Loops take up most of the time of computer programs, so optimizing them so that they run in the shortest time possible is a continuous task. However, this task is not negligible; on the contrary, it ...is an open area of research since many irregular loops are hard to parallelize. Generally, these loops have loop-carried (DOACROSS) dependencies and the appearance of dependencies could depend on the context. Many techniques have been studied to be able to parallelize these loops efficiently; however, for example in the OpenMP standard there is no efficient way to parallelize them. This article presents Speculative Task Execution (STE), a technique that enables the execution of OpenMP tasks in a speculative way to accelerate certain hot-code regions (such as loops) marked by OpenMP directives. It also presents a detailed analysis of the application of Hardware Transactional Memory (HTM) support for executing tasks speculatively and describes a careful evaluation of the implementation of STE using HTM on modern machines. In particular, we consider the scenario in which speculative tasks are generated by the OpenMP taskloop construct (Speculative Taskloop (STL)). As a result, it provides evidence to support several important claims about the performance of STE over HTM in modern processor architectures. Experimental results reveal that: (a) by implementing STL on top of HTM for hot-code regions, speed-ups of up to 5.39× can be obtained in IBM POWER8 and of up to 2.41× in Intel processors using 4 cores; and (b) STL-ROT, a variant of STL using rollback-only transactions (ROTs), achieves speed-ups of up to 17.70× in IBM POWER9 processor using 20 cores.
•Proposal of STE/STL to parallelize loops using HTM’s speculative-execution support.•Modification of the LLVM OpenMP Runtime Library to support monotonic scheduling.•In-depth evaluation of STL on an Intel processor with TSX-NI support.•Comparison of the performance of STL and FOR-TLS using an IBM POWER8 processor.•Assessment of the performance of Speculative Taskloop (with the optimized OpenMP Runtime Library) and FOR-TLS using an IBM POWER8 processor. The results show the potential of the technique when aborts due to order-inversion are mitigated.•Proposal and evaluation of STL-ROT by comparing it to STL using IBM POWER machines.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Seamless application execution is vital for the usability of various delay-sensitive mobile cloud applications. However, the resource-intensive migration process and intrinsic limitations of the ...wireless medium impede the realization of seamless execution in mobile cloud computing (MCC) environment. This work is the first comprehensive survey that studies the state-of-the-art cloud-based mobile application execution frameworks (CMAEFs) in perspective of seamless application execution in MCC and investigates the frameworks suitability for the seamless execution. The seamless execution enabling approaches for the CMAEFs are identified and classified based on the implementation locations. We also investigate the seamless application execution enabling approaches to identify advantages and disadvantages of employing such approaches for attaining the seamless application execution in MCC. The existing frameworks are compared based on the significant parameters derived from the taxonomy of the seamless application execution enabling approaches. The principles for enabling the seamless application execution within the MCC are also highlighted. Finally, open research challenges in realizing the seamless application execution are discussed.
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In today's volatile, uncertain, and complex business environments, manufacturing companies must not only adapt to market demands but also minimize the time between problem occurrence and resolution. ...The implementation of lean manufacturing systems has been crucial in this regard. However, traditional approaches have shown notable inefficiencies that can be effectively addressed through digitalization. By embracing digital solutions, manufacturing companies can ensure efficient continuous improvement, driving performance to higher levels. This study aims to find a digital solution for a specific company that faces daily challenges associated with low visibility into production. An investigation revealed that the Lean tools used by the company were outdated, directly affecting the generated information and consequently, decision-making. The integration of a Manufacturing Execution System into the factory's dynamics was the solution found. In this context, a step-by-step methodology is proposed to guide the implementation. As a result, a prototype of the system was designed. The validation of the system by end-users demonstrates the success of the proposed methodology.
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Processing large scientific applications generates a huge amount of data, which makes running experiments in the cloud computing environment very expensive and energy-consuming. To find an optimal ...solution to the workflow scheduling problem, several approaches have been presented for scheduling workflow on cloud resources. However, more efficient approaches are needed to improve cloud service delivery. In this paper, an energy-efficient virtual machine mapping algorithm (EViMA) is proposed to improve resource management in the cloud computing environment to achieve effective scheduling that reduces cloud data center energy consumption, execution makespan, and execution cost. This ensures that the requirements of cloud users are met, and improves the quality of services offered by cloud providers. Our proposed mechanism considers the heterogeneity of scheduling from both cloud users’ and workflow applications’ perspectives. Through simulation experiments on real workflow datasets, the proposed EViMA can provide better solutions for both cloud users and cloud providers by reducing energy consumption, execution makespan, and execution cost better than the state-of-the-art.
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Sharding is a promising solution to enhance the scalability of blockchain. However, previous sharding systems adopt the lock-based cross-shard protocol to exclusively handle one-shot cross-shard ...transactions, leading to low-efficiency executions and unavailable calls when handling complex cross-shard contracts that introduce multi-shot cross-shard transactions to invoke multiple contracts managed by different shards. In this paper, we aim to enable efficient execution of arbitrarily complex cross-shard contracts in blockchain sharding systems. First, we perform a calling-flow analysis on Ethereum contracts with more than 180 million real-world transactions and find that about <inline-formula><tex-math notation="LaTeX">30\%</tex-math> <mml:math><mml:mn>30</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math><inline-graphic xlink:href="zhang-ieq1-3365929.gif"/> </inline-formula> transactions invoke complex contracts. Then, motivated by the properties of these complex contracts, we propose an off-chain execution model, called ShardCon, to achieve efficient executions for complex cross-shard contracts by decoupling the contract execution from the cross-shard consensus. Next, we introduce a cross-shard contract execution engine and a contract-driven deployment rule to the overheads introduced by off-chain executions. Moreover, to adapt to the multi-chain property of a sharding system, we introduce an off-chain state atomic commit protocol. Finally, we implement a prototype and evaluate it with concrete cross-shard contracts, showing that ShardCon can achieve more than 10x increase in throughput and 2x decrease in confirmation latency than the state-of-the-art sharding systems.
This study aimed to analyze the authority of the fiduciary beneficiary creditor whose object was a building that stands on the land of management rights over city government and legal certainty of ...loan repayment if the debtor defaults on the fiduciary guarantee. This study used a conceptual and legal approach with a normative juridical type of research. The study results indicated that the authority of the fiduciary beneficiary creditor, whose object was a building that stands on land with the management rights of the city government, was to extend it if the term of the land use permit had expired. The creditor had the right to execute or sell the object of the fiduciary guarantee on the creditor's power if the debtor could not fulfill his obligations. When the debtor defaults, legal certainty for creditors receiving fiduciary guarantees to recover their receivables were applied for execution through a district court based on the executorial title contained in the fiduciary guarantee certificate.
Simple Temporal Networks (STNs) are a well-studied model for representing temporal constraints. They comprise a set of time-points (real-valued variables representing execution times) and binary ...difference constraints among them. Simple Temporal Networks with Uncertainty (STNUs) extend STNs in that some time-points (called contingent) are treated as exogenous variables, whose execution times, bound to fall within a given interval from the corresponding activation time-points (as specified by a “contingent link”), get revealed only during real-time execution. An STNU is dynamically controllable (DC) if there exists a strategy to execute its time-points satisfying all the constraints, regardless of the execution times of contingent time-points revealed during execution.
In this work we present a new system of constraint propagation rules for STNUs, which is sound-and-complete for DC checking. Our system comprises just three rules which, differently from the ones proposed in all previous works, only generate unconditioned constraints. In particular, after applying any of our rules, the network remains an STNU in all respects. Moreover, our completeness proof is short and non-algorithmic, based on the explicit construction of a valid execution strategy. This is a substantial simplification of the theory which underlies all the previous efficient algorithms for DC-checking.
Our analysis also shows: (1) the existence of late execution strategies for STNUs, (2) the equivalence of the notion of DC among several variants of the semantics of STNUs, (3) the existence of a fast algorithm for real-time execution of STNUs, which runs in O(KN) total time in a network with K≥1 contingent links and N≥K time points, considerably improving the previous O(N3)-time bound.
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IoT-driven intelligent transportation systems (ITS) have great potential and capacity to make transportation systems efficient, safe, smart, reliable, and sustainable. The IoT provides the access and ...driving forces of seamlessly integrating transportation systems from the physical world to the virtual counterparts in the cyber world. In this paper, we present visions and works on integrating the artificial intelligent transportation systems and the real intelligent transportation systems to create and enhance "intelligence" of IoT-enabled ITS. With the increasing ubiquitous and deep sensing capacity of IoT-enabled ITS, we can quickly create artificial transportation systems equivalent to physical transportation systems in computers, and thus have parallel intelligent transportation systems, i.e. the real intelligent transportation systems and artificial intelligent transportation systems. The evolution process of transportation system is studied in the view of the parallel world. We can use a large number of long-term iterative simulation to predict and analyze the expected results of operations. Thus, truly effective and smart ITS can be planned, designed, built, operated and used. The foundation of the parallel intelligent transportation systems is based on the ACP theory, which is composed of artificial societies, computational experiments, and parallel execution. We also present some case studies to demonstrate the effectiveness of parallel transportation systems.
Modern processors use branch prediction and speculative execution to maximize performance. For example, if the destination of a branch depends on a memory value that is in the process of being read, ...CPUs will try to guess the destination and attempt to execute ahead. When the memory value finally arrives, the CPU either discards or commits the speculative computation. Speculative logic is unfaithful in how it executes, can access the victim's memory and registers, and can perform operations with measurable side effects. Spectre attacks involve inducing a victim to speculatively perform operations that would not occur during correct program execution and which leak the victim's confidential information via a side channel to the adversary. This paper describes practical attacks that combine methodology from side channel attacks, fault attacks, and return-oriented programming that can read arbitrary memory from the victim's process. More broadly, the paper shows that speculative execution implementations violate the security assumptions underpinning numerous software security mechanisms, including operating system process separation, containerization, just-in-time (JIT) compilation, and countermeasures to cache timing and side-channel attacks. These attacks represent a serious threat to actual systems since vulnerable speculative execution capabilities are found in microprocessors from Intel, AMD, and ARM that are used in billions of devices. While makeshift processor-specific countermeasures are possible in some cases, sound solutions will require fixes to processor designs as well as updates to instruction set architectures (ISAs) to give hardware architects and software developers a common understanding as to what computation state CPU implementations are (and are not) permitted to leak.
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