Do Accelerating Turing Machines Compute the Uncomputable?

Accelerating Turing machines have attracted much attention in the last decade or so. They have been described as “the work-horse of hypercomputation” (Potgieter and Rosinger 2010: 853). But do they really compute beyond the “Turing limit”—e.g., compute the halting function? We argue that the answer depends on what you mean by an accelerating Turing machine, on what you mean by computation, and even on what you mean by a Turing machine. We show first that in the current literature the term “accelerating Turing machine” is used to refer to two very different species of accelerating machine, which we call end-stage-in and end-stage-out machines, respectively. We argue that end-stage-in accelerating machines are not Turing machines at all. We then present two differing conceptions of computation, the internal and the external, and introduce the notion of an epistemic embedding of a computation. We argue that no accelerating Turing machine computes the halting function in the internal sense. Finally, we distinguish between two very different conceptions of the Turing machine, the purist conception and the realist conception; and we argue that Turing himself was no subscriber to the purist conception. We conclude that under the realist conception, but not under the purist conception, an accelerating Turing machine is able to compute the halting function in the external sense. We adopt a relatively informal approach throughout, since we take the key issues to be philosophical rather than mathematical.     

Coping knowledge boundaries between information system and business disciplines: An intellectual capital perspective

Information system development can be considered a collaboration between users and developers. The inability to leverage the localized knowledge embedded in these two stakeholders hinders software development work to achieve high performance. Exploring the ways to counter this difficulty is then critical. This study applies an intellectual capital perspective to address the issues around spanning the knowledge boundary between developers and users. Our findings highlighted how important effective knowledge boundary spanning is to both product and project quality. Furthermore, three dimensions of intellectual capital increased the degree to which knowledge boundary spanning was effective.     

Modelling of the interframe dependence in an HMM using conditional Gaussian mixtures

This paper investigates the modelling of the interframe dependence in a hidden Markov model (HMM) for speech recognition. First, a new observation model, assuming dependence on multiple previous frames, is proposed. This model represents such a dependence structure with a weighted mixture of a set of first-order conditional Gaussian densities, each mixture component accounting for a specific conditional frame. Next, an optimization in choosing the conditional frames/segment is performed in both training and recognition, thereby helping to remove the mismatch of the conditional segments due to different observation histories. An EM (Expectation–Maximization) iteration algorithm is developed for the estimation of the model parameters and for the optimization over the dependence structure. Experimental comparisons on a speaker-independent E-set database show that the new model, without optimization on the dependence structure, achieves better performance than the standard HMM, the bigram HMM and the linear-predictive HMM, all in comparable or smaller parameter sizes. The optimization over the dependence structure leads to further improvement in the performance.     

Unified model for assessing checkpointing protocols at extreme‐scale

In this paper, we present a unified model for several well‐known checkpoint/restart protocols. The proposed model is generic enough to encompass both extremes of the checkpoint/restart space, from coordinated approaches to a variety of uncoordinated checkpoint strategies (with message logging). We identify a set of crucial parameters, instantiate them, and compare the expected efficiency of the fault tolerant protocols, for a given application/platform pair. We then propose a detailed analysis of several scenarios, including some of the most powerful currently available high performance computing platforms, as well as anticipated Exascale designs. The results of this analytical comparison are corroborated by a comprehensive set of simulations. Altogether, they outline comparative behaviors of checkpoint strategies at very large scale, thereby providing insight that is hardly accessible to direct experimentation. Copyright © 2013 John Wiley & Sons, Ltd.     

Accelerating scientific computations with mixed precision algorithms

On modern architectures, the performance of 32-bit operations is often at least twice as fast as the performance of 64-bit operations. By using a combination of 32-bit and 64-bit floating point arithmetic, the performance of many dense and sparse linear algebra algorithms can be significantly enhanced while maintaining the 64-bit accuracy of the resulting solution. The approach presented here can apply not only to conventional processors but also to other technologies such as Field Programmable Gate Arrays (FPGA), Graphical Processing Units (GPU), and the STI Cell BE processor. Results on modern processor architectures and the STI Cell BE are presented.

Program summary

Program title: ITER-REFCatalogue identifier: AECO_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECO_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 7211No. of bytes in distributed program, including test data, etc.: 41 862Distribution format: tar.gzProgramming language: FORTRAN 77Computer: desktop, serverOperating system: Unix/LinuxRAM: 512 MbytesClassification: 4.8External routines: BLAS (optional)Nature of problem: On modern architectures, the performance of 32-bit operations is often at least twice as fast as the performance of 64-bit operations. By using a combination of 32-bit and 64-bit floating point arithmetic, the performance of many dense and sparse linear algebra algorithms can be significantly enhanced while maintaining the 64-bit accuracy of the resulting solution.Solution method: Mixed precision algorithms stem from the observation that, in many cases, a single precision solution of a problem can be refined to the point where double precision accuracy is achieved. A common approach to the solution of linear systems, either dense or sparse, is to perform the LU factorization of the coefficient matrix using Gaussian elimination. First, the coefficient matrix A is factored into the product of a lower triangular matrix L and an upper triangular matrix U. Partial row pivoting is in general used to improve numerical stability resulting in a factorization PA=LU, where P is a permutation matrix. The solution for the system is achieved by first solving Ly=Pb (forward substitution) and then solving Ux=y (backward substitution). Due to round-off errors, the computed solution, x, carries a numerical error magnified by the condition number of the coefficient matrix A. In order to improve the computed solution, an iterative process can be applied, which produces a correction to the computed solution at each iteration, which then yields the method that is commonly known as the iterative refinement algorithm. Provided that the system is not too ill-conditioned, the algorithm produces a solution correct to the working precision.Running time: seconds/minutes     

Infants' reactions to perceptual paradox during mother–infant interaction.

36 3-mo-old infants interacted with their mothers under conditions in which they could see and hear their mothers (correlated auditory plus visual information: A?+?V), see but not hear their mothers (V), and hear but not see their mothers (A); the latter 2 conditions are termed perceptual paradox. The interactions were videotaped, and the Ss' behavior was judged by naive observers who used a subjective 7-point rating scale of infant affect. For 2 groups of Ss, 3 1-min presentations of the A?+?V condition were alternated with 3 1-min presentations of either A (Group 1) or V (Group 2) conditions. In both groups, Ss were judged as being more distressed during unimodal presentations than during bimodal presentations. In a 3rd group, unimodal (A) presentations were alternated with unimodal (V) presentations. Ss in this group were significantly more distressed when they could hear but not see their mothers than when they could see but not hear their mothers. Results demonstrate the suitability of global subjective ratings of affective state in studies of infant perception. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay of gratification: Some longitudinal personality correlates.

Two brief laboratory tasks measuring delay of gratification in different ways were administered to 116 4-yr-old children. Personality data were available on these children separately at ages 3, 4, 7, and 11 yrs in the form of California Child Q-Set ratings by independent sets of teachers and examiners. The 2 delay-of-gratification measures were used to generate a more broadly based index of delay of gratification, and this index was correlated with the personality ratings available at the 4 ages. Boys who delayed gratification tended to be described as deliberative, attentive, reasonable, reserved, cooperative, and able to modulate motivational and emotional impulse. Boys who did not delay gratification, by contrast, were irritable, restless, aggressive, and generally not self-controlled. Girls who delayed gratification were consistently described as intelligent, resourceful, and competent. Girls who did not delay tended to go to pieces under stress; to be victimized by other children; and to be easily offended, sulky, and whiny. Findings are interpreted in terms of the constructs of ego control and ego resiliency and the differential socialization of the sexes. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychologists in defense of the Federal Trade Commission.

The professional and economic challenges to psychologists posed by organized medicine have been stymied in the past by the Federal Trade Commission and by strict enforcement of the antitrust laws. Now that professionals' competition and consumer choice are being supported in the courts, the American Medical Association (AMA) is redoubling its efforts to retain a monopolistic hold on health care, hospital practice, and health insurance throughout the nation. Organized psychology, with the help of other professions and the Congress, has barely held the line against politically and economically stronger forces. The Association for the Advancement of Psychology and the American Psychological Association actively opposed the AMA's proposed legislation in 1981 and 1982 that would have allowed the AMA to circumvent valid law. The medical profession has actively worked to control all health care and deny psychologists hospital staff privileges, preventing group practice between physicians and psychologists, denying them health insurance reimbursement, and restricting psychological services to physician supervision. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MULTIMEDIA NETWORKING A Leading-Edge Communication Technology

The realization of digital multimedia's full business potential requires networking. This article discusses the value-added benefits to the corporation of networked multimedia as well as the choice of architectures and technologies needed to deliver multimedia networking solutions.