Laboratorio virtual de matemáticas (ALME2005)

Concebimos que la modelación de fenómenos es una práctica que está ligada a la construcción de conocimientos matemáticos y en este sentido se han realizado investigaciones entorno a su incorporación al contexto escolar. Sin embargo, el incorporar la experimentación en el aula de matemáticas conlleva dificultades, una de ellas es la carencia de material de laboratorio. El laboratorio virtual es un proyecto que intenta suplir la ausencia de un laboratorio físicamente, sin embargo, esta sustitución desencadena diferentes relaciones entre los actores. En este trabajo se pretende mostrar como es que un laboratorio simulado, podría contribuir a la incorporación a sistemas escolares concretos de diseños de aprendizaje basados en las prácticas sociales de modelación. Se da evidencia de cómo se desarrollan acciones e interacciones colaborativas alrededor del laboratorio virtual.

Automatic parallel code generation for message passing on distributed memory systems

The availability of a very accurate dependence graph for a scalar code is the basis for the automatic generation of an efficient parallel implementation. The strategy for this task which is encapsulated in a comprehensive data partitioning code generation algorithm is described. This algorithm involves the data partition, calculation of assignment ranges for partitioned arrays, addition of a comprehensive set of execution control masks, altering loop limits, addition and optimisation of communications for all data. In this context, the development and implementation of strategies to merge communications wherever possible has proved an important feature in producing efficient parallel implementations for numerical mesh based codes. The code generation strategies described here are embedded within the Computer Aided Parallelisation tools (CAPTools) software as a key part of a toolkit for automating as much as possible of the parallelisation process for mesh based numerical codes. The algorithms used enables parallelisation of real computational mechanics codes with only minor user interaction and without any prior manual customisation of the serial code to suit the parallelisation tool.

Integrating user knowledge with information from parallelisation tools to facilitate the automatic generation of efficient parallel FORTRAN code

User supplied knowledge and interaction is a vital component of a toolkit for producing high quality parallel implementations of scalar FORTRAN numerical code. In this paper we consider the necessary components that such a parallelisation toolkit should possess to provide an effective environment to identify, extract and embed user relevant user knowledge. We also examine to what extent these facilities are available in leading parallelisation tools; in particular we discuss how these issues have been addressed in the development of the user interface of the Computer Aided Parallelisation Tools (CAPTools). The CAPTools environment has been designed to enable user exploration, interaction and insertion of user knowledge to facilitate the automatic generation of very efficient parallel code. A key issue in the user's interaction is control of the volume of information so that the user is focused on only that which is needed. User control over the level and extent of information revealed at any phase is supplied using a wide variety of filters. Another issue is the way in which information is communicated. Dependence analysis and its resulting graphs involve a lot of sophisticated rather abstract concepts unlikely to be familiar to most users of parallelising tools. As such, considerable effort has been made to communicate with the user in terms that they will understand. These features, amongst others, and their use in the parallelisation process are described and their effectiveness discussed.

Automatic code generation of overlapped communications in a parallelisation tool

This paper addresses the exploitation of overlapping communication with calculation within parallel FORTRAN 77 codes for computational fluid dynamics (CFD) and computational structured dynamics (CSD). The obvious objective is to overlap interprocessor communication with calculation on each processor in a distributed memory parallel system and so improve the efficiency of the parallel implementation. A general strategy for converting synchronous to overlapped communication is presented together with tools to enable its automatic implementation in FORTRAN 77 codes. This strategy is then implemented within the parallelisation toolkit, CAPTools, to facilitate the automatic generation of parallel code with overlapped communications. The success of these tools are demonstrated on two codes from the NAS-PAR and PERFECT benchmark suites. In each case, the tools produce parallel code with overlapped communications which is as good as that which could be generated manually. The parallel performance of the codes also improve in line with expectation.

Automatic and effective multi-dimensional parallelisation of structured mesh based codes

The most common parallelisation strategy for many Computational Mechanics (CM) (typified by Computational Fluid Dynamics (CFD) applications) which use structured meshes, involves a 1D partition based upon slabs of cells. However, many CFD codes employ pipeline operations in their solution procedure. For parallelised versions of such codes to scale well they must employ two (or more) dimensional partitions. This paper describes an algorithmic approach to the multi-dimensional mesh partitioning in code parallelisation, its implementation in a toolkit for almost automatically transforming scalar codes to parallel form, and its testing on a range of ‘real-world’ FORTRAN codes. The concept of multi-dimensional partitioning is straightforward, but non-trivial to represent as a sufficiently generic algorithm so that it can be embedded in a code transformation tool. The results of the tests on fine real-world codes demonstrate clear improvements in parallel performance and scalability (over a 1D partition). This is matched by a huge reduction in the time required to develop the parallel versions when hand coded – from weeks/months down to hours/days.

Virtual manufacturing and design in the real world - implementation and scalability on HPPC systems

Virtual manufacturing and design assessment increasingly involve the simulation of interacting phenomena, sic. multi-physics, an activity which is very computationally intensive. This chapter describes an attempt to address the parallel issues associated with a multi-physics simulation approach based upon a range of compatible procedures operating on one mesh using a single database - the distinct physics solvers can operate separately or coupled on sub-domains of the whole geometric space. Moreover, the finite volume unstructured mesh solvers use different discretization schemes (and, particularly, different ‘nodal’ locations and control volumes). A two-level approach to the parallelization of this simulation software is described: the code is restructured into parallel form on the basis of the mesh partitioning alone, that is, without regard to the physics. However, at run time, the mesh is partitioned to achieve a load balance, by considering the load per node/element across the whole domain. The latter of course is determined by the problem specific physics at a particular location.

The specification and design of an interactive virtual environment for use in teacher training

The original concept was to create a 'simulation' which would provide trainee teachers, specializing in Information and Communications Technology (ICT) with the opportunity to explore a primary school environment. Within the simulation, factors affecting the development and implementation of ICT would be modelled so that trainees would be able to develop the skills, knowledge and understanding necessary to identify appropriate strategies to overcome the limitations. To this end, we have developed Allsorts Primary - the prototype of a simulated interactive environment, representing a typical primary school

Exploiting virtual prototyping for reliability assessment

Products manufactured by the electronics sector are having a major impact in telecommunications, transportation space applications, biomedical applications, consumer products, intelligent hand held devices, and of course,the computer. Demands from end-users in terms of greater product functionality, adoption of environmentally friendly materials, and further miniaturization continually pose several challenges to electronics companies. In the context of electronic product design and manufacture, virtual prototying software tools are allowing companies to dramatically reduce the number of phsysical prototypes and design iterations required in product development and hence reduce costs and time to market. This paper details of the trends in these technolgies and provides an example of their use for flip-chip assembly technology.

The semi-automatic parallelisation of scientific application codes using a computer aided parallelisation toolkit

The shared-memory programming model can be an effective way to achieve parallelism on shared memory parallel computers. Historically however, the lack of a programming standard using directives and the limited scalability have affected its take-up. Recent advances in hardware and software technologies have resulted in improvements to both the performance of parallel programs with compiler directives and the issue of portability with the introduction of OpenMP. In this study, the Computer Aided Parallelisation Toolkit has been extended to automatically generate OpenMP-based parallel programs with nominal user assistance. We categorize the different loop types and show how efficient directives can be placed using the toolkit's in-depth interprocedural analysis. Examples are taken from the NAS parallel benchmarks and a number of real-world application codes. This demonstrates the great potential of using the toolkit to quickly parallelise serial programs as well as the good performance achievable on up to 300 processors for hybrid message passing-directive parallelisations.

Automatic relative debugging of OpenMP programs

In this work we show how automatic relative debugging can be used to find differences in computation between a correct serial program and an OpenMP parallel version of that program that does not yield correct results. Backtracking and re-execution are used to determine the first OpenMP parallel region that produces a difference in computation that may lead to an incorrect value the user has indicated. Our approach also lends itself to finding differences between parallel computations, where executing with M threads produces expected results but an N thread execution does not (M, N > 1, M ≠ N). OpenMP programs created using a parallelization tool are addressed by utilizing static analysis and directive information from the tool. Hand-parallelized programs, where OpenMP directives are inserted by the user, are addressed by performing data dependence and directive analysis.

Powering the virtual university with standard portal technology

This article describes ongoing research on developing a portal framework based on the OASIS Web Services for Remote Portlets (WSRP) standard for integration of Web-based education contents and services made available through a model for a European Networked University. We first identify the requirements for such a framework that supports integration at the presentation level and collaboration in developing and updating study programmes and course materials. We then outline the architecture design, and report on the initial implementation and preliminary evaluation.

Virtual assignments: breach of covenant against parting with or sharing of possession

Comments on the Chancery Division decision in Clarence House Ltd v National Westminster Bank Plc on whether the alienation covenant in a lease of commercial premises had been breached by the tenant effecting a virtual assignment of it, under which all the economic benefits and burdens of the lease were transferred to a third party without there being any actually assignment of the leasehold interest or change in occupancy.

Delivering processing instruction in classroom and virtual contexts

Processing Instruction (PI) is an approach to grammar instruction for second language learning. It derives its name from the fact that the instruction (both the explicit explanation as well as the practices) attempt to influence, alter, and/or improve the way learners process input. PI contrasts with traditional grammar instruction in many ways, most principally in its focus on input whereas traditional grammar instruction focuses on learners' output. The greatest contribution of PI to both theory and practice is the concept of "structured input", a form of comprehensible input that has been manipulated to maximize learners' benefit of exposure to input. This volume focuses on a new issue for PI, the role of technology in language learning. It examines empirically the differential effects of delivering PI in classrooms with an instructor and students interacting (with each other and with the instructor) versus on computers to students working individually. It also contributes to the growing body of research on the effects of PI on different languages as well as different linguistic items: preterite/imperfect aspectual contrast and negative informal commands in Spanish, the subjunctive of doubt and opinion in Italian, and the subjunctive of doubt in French. Further research contributions are made by comparing PI with other types of instruction, specifically, with meaning-oriented output instruction.