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51.
Given a distributed system of \(n\) balls and \(n\) bins, how evenly can we distribute the balls to the bins, minimizing communication? The fastest non-adaptive and symmetric algorithm achieving a constant maximum bin load requires \(\varTheta (\log \log n)\) rounds, and any such algorithm running for \(r\in {\mathcal {O}}(1)\) rounds incurs a bin load of \(\varOmega ((\log n/\log \log n)^{1/r})\). In this work, we explore the fundamental limits of the general problem. We present a simple adaptive symmetric algorithm that achieves a bin load of 2 in \(\log ^* n+{\mathcal {O}}(1)\) communication rounds using \({\mathcal {O}}(n)\) messages in total. Our main result, however, is a matching lower bound of \((1-o(1))\log ^* n\) on the time complexity of symmetric algorithms that guarantee small bin loads. The essential preconditions of the proof are (i) a limit of \({\mathcal {O}}(n)\) on the total number of messages sent by the algorithm and (ii) anonymity of bins, i.e., the port numberings of balls need not be globally consistent. In order to show that our technique yields indeed tight bounds, we provide for each assumption an algorithm violating it, in turn achieving a constant maximum bin load in constant time. 相似文献
52.
M. Shamim Hossain Sandro Hardy Atif Alamri Abdulhameed Alelaiwi Verena Hardy Christoph Wilhelm 《Multimedia Systems》2016,22(6):659-674
Stroke is considered one of the main causes of death around the world. Survivors often suffer different kinds of disabilities in terms of their cognitive and motor capabilities, and are therefore unable to perform their day-to-day activities. To regain some of their cognitive as well as motor abilities, they require rehabilitation. To this end, we present a serious game framework based on augmented reality technology that may motivate the patients’ involvement in the rehabilitation exercise. Additionally, we analyze the requirements for such a framework and describe the concept and implementation of the proposed approach. Furthermore, we designed a wireless vibrotactile output device that is attached to a tangible object. The tangible object that is connected to the framework can give haptic as well as audio-visual feedback to the patient in a more motivating and entertaining environment for rehabilitation exercises. The suitability and utility of the proposed framework was evaluated with real stroke patients and compared against the performance of a healthy control group, thus facilitating occupational therapists in assessing a patient’s progress. Our evaluations show that the serious games with vibrotactile feedback are well accepted by patients. 相似文献
53.
Sarah Mostame Joonsuk Huh Christoph Kreisbeck Andrew J. Kerman Takatoshi Fujita Alexander Eisfeld Alán Aspuru-Guzik 《Quantum Information Processing》2017,16(2):44
With quantum computers being out of reach for now, quantum simulators are alternative devices for efficient and accurate simulation of problems that are challenging to tackle using conventional computers. Quantum simulators are classified into analog and digital, with the possibility of constructing “hybrid” simulators by combining both techniques. Here we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators. 相似文献
54.
Gabriele Kern-Isberner Marco Wilhelm Christoph Beierle 《Annals of Mathematics and Artificial Intelligence》2017,79(1-3):163-179
An often used methodology for reasoning with probabilistic conditional knowledge bases is provided by the principle of maximum entropy (so-called MaxEnt principle) that realises an idea of least amount of assumed information and thus of being as unbiased as possible. In this paper we exploit the fact that MaxEnt distributions can be computed by solving nonlinear equation systems that reflect the conditional logical structure of these distributions. We apply the theory of Gröbner bases that is well known from computational algebra to the polynomial system which is associated with a MaxEnt distribution, in order to obtain results for reasoning with maximum entropy. We develop a three-phase compilation scheme extracting from a knowledge base consisting of probabilistic conditionals the information which is crucial for MaxEnt reasoning and transforming it to a Gröbner basis. Based on this transformation, a necessary condition for knowledge bases to be consistent is derived. Furthermore, approaches to answering MaxEnt queries are presented by demonstrating how inferring the MaxEnt probability of a single conditional from a given knowledge base is possible. Finally, we discuss computational methods to establish general MaxEnt inference rules. 相似文献
55.
Christoph Bosshard Roland Bouffanais Michel Deville Ralf Gruber Jonas Latt 《Computers & Fluids》2011,44(1):1-8
In this paper, a comprehensive performance review of an MPI-based high-order three-dimensional spectral element method C++ toolbox is presented. The focus is put on the performance evaluation of several aspects with a particular emphasis on the parallel efficiency. The performance evaluation is analyzed with the help of a time prediction model based on a parameterization of the application and the hardware resources. Two tailor-made benchmark cases in computational fluid dynamics (CFD) are introduced and used to carry out this review, stressing the particular interest for clusters with up to thousands of cores. Some problems in the parallel implementation have been detected and corrected. The theoretical complexities with respect to the number of elements, to the polynomial degree, and to communication needs are correctly reproduced. It is concluded that this type of code has a nearly perfect speedup on machines with thousands of cores, and is ready to make the step to next-generation petaFLOP machines. 相似文献
56.
Matthias Jungmann Margarete Kopal Christoph ClauserThomas Berlage 《Computers & Geosciences》2011,37(4):541-553
Electrical borehole wall images represent micro-resistivity measurements at the borehole wall. The lithology reconstruction is often based on visual interpretation done by geologists. This analysis is very time-consuming and subjective. Different geologists may interpret the data differently. In this work, linear discriminant analysis (LDA) in combination with texture features is used for an automated lithology reconstruction of ODP (Ocean Drilling Program) borehole 1203A drilled during Leg 197. Six rock groups are identified by their textural properties in resistivity data obtained by a Formation MircoScanner (FMS). Although discriminant analysis can be used for multi-class classification, non-optimal decision criteria for certain groups could emerge. For this reason, we use a combination of 2-class (binary) classifiers to increase the overall classification accuracy. The generalization ability of the combined classifiers is evaluated and optimized on a testing dataset where a classification rate of more than 80% for each of the six rock groups is achieved. The combined, trained classifiers are then applied on the whole dataset obtaining a statistical reconstruction of the logged formation. Compared to a single multi-class classifier the combined binary classifiers show better classification results for certain rock groups and more stable results in larger intervals of equal rock type. 相似文献
57.
A popular approach in combinatorial optimization is to model problems as integer linear programs. Ideally, the relaxed linear
program would have only integer solutions, which happens for instance when the constraint matrix is totally unimodular. Still,
sometimes it is possible to build an integer solution with the same cost from the fractional solution. Examples are two scheduling
problems (Baptiste and Schieber, J. Sched. 6(4):395–404, 2003; Brucker and Kravchenko, J. Sched. 11(4):229–237, 2008) and the single disk prefetching/caching problem (Albers et al., J. ACM 47:969–986, 2000). We show that problems such as the three previously mentioned can be separated into two subproblems: (1) finding an optimal
feasible set of slots, and (2) assigning the jobs or pages to the slots. It is straigthforward to show that the latter can
be solved greedily. We are able to solve the former with a totally unimodular linear program, from which we obtain simple
combinatorial algorithms with improved worst case running time. 相似文献
58.
To generate artificial materials with advanced physical and chemical properties and to study phase transition kinetics on submillisecond time scale, an ultrafast nonadiabatic membrane nanocalorimeter was constructed. A set of commercially available membrane gauges for ultrafast nanocalorimetry has been developed. The gauges placed in a thermostat with controlled helium gas pressure and temperature can be utilized as devices for thermal processing and calorimetry with resolution of 1 nJ/K. Controlled ultrafast cooling, as well as heating, up to 10(6) K/s can be attained for nanogram samples. The maximum cooling rate is inversely proportional to the radius of the heated region of the gauge, which was in the range of 10-100 microm depending on the gauge. The minimum addenda heat capacity was 3 nJ/K. The dynamic heat-transfer problem for the temperature distribution in the membrane-gas system at ultrafast processing has been solved. The characteristic rate R(0) corresponding to quasistatic limit of the temperature change in the membrane-gas system has been found to be equal to 10(5) K/s for a 1 microm thick silicon nitride membrane in helium gas. Calorimeter performance at ultrafast rates has been verified by a set of test experiments. The method was applied for thermal processing and calorimetric measurements in a set of linear polymers. It has been established that nearly amorphous polyethylene can be obtained at a cooling rate of 10(6) K/s. 相似文献
59.
Since the various people involved in the design process for a building project tend to hold conflicting views, this inevitably
leads to a range of disparate models for planning and calculation purposes. In order to interpret the relevant geometrical,
topological and semantical data for any given building model, we identify a structural component graph, a graph of room faces,
a room graph and a relational object graph as aids and explain algorithms to derive these relations. We start with a building
model by transferring its geometrical, topological and semantical data into a volume model, decomposing the latter into a
so-called connection model and then extracting all air volume bodies and hulls of the model by means of further decomposition
into elementary cyclic connection components. The technique is demonstrated within the scope of building energy simulation
by deriving both a dimensionally reduced object model required for setting up a thermal multizone model and a geometrical
model for defining single or multiple computational fluid dynamic domains in a building together with incidence matrices correlating
these models. The algorithm is basically applicable to any building energy simulation tool.
相似文献
Ernst RankEmail: |
60.
Ordered binary decision diagrams are the state-of-the-art representation of switching functions. In order to keep the sizes of OBDDs tractable, heuristics and dynamic reordering algorithms are applied to optimize the underlying variable order. When finite state machines are represented by OBDDs the state encoding can be used as an additional optimization parameter. In this paper, we analyze local encoding transformations which can be applied dynamically. First, we investigate the potential of re-encoding techniques. We then propose the use of an XOR-transformation and show why this transformation is most suitable among the set of all encoding transformations. The presented theoretical framework establishes a new optimization technique for OBDDs. 相似文献