Davide Guerri

Two Layers Distributed Shared Memory

This paper presents a methodology to design a distributed shared memory by decomposing it into two layers. An application independent layer supplies the basic functionalities to access shared structures and optimizes these functionalities according to the underlying architecture. On top of this layer, that can be seen as an application independent run time support, an application dependent layer defines the most suitable consistency model for the considered class of applications and it implements the most appropriate caching and prefetching strategies for the consistency model. To exemplify this methodology, we introduce DVSA, a package that implements the application independent layer and SHOB, an example of the second layer. SHOB defines a release consistency model for iterative numerical algorithms and it implements the corresponding caching and prefetching strategies. We present some experimental results of the methodology and discuss the performance of a uniform multigrid method developed through SHOB on a massively parallel architecture, the Meiko CS2, and on a cluster of workstations.

Automation and intelligent scheduling of distributed system functional testing

This paper presents the approach to functional test automation of services (black-box testing) and service architectures (grey-box testing) that has been developed within the MIDAS project and is accessible on the MIDAS SaaS. In particular, the algorithms and techniques adopted for addressing input and oracle generation, dynamic scheduling, and session planning issues supporting service functional test automation are illustrated. More specifically, the paper details: (i) the test input generation based on formal methods and temporal logic specifications, (ii) the test oracle generation based on service formal specifications, (iii) the dynamic scheduling of test cases based on probabilistic graphical reasoning, and (iv) the reactive, evidence-based planning of test sessions with on-the-fly generation of new test cases. Finally, the utilisation of the MIDAS prototype for the functional test of operational services and service architectures in the healthcare industry is reported and assessed. A planned evolution of the technology deals with the testing and troubleshooting of distributed systems that integrate connected objects.

Prototypal ambient intelligence framework for assessment of food quality and safety

The holistic view of Ambient Intelligence proposed by the European IST Committee [1] suggests to start with the creation of an Ambient Intelligence (AmI) landscape for seamless delivery of services and applications [14,6]. In this paper we show the efforts that have been made to realize the AmI vision in a very challenging test bed such as the fine grained, continuous quality monitoring and traceability across entire food-chains. We employed our ideas in the framework of the GoodFood Integrate Project (FP6-IST-1-508774-IP) [3] which aims at developing a new generation of analytical methods based on Micro and Nano Technology solutions for safety and quality assurance along the food chain in the agrofood industry. The project proposes an AmI GRID vision that involves Remote Data Acquisition (RDA) for gathering information over a sensed environment, a communication infrastructure transporting data across the actors of the framework and a software component (AmI Core) represented by a set of systems involved in storage, monitoring, intelligent analysis and presentation of the data. We concentrated on both the infrastructure and the AmI Core. Regarding the infrastructure, we worked on the definition of a protocol for interconnecting the “Ambient hemisphere” of AmI (RDA) with the “Intelligence hemisphere” (AmI Core) and we developed a highly scalable, loosely coupled and bus-based interconnection scheme for the AmI Core. The AmI Core has been then populated with software entities (AmIDevices), in charge of the storage, monitoring, intelligent analysis and presentation of data. Fundamental results have been obtained in the definition and development of seamless integrating components designed for the abstraction, automatic composition, interaction between the Ambient and the Intelligence, user-friendly human interaction, computational efficiency, scalability and evolution. These results will guarantee the integration int the AmI framework of computer aided Decision Support Systems designed as a management tool to assist the domain experts in the different food-chains to achieve their target levels of efficiency, quality and risk management.

Evaluation of a virtual shared memory machine by the compilation of data parallel loops

We introduce DVSA, distributed virtual shared areas, a virtual machine supporting the sharing of information on distributed memory architectures. The shared memory is structured as a set of areas where the size of each area may be chosen in all architecture dependent range. DVSA supports the sharing of areas rather than of variables because the exchange of chunks of data may result in better performances on distributed memory architectures offering little or no hardware support to information sharing. DVSA does not implement replication or prefetching strategies under the assumption that these strategies should be implemented by application specific virtual machines. The definition of these machines may often be driven by the compilation of the adopted programming languages. To validate the assumption, at first we consider the implementation of data parallel loops and show that a set of static analyses based on the closed forms approach makes it possible to define compiler driven caching and prefetching strategies. These strategies fully exploit the operations offered by the DVSA machine and they noticeably reduce the time to access shared information. The optimizations strategies that can be exploited by the compiler includes the merging of accesses to avoid multiple access to the same area, the prefetching of areas and the reduction of the overhead due to barrier synchronization. Preliminary performance figures are discussed.

DVSA and SHOE: support to shared data structures on distributed memory architectures

With reference to numerical iterative algorithms, this paper exemplifies a methodology to design the runtime support of applications sharing a set of data structures on a distributed memory architecture. According to the methodology, the support is decomposed into two layers: an application independent one, supplying the basic functionalities to access a shared structure, and an application dependent layer that implements the caching and prefetching strategies most appropriate for the considered application. Starting from this assumption, we introduce DVSA, a package that implements the application independent layer and SHOB, one of the packages that can be developed on top of DVSA. SHOB defines a weak consistency memory model where the user controls the amount of inconsistency due to caching and prefetching. The model is well suitable to implement iterative numerical algorithms. Experimental results of the methodology are presented in the case of a uniform multi-grid method to solve partial differential equations.

A Secure Cloud Manager for the X1.V1 Platform

The increasing number and complexity of e-health services provided to citizens push healthcare organizations to adopt powerful computing systems to deal with the resulting workload. The adoption of the Cloud to host such services is a promising solution to address the increasing demand for computational power and also to deal with expected or unexpected computational peaks. This paper proposes a framework that allows the execution on the Cloud of the X1.V1 platform, which is a commercial product that supports a number of e-health services as well as the interoperability among different healthcare environments. This framework is meant to enable an easy and quick management of the Cloud resources allocated to the X1.V1 platform, in order to enhance the platform performances and optimize resources utilization. The design of the framework takes into account security aspects as well, because unauthorized accesses could lead to serious inefficiencies of the e-health services.

MPI on a virtual shared memory

Publisher Summary To show the advantages of an implementation of MPI on top of a distributed shared memory, this chapter describes MPI SH , an implementation of MPI on top of DVSA, a package to emulate a shared memory on distributed memory architecture. DVSA structures the shared memory as a set of variable size areas and defines a set of operations each involving a whole area. The various kinds of data to implement MPI— that is, to handle a communicator, a point to point or a collective communication, are mapped onto these areas, such that a large degree of concurrency, and hence a good performance, can be achieved. Performance figures show that the proposed approach may achieve better performances than more traditional implementations of collective communication. To enhance the portability of the MPI support across distinct physical architectures supporting DVSA, the implementation of MPI SH exploits the DVSA constructs only. As an example, MPI non blocking communications are defined through DVSA non blocking primitives, even if a thread mechanism supported by the architecture might be more efficient.

A Parallel Programming Tool for SAR Processors

In the context of Italian Space Agency COSMO SkyMed project a quantitative and qualitative study of a set of image processing algorithms for SAR Processors has been carried out. The algorithms showed some interesting patterns in terms of structure and parallelism exploitation. During the activity of prototyping and analysis, an abstraction (SPE Chain Model) of the algorithmic behaviour has been defined in order to simplify performance modeling, design and implementation of parallel image processing algorithms. According to the defined abstraction, a parallel programming tool (SPE- Sar Parallel Executor) has been developed. SPE enables the implementation of efficient, structured and object oriented parallel image processing algorithms conforming to the SPE Chain Model and reuse of pre-existing sequential code. A set of image processing algorithms belonging to different classes of applications have been tested to validate both the SPE Chain Model and the SPE programming tool. The results show that no significant difficulties arise in the porting of already existing code to SPE and that writing new parallel algorithms is intuitive and productive and provides, at the same time, concrete high performance solutions required in real-time industry environments.