An Efficient File Locking Algorithm for Multi-processor Systems Using Round Robin Delegation Method

The increasing diffusion of shared-memory multi-core machines has given rise to a change in the design of Parallel Discrete Event Simulation (PDES) platforms. In particular, the possibility to share large amounts of memory by many worker threads has lead to a boost in the adoption of non-blocking coordination algorithms, which have been proven to offer higher scalability when compared to their blocking counterparts based on critical sections. In this article we present an innovative non-blocking algorithm for computing Global Virtual Time (GVT)---namely, the current commit horizon---in multi-thread PDES engines to be run on top of multi-core machines. Beyond being non-blocking, our proposal has the advantage of providing a logarithmic (rather than linear) number of per-thread memory operations---read/write operations of values involved in the reduction for computing the GVT value---vs the amount of threads participating in the GVT computation. This allows for keeping low the actual CPU time that is required for determining the new GVT value. We compare our algorithm with a literature solution, still based on the non-blocking approach, but entailing a linear number of memory operations, quantifying the advantages from our proposal especially for very large numbers of threads participating in the GVT computation.

Key-based workload partitioning is a common strategy used in parallel stream processing engines, enabling effective key-value tuple distribution over worker threads in a logical operator. It is likely to generate poor balancing performance when workload variance occurs on the incoming data stream. This paper presents a new key-based workload partitioning framework, with practical algorithms to support dynamic workload assignment for stateful operators. The framework combines hash-based and explicit key-based routing strategies for workload distribution, which specifies the destination worker threads for a handful of keys and assigns the other keys with the hash function. When short-term distribution fluctuations occur to the incoming data stream, the system adaptively updates the routing table containing the chosen keys, in order to rebalance the workload with minimal migration overhead within the stateful operator. We formulate the rebalance operation as an optimization problem, with multiple objectives on minimizing state migration costs, controlling the size of the routing table and breaking workload imbalance among worker threads. Despite of the NP-hardness nature behind the optimization formulation, we carefully investigate and justify the heuristics behind key (re)routing and state migration, to facilitate fast response to workload variance with ignorable cost to the normal processing in the distributed system. Empirical studies on synthetic data and real-world stream applications validate the usefulness of our proposals.

Shared-memory multi-core platforms are changing the nature of Parallel Discrete Event Simulation (PDES) because of the possibility to fully share the workload of events to be processed across threads. In this context, one rising PDES paradigm — referred to as share-everything PDES — is no longer based on the concept of (temporary) biding of simulation objects to worker threads. Rather, each worker threads can — at any time — pick from a fully shared event pool an event to process which can be destined to whatever simulation object. While attention has been posed on the design of concurrent shared pools, allowing non-blocking parallel operations, the scenario where two (or more) threads pick events destined to the same simulation object still lacks adequate synchronization support. In fact, these events are currently sequentialized and processed in a critical section touching the simulation object state, thus leading threads to mutually block each other. In this article we present the design of a share-everything speculative PDES engine that prevents mutual thread blocks because of the access to a same object state. In our design, the non-blocking property is seen as a vertical attribute of the engine (not only of the event pool). This vertical view demands for innovative event-dispatching schemes and, at the same time, innovative interactions with (and management of) the fully-shared event pool, which are features that we embed in our innovative design.

In a shared-memory parallel processing environment there are a number of inherent hardware and software bottlenecks. One of these bottlenecks is the exclusive accesses that are needed to the shared variables within a critical section. The time cost of synchronization of processes which require access to the critical section can be minimized by using optimal scheduling methods. This paper presents a set of pre-run-time optimal scheduling algorithms for accessing the critical sections by the processes which are spawned at FORK operation and are terminated at the associated JOIN operation. >

This paper describes a control structure for the control of parallel processors such that (1) at most one of the processors is engaged in its ‘critical section’ at any instant and (2) if a processor wants to enter a critical section it is eventually allowed to do so. The solution is described using APL programs and flowcharts. It does not assume the existence of ‘indivisible’ operations like ‘TS’ instruction of SYSTEM/360. It is observed that to control ‘N’ processors the number ‘M’ of ‘N-WAY’ switches required is given by: $$M \geqslant 2 + \frac{{Ln{\mathbf{ }}(n - 1)}}{{Ln{\mathbf{ }}2}}$$ KeywordsControl StructureCritical SectionMutual ExclusionParallel ProcessorVersus OperationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The problem studied is similar to the problems found in multiprocessor operating systems. The lockout problem in multiprocessor operating systems is a direct result of multiple processors attempting to process common data structures asynchronously. There are numerous such shared data structures. The models developed are applicable to the study of contention for software and hardware resources in multiprocessor operating systems. The authors introduce an approximate analytical model to evaluate the performance of asynchronous processes found in asynchronous algorithms, including the combined effects of software lockout on critical sections and on job queues, and of shared-memory access conflicts. Because of the strong similarities between the two effects, the same model can be used for both, leading to a uniform and elegant formulation. The models are combined to find the run-time efficiency of asynchronous iterations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A distributed protocol is proposed for the synchronization of real-time tasks that have variable resource requirements. The protocol is simple to implement and is intended for large-scale distributed or parallel systems in which processes communicate by message passing. Critical sections, even when nested, may be executed on any processor. Thus, given an adequate number of processors, the execution of critical sections can be completely distributed. More significantly, since the protocol enables the distributed allocation of critical sections, the benefits of various allocations can be analyzed and the system optimized to provide minimal blocking. This has important application in global optimization techniques for allocating large numbers of hard real-time tasks in multiprocessor systems.

A full-scale 3D thermo-mechanical Finite Element (FE) model was conducted in this research to investigate the effect of open-field thermal loads on the structural response of box-girder bridges. A box-girder bridge with a span of 50 m was analyzed for temperature, radiation and displacement fields using COMSOL Multiphysics. To verify the FE model, a full-scale experimental box-girder segment was constructed and instrumented with temperature, radiation and other sensors. From the experimental records, three days with extreme temperature and radiation measurements were selected. The stresses and displacements are discussed at specific points along the 24 h of the selected days and at specific times along critical sections. The FE analysis showed that the vertical and lateral stress distributions exhibited approximately similar behaviors to their corresponding temperature distributions with minor differences but with reversed sign. The results also showed that the maximum stress was compressive, which was −3.35 MPa in summer −3.83 MPa in winter. On the other hand, the maximum vertical and lateral displacements were 12.5 and 1.2 mm, respectively in summer and 2.7 and 1.9 mm in winter.

The input-queued switch with service class priority is becoming an attractive solution for high-bandwidth ATM switches. In previous related work (see Motoyama, S. et al., IEEE Comm. Letters, vol.3, no.12, p.323-5, 1999), it has been proved that throughput achieves almost 100% for up to 92% of the offered load when random access buffers and a round robin scheduling algorithm are used. However, this is only a theoretical result: the round robin scheduling algorithm is too complex to implement in hardware. We introduce a modification through a scheduling algorithm called iterative longest port first with throughput maximization (iLPFwTM) which is proposed to overcome the complexity of the previous solution regarding its hardware implementation at high speed. A performance analysis is carried out by simulation and the results show a better performance in comparison with the recent ATM input-queued switch with round robin schedulers and service class priority. It means that the ATM input-queued switch with iLPFwTM scheduler and service class priority is proved to be more attractive for high-bandwidth ATM switch implementation than the solution based on a round robin scheduling algorithm.

Behavioral characterization of musth in Asian elephants (Elephas maximus): Defining progressive stages of male sexual behavior in in-situ and ex-situ populations

Short-term Safety Performance Functions by Random Parameters Negative Binomial-Lindley model for Part-time Shoulder Use

Mountainous areas of Switzerland are exposed to complex natural conditions, which combined with climate changes cause a variety of natural hazards. Rockfall is one of these hazards, and the risk associated with it tends to increase in recent years. The roads below the Lopper cliff at the shore of Lake Lucerne lead through one of these endangered areas. The roads are closed for traffic, following a rockfall incident in October 2009. Some rockfall protection galleries at the Lopper, which were built during 1979-1981, are subjected to a structural evaluation to allow for decisions on their further use. The current work covers estimation of the impact load carrying capacity of one of these galleries. The gallery analyzed is a cantilever pre-stressed concrete slab with variable thickness, covered by a cushion layer of soil. The behavior of the gallery is examined using finite element analyses as well as an analytical model based on a System of Multiple Degrees of Freedom (SMDF) method. The evaluation has shown that for the chosen loading case based on trajectory analyses with return periods of 30 years, the load carrying capacity of the gallery is satisfactory. However, for extreme rockfalls with return periods of 100 years, a local (punching) failure as well as a global (bending) failure can happen given that a critical section is hit

A comprehensive investigation on energy consumptions, impacts, and challenges of the food industry

The performance of the multiprocessor system and time-sharing system rely upon CPU scheduling algorithm. Some of the well known efficient CPU scheduling algorithms are Round Robin scheduling (RR), Shortest job first(SJF), Preemptive version of SJF(SRTF), First Come First Serve (FCFS) etc. As of now, the Round Robin scheduling algorithm is considered as the efficient process scheduling algorithm among all the existing CPU scheduling algorithms. However, in RR the shortest one have to wait for a longer time and in SRTF longer process behaves as a suspended process as short tasks keep on executing. This paper proposes a new scheduling process algorithm ESRR (Efficient Shortest Remaining Time Round Robin) that consolidate two of the preemptive version of existing scheduling algorithms namely RR and SRTF. ESRR reduces total waiting time and turn around time in compare to RR and reduces the waiting time of the shorter process and it also provides a longer process to execute faster than SRTF.

To investigate the toxicity of intragastrically administered N, N-dimethylformamide (DMF) in female Wistar rats, and to provide experimental data for the overall evaluation of DMF toxicity under different ways of exposure. Forty female Wistar rats weighing 150∼180 g were randomly divided into four groups: control group (treated with water) and three DMF exposure groups with doses of 50 mg/kg, 100 mg/kg, and 200 mg/kg. After oral administration of DMF once a day for 14 consecutive days, the rats were weighed and sacrificed. The liver, kidney, brain, and uterus were weighed to calculate organ indices. The pathological changes in the liver were examined by HE staining. The protein expression of HSP70 in the liver, kidney, and brain was determined. Finally, peripheral lymphocytes were collected from the arteria cruralis to determine DNA damage by comet assay. Fourteen days after DMF exposure, the body weight and organ indices of the kidney, brain, and uterus showed no significant changes. However, the liver index showed concentration-dependent increase in all DMF exposed groups (3.52±0.21, 3.55±0.13, and 3.88±0.22 in the low-, medium-, and high-dose groups, respectively), as compared with the control group (3.24±0.28) (P < 0.05 or P < 0.01). The pathological damage in the liver also showed a concentration-dependent manner. Inflammatory cell infiltration and granular degeneration in centrilobular hepatocytes were observed in the high-dose group. No significant change in protein expression of HSP70 was observed in the liver, kidney, or brain of DMF-exposed rats (P > 0.05). DNA damage was induced by DMF, and the DNA percentage of lymphocyte comet tail, average tail length, and tail moment in exposed groups were all significantly increased as compared with the control group (P < 0.05 or P < 0.01). Gavaged DMF can induce liver injury and DNA damage in lymphocytes in rats 14 days after administration. There is no significant change in protein expression of HSP70 in the liver, brain, or kidney after DMF exposure.