Communication models insights meet simulations

International audienceIt is well-known that taking into account communications while scheduling jobs in large scale parallel computing platforms is a crucial issue. In modern hierarchical platforms, communication times are highly different when occurring inside a cluster or between clusters. Thus, allocating the jobs taking into account locality constraints is a key factor for reaching good performances. However, several theoretical results prove that imposing such constraints reduces the solution space and thus, possibly degrades the performances. In practice, such constraints simplify implementations and most often lead to better results. Our aim in this work is to bridge theoretical and practical intuitions, and check the differences between constrained and unconstrained schedules (namely with respect to locality and node contiguity) through simulations. We have developped a generic tool, using SimGrid as the base simulator, enabling interactions with external batch schedulers to evaluate their scheduling policies. The results confirm that insights gained through theoretical models are ill-suited to current architectures and should be reevaluated

Batsim: a Realistic Language-Independent Resources and Jobs Management Systems Simulator

International audienceAs large scale computation systems are growing to exascale, Resources and Jobs Management Systems (RJMS) need to evolve to manage this scale modification. However, their study is problematic since they are critical production systems, where experimenting is extremely costly due to downtime and energy costs. Meanwhile, many scheduling algorithms emerging from theoretical studies have not been transferred to production tools for lack of realistic experimental validation. To tackle these problems we propose Batsim, an extendable, language-independent and scalable RJMS simulator. It allows researchers and engineers to test and compare any scheduling algorithm, using a simple event-based communication interface, which allows different levels of realism. In this paper we show that Batsim's behaviour matches the one of the real RJMS OAR. Our evaluation process was made with reproducibility in mind and all the experiment material is freely available

Batsim: a Realistic Language-Independent Resources and Jobs Management Systems Simulator

International audienceAs large scale computation systems are growing to exascale, Resources and Jobs Management Systems (RJMS) need to evolve to manage this scale modification. However, their study is problematic since they are critical production systems, where experimenting is extremely costly due to downtime and energy costs. Meanwhile, many scheduling algorithms emerging from theoretical studies have not been transferred to production tools for lack of realistic experimental validation. To tackle these problems we propose Batsim, an extendable, language-independent and scalable RJMS simulator. It allows researchers and engineers to test and compare any scheduling algorithm, using a simple event-based communication interface, which allows different levels of realism. In this paper we show that Batsim's behaviour matches the one of the real RJMS OAR. Our evaluation process was made with reproducibility in mind and all the experiment material is freely available

Efficient processor allocation strategies for mesh-connected multicomputers

Abstract Efficient processor allocation and job scheduling algorithms are critical if the full computational power of large-scale multicomputers is to be harnessed effectively. Processor allocation is responsible for selecting the set of processors on which parallel jobs are executed, whereas job scheduling is responsible for determining the order in which the jobs are executed. Many processor allocation strategies have been devised for mesh-connected multicomputers and these can be divided into two main categories: contiguous and non-contiguous. In contiguous allocation, jobs are allocated distinct contiguous processor sub-meshes for the duration of their execution. Such a strategy could lead to high processor fragmentation which degrades system performance in terms of, for example, the turnaround time and system utilisation. In non-contiguous allocation, a job can execute on multiple disjoint smaller sub-meshes rather than waiting until a single sub-mesh of the requested size and shape is available. Although non-contiguous allocation increases message contention inside the network, lifting the contiguity condition can reduce processor fragmentation and increase system utilisation. Processor fragmentation can be of two types: internal and external. The former occurs when more processors are allocated to a job than it requires while the latter occurs when there are free processors enough in number to satisfy another job request, but they are not allocated to it because they are not contiguous. A lot of efforts have been devoted to reducing fragmentation, and a number of contiguous allocation strategies have been devised to recognize complete sub-meshes during allocation. Most of these strategies have been suggested for 2D mesh-connected multicomputers. However, although the 3D mesh has been the underlying network topology for a number of important multicomputers, there has been relatively little activity with regard to designing similar strategies for such a network. The very few contiguous allocation strategies suggested for the 3D mesh achieve complete sub-mesh recognition ability only at the expense of a high allocation overhead (i.e., allocation and de-allocation time). Furthermore, the allocation overhead in the existing contiguous strategies often grows with system size. The main challenge is therefore to devise an efficient contiguous allocation strategy that can exhibit good performance (e.g., a low job turnaround time and high system utilisation) with a low allocation overhead. The first part of the research presents a new contiguous allocation strategy, referred to as Turning Busy List (TBL), for 3D mesh-connected multicomputers. The TBL strategy considers only those available free sub-meshes which border from the left of those already allocated sub-meshes or which have their left boundaries aligned with that of the whole mesh network. Moreover TBL uses an efficient scheme to facilitate the detection of such available sub-meshes while maintaining a low allocation overhead. This is achieved through maintaining a list of allocated sub-meshes in order to efficiently determine the processors that can form an allocation sub-mesh for a new allocation request. The new strategy is able to identify a free sub-mesh of the requested size as long as it exists in the mesh. Results from extensive simulations under various operating loads reveal that TBL manages to deliver competitive performance (i.e., low turnaround times and high system utilisation) with a much lower allocation overhead compared to other well-known existing strategies. Most existing non-contiguous allocation strategies that have been suggested for the mesh suffer from several problems that include internal fragmentation, external fragmentation, and message contention inside the network. Furthermore, the allocation of processors to job requests is not based on free contiguous sub-meshes in these existing strategies. The second part of this research proposes a new non-contiguous allocation strategy, referred to as Greedy Available Busy List (GABL) strategy that eliminates both internal and external fragmentation and alleviates the contention in the network. GABL combines the desirable features of both contiguous and non-contiguous allocation strategies as it adopts the contiguous allocation used in our TBL strategy. Moreover, GABL is flexible enough in that it could be applied to either the 2D or 3D mesh. However, for the sake of the present study, the new non-contiguous allocation strategy is discussed for the 2D mesh and compares its performance against that of well-known non-contiguous allocation strategies suggested for this network. One of the desirable features of GABL is that it can maintain a high degree of contiguity between processors compared to the previous allocation strategies. This, in turn, decreases the number of sub-meshes allocated to a job, and thus decreases message distances, resulting in a low inter-processor communication overhead. The performance analysis here indicates that the new proposed strategy has lower turnaround time than the previous non-contiguous allocation strategies for most considered cases. Moreover, in the presence of high message contention due to heavy network traffic, GABL exhibits superior performance in terms of the turnaround time over the previous contiguous and non-contiguous allocation strategies. Furthermore, GABL exhibits a high system utilisation as it manages to eliminate both internal and external fragmentation. The performance of many allocation strategies including the ones suggested above, has been evaluated under the assumption that job execution times follow an exponential distribution. However, many measurement studies have convincingly demonstrated that the execution times of certain computational applications are best characterized by heavy-tailed job execution times; that is, many jobs have short execution times and comparatively few have very long execution times. Motivated by this observation, the final part of this thesis reviews the performance of several contiguous allocation strategies, including TBL, in the context of heavy-tailed distributions. This research is the first to analyze the performance impact of heavy-tailed job execution times on the allocation strategies suggested for mesh-connected multicomputers. The results show that the performance of the contiguous allocation strategies degrades sharply when the distribution of job execution times is heavy-tailed. Further, adopting an appropriate scheduling strategy, such as Shortest-Service-Demand (SSD) as opposed to First-Come-First-Served (FCFS), can significantly reduce the detrimental effects of heavy-tailed distributions. Finally, while the new contiguous allocation strategy (TBL) is as good as the best competitor of the previous contiguous allocation strategies in terms of job turnaround time and system utilisation, it is substantially more efficient in terms of allocation overhead

Mapping and Scheduling HPC Applications for Optimizing I/O

The premier international forum for the presentation of research results in HPC systems, will be VIRTUALLY held in Barcelona, SpainInternational audienceIn HPC platforms, concurrent applications are sharing the same file system. This can lead to conflicts, especially as applications are more and more data intensive. I/O contention can represent a performance bottleneck. The access to bandwidth can be split in two complementary yet distinct problems. The mapping problem and the scheduling problem. The mapping problem consists in selecting the set of applications that are in competition for the I/O resource. The scheduling problem consists then, given I/O requests on the same resource, in determining the order to these accesses to minimize the I/O time. In this work we propose to couple a novel bandwidth-aware mapping algorithm to I/O list-scheduling policies to develop a cross-layer optimization solution. We study this solution experimentally using an I/O middleware: CLARISSE. We show that naive policies such as FIFO perform relatively well in order to schedule I/O movements, and that the important part to reduce congestion lies mostly on the mapping part. We evaluate the algorithm that we propose using a simulator that we validated experimentally. This evaluation shows important gains for the simple, bandwidth-aware mapping solution that we provide compared to its non bandwidth-aware counterpart. The gains are both in terms of machine efficiency (makespan) and application efficiency (stretch). This stresses even more the importance of designing efficient, bandwidth-aware mapping strategies to alleviate the cost of I/O congestion

Texas Register

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code

Topology Agnostic Methods for Routing, Reconfiguration and Virtualization of Interconnection Networks

Modern computing systems, such as supercomputers, data centers and multicore chips, generally require efficient communication between their different system units; tolerance towards component faults; flexibility to expand or merge; and a high utilization of their resources. Interconnection networks are used in a variety of such computing systems in order to enable communication between their diverse system units. Investigation and proposal of new or improved solutions to topology agnostic routing and reconfiguration of interconnection networks are main objectives of this thesis. In addition, topology agnostic routing and reconfiguration algorithms are utilized in the development of new and flexible approaches to processor allocation. The thesis aims to present versatile solutions that can be used for the interconnection networks of a number of different computing systems. No particular routing algorithm was specified for an interconnection network technology which is now incorporated in Dolphin Express. The thesis states a set of criteria for a suitable routing algorithm, evaluates a number of existing routing algorithms, and recommend that one of the algorithms – which fulfils all of the criteria – is used. Further investigations demonstrate how this routing algorithm inherently supports fault-tolerance, and how it can be optimized for some network topologies. These considerations are also relevant for the InfiniBand interconnection network technology. Reconfiguration of interconnection networks (change of routing function) is a deadlock prone process. Some existing reconfiguration strategies include deadlock avoidance mechanisms that significantly reduce the network service offered to running applications. The thesis expands the area of application for one of the most versatile and efficient reconfiguration algorithms available in the literature, and proposes an optimization of this algorithm that improves the network service offered to running applications. Moreover, a new reconfiguration algorithm is presented that supports a replacement of the routing function without causing performance penalties. Processor allocation strategies that guarantee traffic-containment commonly pose strict requirements on the shape of partitions, and thus achieve only a limited utilization of a system’s computing resources. The thesis introduces two new approaches that are more flexible. Both approaches utilize the properties of a topology agnostic routing algorithm in order to enforce traffic-containment within arbitrarily shaped partitions. Consequently, a high resource utilization as well as isolation of traffic between different partitions is achieved

Site Structure And Organization In Central Alaska: Archaeological Investigations At Gerstle River

Thesis (Ph.D.) University of Alaska Fairbanks, 2005This dissertation presents a multi-dimensional analysis of site structure and organization at a multi-component deeply buried stratified site in the Tanana Basin in Interior Alaska, Gerstle River. The primary objective of this research is to investigate patterning among the lithics, fauna, features, stratigraphy, and radiometric dating, within and among components and intra-component hierarchical spatial aggregates. These analyses are situated within and are explored in terms of technological and spatial organization. Given the longevity of microblade technology (12000 BP to ~1000 BP) and its presence in very different climatic and biotic regimes, understanding how microblades were used within a technological system and possible variations in microblade use could be useful in understanding technological change during the Pleistocene-Holocene transition and later Holocene times. This research analyzes microblades and other lithic classes at a number of levels (e.g., attribute, artifact, raw material, modification type, cluster, area, component, and site). Results show a number of organizational properties used by Early Holocene populations at Gerstle River, providing a dataset useful for testing future models derived from experimental, ethnoarchaeological, and other middle range approaches. Patterns of technology and technological organization are more highly resolved when incorporating spatial analyses. Microblade technology is shown to be structurally complex, used for a variety of purposes and reflecting different stages of production and different modes of use and disposal, including microblade production, replacement, and discard. Inferences about faunal procurement, subsistence, transport decisions, settlement patterns, and economy are made through a multidimensional faunal analysis. Non-human factors were not major agents in the formation of the assemblages. A spatial model of faunal processing indicates how space was used in processing multiple individuals of wapiti and bison. Contextual data from lithic technology, faunal remains, features, radiocarbon dating, and spatial relationships are used to model several dimensions of organization present at Gerstle River, including site activities, technological organization, disposal modes, organization of space, redundancy, storage, seasonality, location, group size and economic structure, economy, and settlement system

CACIC 2015 : XXI Congreso Argentino de Ciencias de la Computación. Libro de actas

Actas del XXI Congreso Argentino de Ciencias de la Computación (CACIC 2015), realizado en Sede UNNOBA Junín, del 5 al 9 de octubre de 2015.Red de Universidades con Carreras en Informática (RedUNCI

Establishing criteria for descriptions of building work which include practicality and intricacy

In the UK construction industry, descriptions of work are the facilitators for passing of information across a wide spectrum of users. It is thought generally that the descriptions of work produced by quantity surveyors and employed in the contract documentation are sufficient to enable cost information to be transmitted to all participants. Nonetheless, to the contractor, cost is a variable with many different unknowns, but to the client cost is a constant based upon the contractors’ legally enforceable prices, subject to such controlled variations as an ‘increased cost’ clause. The purpose, however, is the same for both parties. Given that situation, it might be thought that it is essential for both parties to be provided with full and accurate information so that the estimate produced can be as near as possible to the final account figure. The producers of building work descriptions are employed by the clients (it was not always so), the information content of descriptions can omit items that are not relevant to clients’ costs without having to consider whether contractors’ costs are affected, and they are the sole arbiters of what is relevant. The consequence is that descriptions supplied to contractors do not reflect fully the intricacy of the work or the practical needs of those involved in production. This study began because it was realised that descriptions of building works do not describe the physical work of the labour and plant involved, they only describe materials. With this in mind, the study aims to develop criteria for a method of describing building work which reflects production and facilitates feedback, not only of basic costs, but also of the intricacies which cause differences in cost. This study initially traces the development of the rules for transmitting information supplied to contractors showing how their purpose, and hence their content, has altered during the century of their existence. This was carried out by examining the existing method of measurement (from which current descriptions are derived) by comparing each edition with the next in sequence to discover what is not measured and hence not described. The second phase of the study used a multiple case study method by observing work being carried out on site to see what is and is not measured or described and then reconciling the work carried out on site with the current edition of the Standard Method of Measurement /New Rules of Measurement. Twelve workpieces (cases) across two construction sites were analysed against relevant clauses and descriptions in order to develop criteria for describing building work. The study has found, or, rather, confirmed, that current written information-passing methods do not describe physical work, in fact they make every effort not to describe it. The changes in later editions of SMMs have diluted the content to the point where there is little or no thought given to contractors’ requirement for information. Furthermore, it is argued that the building needs to be thought of as a large number of pieces of work. Based on this, criteria have been developed that provide a method of describing work which allows for intricacies of the work to be indicated whilst also facilitating feedback of cost-causing data. The newly developed criteria point out the need for the results of work, the workpieces, to be the focus of description, at a fine level of detail rather than the somewhat impressionistic viewpoint of architects’ elements. This study challenges the current unstated theory that measurement of materials is the only way to produce accurate building prices, and proposes these criteria for describing building work, with ‘workpiece’ at the heart of each description