Anthony J. G. Hey

Matrix algorithms on a hypercube I: Matrix multiplication☆

Abstract We discuss algorithms for matrix multiplication on a concurrent processor containing a two-dimensional mesh or richer topology. We present detailed performance measurements on hypercubes with 4, 16, and 64 nodes, and analyze them in terms of communication overhead and load balancing. We show that the decomposition into square subblocks is optimal C code implementing the algorithms is available.

SU(6) w and Decays of Baryon Resonances

Abstract The decay rates of baryon resonances assigned to the {70, 1 − } and {56, 2 + } presentations of SU(6) W ⊗ O(3) are subjected to a detailed comparison with an SU(6) W model motivated by the recent work of Melosh. We conclude that SU(6) W is remarkably successful as an approximate symmetry for decay vertices.

A Proposal for a User-Level, Message-Passing Interface in a Distributed Memory Environment

This paper describes Message Passing Interface 1 (MPI1), a proposed library interface standard for supporting point-to-point message passing. The intended standard will be provided with Fortran 77 and C interfaces, and will form the basis of a standard high level communication environment featuring collective communication and data distribution transformations. The standard proposed here provides blocking and nonblocking message passing between pairs of processes, with message selectivity by source process and message type. Provision is made for noncontiguous messages. Context control provides a convenient means of avoiding message selectivity conflicts between different phases of an application. The ability to form and manipulate process groups permit task parallelism to be exploited, and is a useful abstraction in controlling certain types of collective communication.

Feynman and computation: exploring the limits of computers

Feynmans Course On Computation Feynman and Computation (John J. Hopfield) Neural Networks and Physical Systems with Emergent Collective Computational Abilities (John J. Hopfield) Feynman as a Colleague (Carver A. Mead) Collective Electrodynamics I (Carver A. Mead) A Memory (Gerald Jay Sussman) Numerical Evidence That the Motion of Pluto Is Chaotic (Gerald Jay Sussman and Jack Wisdom) Reducing The Size Theres Plenty of Room at the Bottom (Richard P. Feynman) Information Is Inevitably Physical (Rolf Landauer) Scaling of MOS Technology to Submicrometer Feature Sizes (Carver A. Mead) Richard Feynman and Cellular Vacuum (Marvin Minsky) Quantum Limits Simulating Physics with Computers (Richard P. Feynman) Quantum Robots (Paul Benioff) Quantum Information Theory (Charles H. Bennett) Quantum Computation (Richard J. Hughes) Parallel Computation Computing Machines in the Future (Richard P. Feynman) Internetics: Technologies, Applications, and Academic Fields (Geoffrey C. Fox) Richard Feynman and the Connection Machine (W. Daniel Hillis) Crystalline Computation (Norman H. Margolus) Fundamentals Information, Physics, Quantum: The Search for Links (John Archibald Wheeler) Feynman, Barton and the Reversible Schrdinger Difference Equation (Ed Fredkin) Action, or the Fungibility of Computation (Tommaso Toffoli) Algorithmic Randomness, Physical Entropy, Measurements, and the Demon of Choice (Wojciech Zurek).

Experiments in MIMD parallelism

The paper reviews the problems inhibiting the widespread use of parallel processing by both industry and by software houses. The two key issues of portability of code and of generality of parallel architectures are discussed. An overview of useful computational models and programming paradigms for parallel machines is presented along with some detailed case studies implemented on transputer arrays. Valiants results on optimally universal parallel machines are reviewed along with the prospects of building truly general-purpose parallel computers. Some remarks on language and software tool developments for parallel programming form the conclusion to the paper.

Quarks and the helicity structure of photoproduction amplitudes

Abstract Algebraic properties of the transformation between constituent and current quarks are used to derive the helicity structure of photoproduction matrix elements.

The Fourth Paradigm: Data-Intensive Scientific Discovery [Point of View]

We are now seeing governments and funding agencies looking at ways to increase the value and pace of scientific research through increased or open access to both data and publications. In this point of view article, we wish to look at another aspect of these twin revolutions, namely, how to enable developers, designers and researchers to build intuitive,multimodal, user-centric, scientific applications that can aid and enable scientific research.

String tensions for lattice gauge theories in 2 + 1 dimensions☆

Abstract Compact U(1) and SU(2) lattice gauge theories in 3 euclidean dimensions are studied by standard Monte Carlo techniques. The question of extracting reliable string tensions from these theories is examined in detail, including a comparison of the Monte Carlo Wilson loop data with weak coupling predictions and a careful error analysis: our conclusions are rather different from those of previous investigations of these theories. In the case of U(1) theory, we find that only a tiny range of β values can possibly be relevant for extracting a string tension and we are unable to convincingly demonstrate the expected exponential dependence of the string tension on β. For the SU(2) theory we are able to determine, albeit with rather large errors, a string tension from a study of Wilson loops.

THE QUANTUM UNIVERSE

Preface Prologue Route map 1. Waves versus particles 2. Heisenberg and uncertainty 3. Schrodinger and matter waves 4. Atoms and nuclei 5. Quantum tunnelling 6. Pauli and the elements 7. Death of a star 8. Quantum co-operation and superfluids 9. Feynman rules 10. Weak photons and strong glue Appendices Epilogue Glossary Suggestions for further reading Photo-credits Subject index Names index.

Practical Parallelism using Transputer Arrays

This paper explores methods for extracting parallelism from a wide variety of numerical applications. We investigate communications overheads and load-balancing for networks of transputers. After a discussion of some practical strategies for constructing occam programs, two case studies are analysed in detail.