environments. The proposed algorithm relies on a token-based strategy, and requires information about resources and their use to be carried in routing protocol control messages. This way, our solution avoids any additional exchange of messages. Furthermore, experimental results show that it offers a fast response time. Moreover, we introduce a dual-layer fault-tolerance mechanism that tolerates the faults of several sites at the same time without affecting the well functioning of the system. Simulation results also evidence the high efficiency of our proposal, which achieves reduced overhead and response delay even in the presence of critical situations where multiple simultaneous faults occur.

To fully exploit the scaling performance in Chip Multiprocessors, applications must be divided into semi-independent processes that can run concurrently on multiple cores within a system. One major class of such applications, shared-memory, multi-threaded applications, requires programmers insert thread synchronization primitives (i.e. locks, barriers, and condition variables) in their critical sections to synchronize data access between processes. For this class of applications, scaling performance requires balanced per-thread workloads with little time spent in critical sections. In practice, however, threads often waste significant time waiting to acquire locks/barriers in their critical sections, leading to thread imbalance and poor performance scaling. Moreover, critical sections often stall data prefetchers that mitigate the effects of long critical section stalls by ensuring data is preloaded in the core caches when the critical section is complete. In this paper we examine a pure hardware technique to enable safe data prefetching beyond synchronization points in CMPs. We show that successful prefetching beyond synchronization points requires overcoming two significant challenges in existing prefetching techniques. First, we find that typical data prefetchers are designed to trigger prefetches based on current misses. This approach this works well for traditional, continuously executing, single-threaded applications. However, when a thread stalls on a synchronization point, it typically does not produce any new memory references to trigger a prefetcher. Second, even in the event that a prefetch were to be correctly directed to read beyond a synchronization point, it will likely prefetch shared data from another core before this data has been written. While this prefetch would be considered "accurate" it is highly undesirable, because such a prefetch would lead to three extra "ping-pong" movements back and forth between private caches in the producing and consuming cores, incurring more latency and energy overhead than without prefetching. We develop a new data prefetcher, Multi-Thread B-Fetch (MTB-Fetch), built as an extension to a previous single-threaded data prefetcher. MTB-Fetch addresses both issues in prefetching for shared memory multi-threaded workloads. MTB-Fetch achieves a speedup of 9.3% for multi-threaded applications with little additional hardware.

In this paper we define the Weak Mutual Exclusion (WME) problem. Analogously to classical Distributed Mutual Exclusion (DME), WME serializes the accesses to a shared resource. Differently from DME, however, the WME abstraction regulates the access to a replicated shared resource, whose copies are locally maintained by every participating process. Also, in WME, processes suspected to have crashed are possibly ejected from the critical section We prove that, unlike DME, WME is solvable in a partially synchronous model, i.e. a system where the bounds on communication latency and on relative process speeds are not known in advance, or are known but only hold after an unknown time. Finally we demonstrate that ♦P is the weakest failure detector for solving WME, and present an algorithm that solves WME using ♦P with a majority of correct processes.

In this paper, we design and analyze a mutual exclusion algorithm, based on the Token and Failure detector, in asynchronous distributed systems. A Failure Detector is an independent module that detects and reports crashes of other processes. There are some of advantages in rewriting the Token-based ME algorithm using a Failure Detector. We show that the Token-based ME algorithm, when using Failure Detector, is more effectively implemented than the classic Token-based ME algorithm for synchronous distributed systems.

A fuzzy neural network was implemented using a multithreading approach for detection of atrial fibrillation, bigeminy, and normal sinus rhythm in the MIT-BIH Arrhythmia Database. The feedforward multilayer perceptron neural network produces fuziy outputs due to a modification of the learning algorithm that changes the crisp target labels for fuzzy target labels. The input data to the neural network consisted of nine inputs: Seven contiguous RR intervals, their average and their standard deviation. The trained f u z y neural network was implemented using concurrent thread synchronization with critical sections for mutual exclusion and process synchronization with semaphores. Concurrent process synchronisation is slower but allows data sharing among dflerent process. Sensitivity and positive predictivity rates above 90 % for atrial fibrillation episode and duration detection were reached in the database. cardiac chambers. During this process, the atrial mass may react to more than 500 impulses per minute, completing each depolarisation-repolarisation. On direct visualisation, the atrial chambers are found to have a continuous shimmering action rather than intermittent forceful contractions. Atrial fibrillation in the ECG is represented by continuous, irregular waves on the baseline. In AF, the ventricles appears to respond randomly to the extremely rapid assault of f waves. In fact, irregularity of the ventricular rate is a characteristic of AF. The QRS retain their usual configuration and the most common ventricular rate response is about 150 to 180 per minute, but this is variable[ 11. Another common alteration of the heart rhythm are premature ventricular contractions (PVC). PVCs can appear in groups in which case, the term bigeminy (B) or trigeminy is applied depending on the number of PVCs on each group. Long episodes of PVCs can be a warning of incoming severe arrhythmia.

Our work presents a self-stabilizing solution to the '-exclusion problem. This problem is a well-known generalization of the mutual-exclusion problem in which up to ', but never more than ', processes are allowed simultaneously in their critical sections. Self-stabilization means that even when transient failures occur and some processes crash, the system ÿnally resumes its regular and correct behavior. The model of communication assumed here is that of shared memory, in which processes use single-writer multiple-reader regular registers.

Composite such as Glass Fibre Reinforced Polymer (GFRP) is increasingly used as insulation in many industrial applications such as the steel pipelines in the oil and gas industry. Due to ageing and cyclic operation, many hidden defects exist under insulation, such as corrosion and delamination. If these defects are not promptly detected and restored, the growth of defects causes a catastrophic loss. Therefore, an effective inspection technique using non-destructive testing (NDT) to detect the underneath defect is required. The ability of microwave signals to penetrate and interact with the inner structure within composites makes them a promising candidate for composite inspection. In the case of GFRP, the random patterns cause permittivity variations that influence the propagation of the microwave signals, which results in a blurred spatial image making the assessment of the material's state difficult. In this research, a novel microwave NDT technique is presented based on k-means unsupervised machine learning for defect detection in composites. At present, the defect evaluation using an unsupervised machine learning-based microwave NDT technique is not reported elsewhere. The unsupervised machine learning is employed to enhance the imaging efficiency and defect detection in GFRP. The technique is based on scanning the composite material with an open-ended rectangular waveguide operating from 18 to 26.5 GHz with 101 frequency points. The influence of the permittivity variations on the reflected coefficients due to the random patterns of GFRP is mitigated by measuring the mean of a set of the adjacent points at each operating frequency point using a small rectangular window. The measured data is converted to the time domain using a fast inverse Fourier transform (IFFT) to provide significant features and increase the signal resolution to 201-time steps. K-means algorithm is utilized to cluster the given features into the defect and defect-free regions in GFRP. The findings presented in this paper demonstrate the benefits of an unsupervised machine learning to detect a defect down to 1 mm, which is a considerable contribution over any existing defect inspection technique in composites. INDEX TERMS Unsupervised machine learning, k-means, microwave NDT, defect detection.

Resource allocation is the problem that a process may enter a critical section CS of its code only when its resource requirements are not in conflict with those of other processes in their critical sections. For each execution of CS, these requirements are given anew. In the resource requirements, levels can be distinguished, such as e.g. read access or write access. We allow infinitely many processes that communicate by reliable asynchronous messages and have finite memory. A simple starvation-free solution is presented. Processes only wait for one another when they have conflicting resource requirements. The correctness of the solution is argued with invariants and temporal logic. It has been verified with the proof assistant PVS.

Quorum-based distributed coordination protocols provide decentralized control of a shared resource in a distributed system. To guarantee mutually exclusive or mutually consistent access to a resource, each processor in a distributed system obtains permission from a quorum of processors before accessing the resource. To ensure that resource requests made by different processors are arbitrated, the quorums of any two processors must intersect. To prevent failed quorum members from blocking access to the resource, or to optimize quorums for improved performance, it is desirable to adapt quorums as the state of the system changes. Adapting quorums on-line, while the quorum-based coordination protocol continues to operate normally, allows the resource to be accessed with minimum delay. Unless changes to the quorums of different processors are globally coordinated, on-line quorum adaptation can lead to violation of the quorum intersection property essential for correct coordination. In this research, a fault-tolerant, decentralized, and efficient solution to on-line quorum adaptation is given. The solution allows a changing quorum assignment that can consist of any preferred set of intersecting quorums, allowing any desired quorum adaptations that remove failed processors or optimize performance. A decentralized system model is assumed that allows processors to communicate only via unordered point-to-point messages. The synchronization that is necessary and sufficient to solve on-line quorum adaptation in the given system model is derived. Lower bounds are derived on the communication cost of a solution to on-line quorum adaptation. A fully distributed, fault-tolerant algorithm called QADAPT is given that solves the on-line quorum adaptation problem. The algorithm is shown to be correct and to require minimal message passing overhead. Experimental on-line quorum adaptation results using an implementation of QADAPT are reported. iv v Acknowledgments Doing research challenges one to grow in many capacities, whatever the particular focus of one's research. This thesis is dedicated to those who encouraged me to grow as a scientist, an engineer, a professional, and a person of character in the past five years. Because growth of the latter type sustains growth of the former type, I must thank many people who contributed in rather indirect ways to the completion of this thesis work.

Modern network processors deliver a set of methods for implementing critical sections. A number of them rely on specific hardware support and capabilities, while software techniques are still available when hardware support is not flexible enough. Network processors are dedicated to packet processing and their main goal is to achieve the best possible packet processing performance. Therefore, when choosing the implementation method for a particular problem that will be protected by a critical section, the aim must me for the method to influence the overall system performance A wrongly implemented critical section can very easily degrade the level of parallelism and in consequence the performance of the whole system. Sometimes even correctly implemented critical sections can negatively impact the speed of paths that do not need to be protected with a critical section.