CADNA_C: A version of CADNA for use with C or C++ programs

The CADNA library enables one to estimate round-off error propagation using a probabilistic approach. The CADNA_C version enables this estimation in C or C++ programs, while the previous version had been developed for Fortran programs. The CADNA_C version has the same features as the previous one: with CADNA the numerical quality of any simulation program can be controlled. Furthermore by detecting all the instabilities which may occur at run time, a numerical debugging of the user code can be performed. CADNA provides new numerical types on which round-off errors can be estimated. Slight modifications are required to control a code with CADNA, mainly changes in variable declarations, input and output.

New version program summary

Program title: CADNA_CCatalogue identifier: AEGQ_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGQ_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.: 60 075No. of bytes in distributed program, including test data, etc.: 710 781Distribution format: tar.gzProgramming language: C++Computer: PC running LINUX with an i686 or an ia64 processor, UNIX workstations including SUN, IBMOperating system: LINUX, UNIXClassification: 6.5Catalogue identifier of previous version: AEAT_v1_0Journal reference of previous version: Comput. Phys. Comm. 178 (2008) 933Does the new version supersede the previous version?: NoNature of problem: A simulation program which uses floating-point arithmetic generates round-off errors, due to the rounding performed at each assignment and at each arithmetic operation. Round-off error propagation may invalidate the result of a program. The CADNA library enables one to estimate round-off error propagation in any simulation program and to detect all numerical instabilities that may occur at run time.Solution method: The CADNA library [1-3] implements Discrete Stochastic Arithmetic [4,5] which is based on a probabilistic model of round-off errors. The program is run several times with a random rounding mode generating different results each time. From this set of results, CADNA estimates the number of exact significant digits in the result that would have been computed with standard floating-point arithmetic.Reasons for new version: The previous version (AEAT_v1_0) enables the estimation of round-off error propagation in Fortran programs [2]. The new version has been developed to enable this estimation in C or C++ programs.Summary of revisions: The CADNA_C source code consists of one assembly language file (cadna_rounding.s) and twenty-three C++ language files (including three header files). cadna_rounding.s is a symbolic link to the assembly file corresponding to the processor and the C++ compiler used. This assembly file contains routines which are frequently called in the CADNA_C C++ files to change the rounding mode. The C++ language files contain the definition of the stochastic types on which the control of accuracy can be performed, CADNA_C specific functions (for instance to enable or disable the detection of numerical instabilities), the definition of arithmetic and relational operators which are overloaded for stochastic variables and the definition of mathematical functions which can be used with stochastic arguments. As a remark, on 64-bit processors, the mathematical library associated with the GNU C++ compiler may provide incorrect results or generate severe bugs with rounding towards −∞ and +∞, which the random rounding mode is based on. Therefore, if CADNA_C is used on a 64-bit processor with the GNU C++ compiler, mathematical functions are computed with rounding to the nearest, otherwise they are computed with the random rounding mode. It must be pointed out that the knowledge of the accuracy of the argument of a mathematical function is never lost.Additional comments: In the library archive, users are advised to read the INSTALL file first. The doc directory contains a user guide named ug.cadna.pdf and a reference guide named, ref_cadna.pdf. The user guide shows how to control the numerical accuracy of a program using CADNA, provides installation instructions and describes test runs.The reference guide briefly describes each function of the library. The source code (which consists of C++ and assembly files) is located in the src directory. The examples directory contains seven test runs which illustrate the use of the CADNA library and the benefits of Discrete Stochastic Arithmetic.Running time: The version of a code which uses CADNA runs at least three times slower than its floating-point version. This cost depends on the computer architecture and can be higher if the detection of numerical instabilities is enabled. In this case, the cost may be related to the number of instabilities detected.References:

[1]

The CADNA library, URL address: http://www.lip6.fr/cadna.

[2]

F. Jézéquel, J.-M. Chesneaux, CADNA: a library for estimating round-off error propagation, Comput. Phys. Comm. 178 (12) (2008) 933-955.

[3]

N.S. Scott, F. Jézéquel, C. Denis, J.-M. Chesneaux, Numerical ‘health check’ for scientific codes: the CADNA approach, Comput. Phys. Comm. 176 (8) (2007) 507-521.

[4]

J. Vignes, A stochastic arithmetic for reliable scientific computation, Math. Comput. Simulation 35 (1993) 233-261.

[5]

J. Vignes, Discrete stochastic arithmetic for validating results of numerical software, Numer. Algorithms 37 (2004) 377-390.

     

Bag of soft biometrics for person identification

In this work we seek to provide insight on the general topic of soft biometrics. We firstly present a new refined definition of soft biometrics, emphasizing on the aspect of human compliance, and then proceed to identify candidate traits that accept this novel definition. We then address relations between traits and discuss associated benefits and limitations of these traits. We also consider two novel soft biometric traits, namely weight and color of clothes and we analyze their reliability. Related promising results on the performance are provided. Finally, we consider a new application, namely human identification solely carried out by a bag of facial, body and accessory soft biometric traits, and as an evidence of its practicality, we provide preliminary promising results.     

Formal object-oriented development of a voting system test oracle

We report on the formal development of a test oracle for an electronic-voting system, detailing our approach which was based on a lightweight integration of Event-B, UML, and Java. This lightweight integration focuses on a coherent development process rather than on formal integration at the model/language level. We then briefly review alternative development approaches involving the use of JML and OCL. We conclude that the use of the OCL would offer few benefits, if any, in our formal development process.     

Spectral response of benthic diatoms with different sediment backgrounds

Remote sensing of terrestrial vegetation uses a wide range of vegetation indices (VIs) to monitor plant characteristics, but these indices can be very sensitive to canopy background reflectance. This study investigated background influences on VIs applied to intertidal microphytobenthos, using a synthetic spectral library constituted by a spectral combination of three contrasting types of sediment (sand, fine sand, and mud) and reflectance spectra of benthic diatom monospecific cultures obtained in controlled conditions. The spectral database exhibited, for the same biomass range (3-182 mg chlorophyll a m^− 2), marked differences in albedo and spectral contrast linked to sediment variability in water content, grain size, and organic matter content. Several VIs were evaluated, from ratios using visible and near infrared wavelengths, to hyperspectral indices (derivative analysis, continuum removal). Among the ratios, the Normalized Difference Vegetation Index (NDVI) appeared less sensitive to background effects than VIs with soil corrections such as the Perpendicular Vegetation Index (PVI), the Soil-Adjusted Vegetation Index (SAVI), the Modified second Soil-Adjusted Vegetation Index (MSAVI2) or the Transformed Soil-Adjusted Vegetation Index (TSAVI). The lower efficacy of soil-corrected VIs may be explained by the structural differences and optical behavior of soil vs. canopies compared to sediment vs. microphytobenthos biofilms. The background effects were minimized using Modified Gaussian Model indices at 632 nm and 675 nm, and the second derivative at 632 nm, while poor results were obtained with the red-edge inflection point (REIP) and the second derivative at 675 nm. The least sensitive index was the Phytobenthos Index which is very similar to the NDVI, but uses a red wavelength at 632 nm instead of 675 nm, to account for the absorption by chlorophyll c. The modified NDVI₇₀₅, where the 705 nm wavelength replaces the red band, showed moderate background sensitivity. Moreover, the NDVI₇₀₅ and the Phytobenthos Index have the additional relevant property of being less sensitive to the index saturation response with increasing biomass. Unfortunately, these VIs cannot be applied to broad-band multispectral satellite images, and require sensors with a hyperspectral resolution. Nevertheless, this study showed that the background influence was not a limitation to applying the ubiquitous NDVI to map intertidal microphytobenthos using multispectral satellite images.     

Basic and clinical proteomics from the EU Health Research perspective

The European Union (EU) is one of the main public funders of research in Europe and its major instrument for funding is the Seventh Framework Programme for research and technological development (FP7). The bulk of funding in FP7 goes to collaborative research, with the objective of establishing excellent research projects and networks. Understanding the functions of proteins is essential for the rational development of disease prevention, diagnosis and treatment, therefore the EU has largely invested in proteomics, in particular for technology development, data standardisation and sharing efforts, and the application of proteomics in the clinic. The scientific community, including both academia and industry, is encouraged to apply for FP7 funding so that the EU can even more efficiently support innovative health research and ultimately, bring better healthcare to patients.     

A low-complexity microprocessor design with speculative pre-execution

Current superscalar architectures strongly depend on an instruction issue queue to achieve multiple instruction issue and out-of-order execution. However, the issue queue requires a centralized structure and mainly causes globally broadcasting operations to wakeup and select the instructions. Therefore, a large issue queue ultimately results in a low clock rate along with a high circuit complexity. In other words, the increasing demands for a larger issue queue correspondingly impose a significant burden on achieving a higher clock speed.This paper discusses our Speculative Pre-Execution Assisted by compileR (SPEAR), a low-complexity issue queue design. SPEAR is designed to manage the small window superscalar architecture more efficiently without increasing the window size. To this end, we have first recognized that the long memory latency is one of the factors that demand a large window, and we aim at achieving early execution of the miss-causing load instructions using another hierarchy of an issue queue. We pre-execute those miss-causing instructions speculatively as an additional prefetching thread. Simulation results show that the SPEAR design achieves performance comparable to or even better than what would be obtained in superscalar architectures with a large issue queue. However, SPEAR is designed with smaller issue queues which consequently can be implemented with low hardware complexity and high clock speed.     

Role of plant volatiles in the search for a host by parasitoidDiglyphus isaea (Hymenoptera: Eulophidae)

Diglyphus isaea Walker is a larval ectoparasitoid used in biological pest control against the American serpentine leaf minerLiriomyza trifolii Burgess. We studied the parasitoid's host searching behavior, using olfactometric methods. Our data show that the parasitoids locate host larvae (a leafmining dipteran) on the basis of volatile signals released by the plant-host complex. FemaleD. isaea are strongly attracted to the odors arising from damaged bean plants, whereas they show practically no response to intact plants. The results of our chemical analyses showed that about 15 components were present, two of which,cis-3-hexen-1-ol and 4-hydroxy-4-methyl-2-pentanone, were present in significantly larger quantities in the leaf extracts from mined or damaged bean plants than in those from healthy plants. The damage inflicted by the host larvae on these plants triggers the release of larger amounts of these substances, which probably lead the parasites to their hosts. The compounds thus act as synomones.     

Quasi-steady formation of bubbles and drops viewed as processes that break bifurcation

Instabilities occurring during the quasi-steady formation of bubbles and drops at a circular orifice through a thin plate, which separates a cylindrical upper vessel of quiescent liquid from a lower air chamber maintained at constant pressure, are considered in connection with the Rayleigh-Taylor instability of a flat meniscus. The control parameters of the problem are the Eötvös number Eö, and the excess-pressure number Δ, which characterizes the pressure difference between gas and liquid across the orifice. The Rayleigh-Taylor case i.e., Δ = 0, can be viewed as a perfect bifurcating problem. A subcritical bifurcation emerges from the critical point, Eö_c = 5 B783186, beyond which the flat meniscus is unstable for axisymmetric perturbations. Bubbles (Δ > 0), and drops (Δ < 0) appear as solutions that break bifurcation. When an appropriate measure of their magnitude ε is introduced, it can be shown analytically that the equilibrium surface at the critical point is a cusp; its intermediate sheet is stable, while its two upper and lower sheets are unstable. The analytical bifurcation set onto the control parameters plane is valid only around the critical point.     

Analyse des réseaux faiblement non linéaires par les développements en série de Volterra. Application aux montages a transistors bipolaires

The interest of using Volterra series for the analysis of weakly nonlinear circuits has been largely evoked in previous papers. The present paper shows how to use these series for a systematic analysis of most nonlinear circuits, thus allowing fast processing with computers. The computer implementation of this method allows fast evaluation of distorsion in bipolar transistor circuits.     

The pressure effect on the wax formation in diesel fuel☆

The prevention of wax formation under high pressure on new diesel engine requires a good understanding of the behaviour of the paraffin molecules crystallization. In this work a diesel from a Petrogal refinery was investigated under pressure. In particular the melting curve was measured from atmospheric pressure to 100 MPa by an optical technique. The behaviour of the solid phase with the pressure was also investigated up to 50 MPa by filtration. The results obtained show an increase in the diesel cloud point of about 25 °C at the operating pressure of a common rail engine. It is clear from our results that the increase of the diesel cloud point must be taken into account in the development of new diesel engines where the diesel is injected under high pressure.All the results obtained were successfully predicted with a thermodynamic model able to describe multiphase equilibrium.