Multi-objective improvement of software using co-evolution and smart seeding

Optimising non-functional properties of software is an important part of the implementation process. One such property is execution time, and compilers target a reduction in execution time using a variety of optimisation techniques. Compiler optimisation is not always able to produce semantically equivalent alternatives that improve execution times, even if such alternatives are known to exist. Often, this is due to the local nature of such optimisations. In this paper we present a novel framework for optimising existing software using a hybrid of evolutionary optimisation techniques. Given as input the implementation of a program or function, we use Genetic Programming to evolve a new semantically equivalent version, optimised to reduce execution time subject to a given probability distribution of inputs. We employ a co-evolved population of test cases to encourage the preservation of the program’s semantics, and exploit the original program through seeding of the population in order to focus the search. We carry out experiments to identify the important factors in maximising efficiency gains. Although in this work we have optimised execution time, other non-functional criteria could be optimised in a similar manner

Few-nucleon systems in translationally invariant harmonic oscillator basis

We present a translationally invariant formulation of the no-core shell model approach for few-nucleon systems. We discuss a general method of antisymmetrization of the harmonic-oscillator basis depending on Jacobi coordinates. The use of a translationally invariant basis allows us to employ larger model spaces than in traditional shell-model calculations. Moreover, in addition to two-body effective interactions, three- or higher-body effective interactions as well as real three-body interactions can be utilized. In the present study we apply the formalism to solve three and four nucleon systems interacting by the CD-Bonn nucleon-nucleon potential. Results of ground-state as well as excited-state energies, rms radii and magnetic moments are discussed. In addition, we compare charge form factor results obtained using the CD-Bonn and Argonne V8' NN potentials.Comment: 25 pages. RevTex. 13 Postscript figure

Reaction mechanism and characteristics of T_{20} in d + ^3He backward elastic scattering at intermediate energies

For backward elastic scattering of deuterons by ^3He, cross sections \sigma and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are analyzed by the PWIA and by the general formula which includes virtual excitations of other channels, with the assumption of the proton transfer from ^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev equation, the PWIA describes global features of the experimental data, while the virtual excitation effects are important for quantitative fits to the T_{20} data. Theoretical predictions on T_{20}, K_y^y (polarization transfer coefficient) and C_{yy} (spin correlation coefficient) are provided up to GeV energies.Comment: REVTEX+epsfig, 17 pages including 6 eps figs, to be published in Phys. Rev.

Solutions of the Faddeev-Yakubovsky equations for the four nucleons scattering states

The Faddeev-Yakubowsky equations in configuration space have been solved for the four nucleon system. The results with an S-wave interaction model in the isospin approximation are presented. They concern the bound and scattering states below the first three-body threshold. The elastic phase-shifts for the N+NNN reaction in different ($S,T$) channels are given and the corresponding low energy expansions are discussed. Particular attention is payed to the n+t elastic cross section. Its resonant structure is well described in terms of a simple NN interaction. First results concerning the S-matrix for the coupled N+NNN-NN+NN channels and the strong deuteron-deuteron scattering length are obtained.Comment: latex.tar.gz, 36 pages, 10 figures, 11 tables. To be published in Physical Review

The Ay Problem for p-3He Elastic Scattering

We present evidence that numerically accurate quantum calculations employing modern internucleon forces do not reproduce the proton analyzing power, A_y, for p-3He elastic scattering at low energies. These calculations underpredict new measured analyzing powers by approximately 30% at E_{c.m.} = 1.20 MeV and by 40% at E_{c.m.} = 1.69 MeV, an effect analogous to a well-known problem in p-d and n-d scattering. The calculations are performed using the complex Kohn variational principle and the (correlated) Hyperspherical Harmonics technique with full treatment of the Coulomb force. The inclusion of the three-nucleon interaction does not improve the agreement with the experimental data.Comment: Latex file, 4 pages, 2 figures, to be published on Phys. Rev. Let

Adaptive Document Maps

Abstract. As document map creation algorithms like WebSOM are computationally expensive, and hardly reconstructible even from the same set of documents, new methodology is urgently needed to allow to construct document maps to handle streams of new documents entering document collection. This challenge is dealt with within this paper. In a multi-stage process, incrementality of a document map is warranted. 1 . The architecture of the experimental system allows for comparative evaluation of different constituent technologies for various stages of the process. The quality of the map generation process has been investigated based on a number of clustering and classification measures. Some conclusions concerning the impact of incremental, topic-sensitive approach on map quality are presented

Structure of boson systems beyond the mean-field

We investigate systems of identical bosons with the focus on two-body correlations. We use the hyperspherical adiabatic method and a decomposition of the wave function in two-body amplitudes. An analytic parametrization is used for the adiabatic effective radial potential. We discuss the structure of a condensate for arbitrary scattering length. Stability and time scales for various decay processes are estimated. The previously predicted Efimov-like states are found to be very narrow. We discuss the validity conditions and formal connections between the zero- and finite-range mean-field approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the present method. We compare numerical results from present work with mean-field calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with modified figures and discussion

First events from the CNGS neutrino beam detected in the OPERA experiment

The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode, through the study of nu_mu to nu_tau oscillations. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. In August 2006 a first run with CNGS neutrinos was successfully conducted. A first sample of neutrino events was collected, statistically consistent with the integrated beam intensity. After a brief description of the beam and of the various sub-detectors, we report on the achievement of this milestone, presenting the first data and some analysis results.Comment: Submitted to the New Journal of Physic