61,111 research outputs found
Stable Matching with Evolving Preferences
We consider the problem of stable matching with dynamic preference lists. At
each time step, the preference list of some player may change by swapping
random adjacent members. The goal of a central agency (algorithm) is to
maintain an approximately stable matching (in terms of number of blocking
pairs) at all times. The changes in the preference lists are not reported to
the algorithm, but must instead be probed explicitly by the algorithm. We
design an algorithm that in expectation and with high probability maintains a
matching that has at most blocking pairs.Comment: 13 page
Aggregating partial, local evaluations to achieve global ranking
We analyze some voting models mimicking online evaluation systems intended to
reduce the information overload. The minimum number of operations needed for a
system to be effective is analytically estimated. When herding effects are
present, linear preferential attachment marks a transition between trustful and
biased reputations.Comment: 9 pages, 5 figures, accepted for publication in Physica
Stepping Stones to Inductive Synthesis of Low-Level Looping Programs
Inductive program synthesis, from input/output examples, can provide an
opportunity to automatically create programs from scratch without presupposing
the algorithmic form of the solution. For induction of general programs with
loops (as opposed to loop-free programs, or synthesis for domain-specific
languages), the state of the art is at the level of introductory programming
assignments. Most problems that require algorithmic subtlety, such as fast
sorting, have remained out of reach without the benefit of significant
problem-specific background knowledge. A key challenge is to identify cues that
are available to guide search towards correct looping programs. We present
MAKESPEARE, a simple delayed-acceptance hillclimbing method that synthesizes
low-level looping programs from input/output examples. During search, delayed
acceptance bypasses small gains to identify significantly-improved stepping
stone programs that tend to generalize and enable further progress. The method
performs well on a set of established benchmarks, and succeeds on the
previously unsolved "Collatz Numbers" program synthesis problem. Additional
benchmarks include the problem of rapidly sorting integer arrays, in which we
observe the emergence of comb sort (a Shell sort variant that is empirically
fast). MAKESPEARE has also synthesized a record-setting program on one of the
puzzles from the TIS-100 assembly language programming game.Comment: AAAI 201
Fluctuations of fragment observables
This contribution presents a review of our present theoretical as well as
experimental knowledge of different fluctuation observables relevant to nuclear
multifragmentation. The possible connection between the presence of a
fluctuation peak and the occurrence of a phase transition or a critical
phenomenon is critically analyzed. Many different phenomena can lead both to
the creation and to the suppression of a fluctuation peak. In particular, the
role of constraints due to conservation laws and to data sorting is shown to be
essential. From the experimental point of view, a comparison of the available
fragmentation data reveals that there is a good agreement between different
data sets of basic fluctuation observables, if the fragmenting source is of
comparable size. This compatibility suggests that the fragmentation process is
largely independent of the reaction mechanism (central versus peripheral
collisions, symmetric versus asymmetric systems, light ions versus heavy ion
induced reactions). Configurational energy fluctuations, that may give
important information on the heat capacity of the fragmenting system at the
freeze out stage, are not fully compatible among different data sets and
require further analysis to properly account for Coulomb effects and secondary
decays. Some basic theoretical questions, concerning the interplay between the
dynamics of the collision and the fragmentation process, and the cluster
definition in dense and hot media, are still open and are addressed at the end
of the paper. A comparison with realistic models and/or a quantitative analysis
of the fluctuation properties will be needed to clarify in the next future the
nature of the transition observed from compound nucleus evaporation to
multi-fragment production.Comment: Contribution to WCI (World Consensus Initiative) Book " "Dynamics and
Thermodynamics with Nuclear Degrees of Freedom", to appear on Euorpean
Physics Journal A as part of the Topical Volume. 9 pages, 12 figure
Metaheuristic design of feedforward neural networks: a review of two decades of research
Over the past two decades, the feedforward neural network (FNN) optimization has been a key interest among the researchers and practitioners of multiple disciplines. The FNN optimization is often viewed from the various perspectives: the optimization of weights, network architecture, activation nodes, learning parameters, learning environment, etc. Researchers adopted such different viewpoints mainly to improve the FNN's generalization ability. The gradient-descent algorithm such as backpropagation has been widely applied to optimize the FNNs. Its success is evident from the FNN's application to numerous real-world problems. However, due to the limitations of the gradient-based optimization methods, the metaheuristic algorithms including the evolutionary algorithms, swarm intelligence, etc., are still being widely explored by the researchers aiming to obtain generalized FNN for a given problem. This article attempts to summarize a broad spectrum of FNN optimization methodologies including conventional and metaheuristic approaches. This article also tries to connect various research directions emerged out of the FNN optimization practices, such as evolving neural network (NN), cooperative coevolution NN, complex-valued NN, deep learning, extreme learning machine, quantum NN, etc. Additionally, it provides interesting research challenges for future research to cope-up with the present information processing era
Ringing the eigenmodes from compact manifolds
We present a method for finding the eigenmodes of the Laplace operator acting
on any compact manifold. The procedure can be used to simulate cosmic microwave
background fluctuations in multi-connected cosmological models. Other
applications include studies of chaotic mixing and quantum chaos.Comment: 11 pages, 8 figures, IOP format. To be published in the proceedings
of the Cleveland Cosmology and Topology Workshop 17-19 Oct 1997. Submitted to
Class. Quant. Gra
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