An empirical Evaluation of a General Purpose Automated Order Accumulation and Sortation System used in Batch Picking

AbstractA classic problem in parallel computing is determining whether to execute a thread in parallel or sequentially. If small threads are executed in parallel, the overheads due to thread creation can overwhelm the benefits of parallelism, resulting in suboptimal efficiency and performance. If large threads are executed sequentially, processors may spin idle, resulting again in sub-optimal efficiency and performance. This “granularity problem” is especially important in implicitly parallel languages, where the programmer expresses all potential for parallelism, leaving it to the system to exploit parallelism by creating threads as necessary. Although this problem has been identified as an important problem, it is not well understood—broadly applicable solutions remain elusive. In this paper, we propose techniques for automatically controlling granularity in implicitly parallel programming languages to achieve parallel efficiency and performance. To this end, we first extend a classic result, Brent's theorem (a.k.a. the work-time principle) to include thread-creation overheads. Using a cost semantics for a general-purpose language in the style of lambda calculus with parallel tuples, we then present a precise accounting of thread-creation overheads and bound their impact on efficiency and performance. To reduce such overheads, we propose an oracle-guided semantics by using estimates of the sizes of parallel threads. We show that, if the oracle provides accurate estimates in constant time, then the oracle-guided semantics reduces the thread-creation overheads for a reasonably large class of parallel computations. We describe how to approximate the oracle-guided semantics in practice by combining static and dynamic techniques. We require the programmer to provide the asymptotic complexity cost for each parallel thread and use runtime profiling to determine hardware-specific constant factors. We present an implementation of the proposed approach as an extension of the Manticore compiler for Parallel ML. Our empirical evaluation shows that our techniques can reduce thread-creation overheads, leading to good efficiency and performance.

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Pattern-Based Approach to the Workflow Satisfiability Problem with User-Independent Constraints

Journal of Artificial Intelligence Research ◽

10.1613/jair.1.11339 ◽

2019 ◽

Vol 66 ◽

pp. 85-122 ◽

Cited By ~ 1

Author(s):

Daniel Karapetyan ◽

Andrew J. Parkes ◽

Gregory Gutin ◽

Andrei Gagarin

Keyword(s):

Computational Study ◽

Empirical Evaluation ◽

Practical Interest ◽

General Purpose ◽

Satisfiability Problem ◽

Polynomial Space ◽

Fixed Parameter Tractable ◽

Fpt Algorithms ◽

Fpt Algorithm ◽

New Interpretation

The fixed parameter tractable (FPT) approach is a powerful tool in tackling computationally hard problems. In this paper, we link FPT results to classic artificial intelligence (AI) techniques to show how they complement each other. Specifically, we consider the workflow satisfiability problem (WSP) which asks whether there exists an assignment of authorised users to the steps in a workflow specification, subject to certain constraints on the assignment. It was shown by Cohen et al. (JAIR 2014) that WSP restricted to the class of user-independent constraints (UI), covering many practical cases, admits FPT algorithms, i.e. can be solved in time exponential only in the number of steps k and polynomial in the number of users n. Since usually k << n in WSP, such FPT algorithms are of great practical interest. We present a new interpretation of the FPT nature of the WSP with UI constraints giving a decomposition of the problem into two levels. Exploiting this two-level split, we develop a new FPT algorithm that is by many orders of magnitude faster than the previous state-of-the-art WSP algorithm and also has only polynomial-space complexity. We also introduce new pseudo-Boolean (PB) and Constraint Satisfaction (CSP) formulations of the WSP with UI constraints which efficiently exploit this new decomposition of the problem and raise the novel issue of how to use general-purpose solvers to tackle FPT problems in a fashion that meets FPT efficiency expectations. In our computational study, we investigate, for the first time, the phase transition (PT) properties of the WSP, under a model for generation of random instances. We show how PT studies can be extended, in a novel fashion, to support empirical evaluation of scaling of FPT algorithms.

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Simple Energy Aware Scheduler: An Empirical Evaluation

CLEI electronic journal ◽

10.19153/cleiej.21.2.8 ◽

2018 ◽

Vol 21 (2) ◽

Author(s):

Alexander Perez Campos ◽

Juan Manuel Rodriguez ◽

Alejandro Zunino

Keyword(s):

Distributed Computing ◽

Mobile Devices ◽

Job Scheduling ◽

Research Work ◽

Empirical Evaluation ◽

Real Life ◽

General Purpose ◽

Energy Aware ◽

Computing Platform ◽

Accessible Information

Mobile devices have evolved from single purpose devices, such as mobile phone, into general purpose multi-core computers with considerable unused capabilities. Therefore, several researchers have considered harnessing the power of these battery-powered devices for distributed computing. Despite their ever-growing capabilities, using battery as power source for mobile devices represents a major challenge for applying traditional distributed computing techniques. Particularly, researchers aimed at using mobile devices as resources for executing computationally intensive task. Different job scheduling algorithms were proposed with this aim, but many of them require information that is unavailable or difficult to obtain in real-life environments, such as how much energy would require a job to be finished. In this context, Simple Energy Aware Scheduler (SEAS) is a scheduling technique for computational intensive Mobile Grids that only require easily accessible information. It was proposed in 2010 and it has been the base for a range of research work. Despite being described as easily implementable in real-life scenarios, SEAS and other SEAS-improvements works have always been evaluated using simulations. In this work, we present a distributed computing platform for mobile devices that support SEAS and empirical evaluation of the SEAS scheduler. This evaluation followed the methodology of the original SEAS evaluation, in which Random and Round Robin schedulers were used as baselines. Although the original evaluation was performed by simulation using notebooks profile instead of smartphones and tablets, results confirms that SEAS outperforms the baseline schedulers.

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