Paolo Palazzari

Human exposure to the near field of radiobase antennas - a full-wave solution using parallel FDTD

The problem of human exposure to the near field of radiobase antennas is a complex and challenging task. A numerical full-wave solution is highly recommended because of the accuracy needed. Unfortunately, the problem is computationally heavy. In this paper, a parallel finite-difference time-domain tool is proposed for the solution of the addressed problem so that the use of supercomputing platforms is combined with appropriate numerical human phantoms. Results demonstrate the good accuracy of the proposed solution. A detailed discussion is presented on the case of human exposure to real radiobase antennas, as well as on some critical issues concerning safety standards.

Real time pipelined system design through simulated annealing

Abstract This paper is concerned with automatic pipeline implementation of a program subject to some real time (RT) constraints; the program is described through a Control Data Flow Graph (CDFG). We have developed a mapping methodology which assigns to each instruction of CDFG a time step and a HW resource for its execution. We have defined the space Ω of all the possible feasible mappings, as well as an adjacency criterion on it and a cost function evaluating the quality of the mappings. We have minimized the cost function through a Simulated Annealing algorithm. The minimization process returns a mapping which satisfies all RT constraints, has minimal schedule length and minimal HW resource requirement. In order to show the capabilities of the proposed mapping methodology, we apply it to a graph with 50 nodes and several RT constraints: the obtained mapping gives a pipelined execution modality of the graph which satisfies all the given RT constraints.

Synthesis of pipelined systems for the contemporaneous execution of periodic and aperiodic tasks with hard real-time constraints

Summary form only given. We address the design of pipelined systems able to sustain the throughput of a given periodic task and, at the same time, to serve aperiodic requests associated with hard real-time constraints. The proposed method is based on the allocation of the global graph (periodic and aperiodic tasks), over-dimensioning the design of the system devoted to process the periodic task, deserving the unused parts of the resources to the management of aperiodic requests. A formal definition of such a mapping problem, together with the formalization of the searching space, is given. The searching space is structured in a way such as the minimization process moves toward a solution, which satisfies, if possible, all the real-time constraints and has minimal HW requirements. Once formulated as a minimization problem, the pipelined architecture and the corresponding scheduling are determined by means of a simulated annealing algorithm. A theorem is given to ensure that all the feasible mappings are reachable in the optimization process.

OpenFPGA CoreLib core library interoperability effort

This paper begins by summarizing the goals of the OpenFPGA CoreLib Working Group to facilitate the interoperability of FPGA circuit cores within a variety of FPGA design tools, including high-level programming tools targeting FPGA architectures. This effort is contrasted with other IP reuse efforts. The paper reviews the current approach used by several high-level language compilers to integrate IP within their tool. The CoreLib approach for standardizing this IP integration is proposed followed by an example that demonstrates its utility. Finally, the current state of the effort and future plans are presented.

Hyper-systolic matrix multiplication

Abstract A novel parallel algorithm for matrix multiplication is presented. It is based on a 1-D hyper-systolic processor abstraction. The procedure can be implemented on all types of parallel systems.

The DIESIS Approach to Semantically Interoperable Federated Critical Infrastructure Simulation

Critical infrastructures (CI) such as telecommunication or the power grids and their dependencies are getting increasingly complex. Understanding these – often indirect –dependencies is a vital precondition for the prevention of cross sector cascading failures of CI. Simulation is an important tool for CI dependency analysis, the test of methods for risk reduction, and as well for the evaluation of past failures. Moreover, interaction of such simulations with external threat models, e.g., a river flood model and economic models, may assist in what-if decision-making processes. The simulation of complex scenarios involving several different CI sectors requires the usage of heterogeneous federated simulations of CI. However, common standards for modelling and interoperability of such federated CI simulations are missing. In this paper, we present a novel approach for coupling CI simulations, developed and realised in the EU project DIESIS. The DIESIS core technologies for coupling CI simulations include a middleware that enables semantic interoperability of the federate simulators, a systematic, service-oriented approach to set up and run such federations, and, most importantly, a scenario-based architecture concept for modelling and federated simulation of CI. The architecture foresees a flexible pair-wise (lateral) coupling of simulators. DIESIS has implemented a demonstrator as a proof of concept for its approach and technologies, by coupling four different simulation systems (three interacting CIs and an external, common threat). In this paper, we focus on the architectural concept and the interoperability middleware that realises this concept and allows the coupling of heterogeneous simulation systems using various time and data models. We show how the ontology-based Knowledge Based System (KBS) is integrated and used in the overall system. Then, we discuss the basic technical concepts as well as the results obtained with the demonstrator. The proposed architecture is open for further extensions. Ultimately, the proposed approach shall form the basis of a future standard coupling middleware for federated CI simulations.

A new method for optimization of allocation and scheduling in real time applications

Performance improvements achievable through parallel processing are useful in real time (RT) environments. The paper describes a method to map (i.e. allocate and schedule) a program with some RT constraints into a parallel system. We formulate the mapping problem as a minimization problem, defining a new cost function whose minimization leads to the optimal mapping of the program into the parallel system. The searching space over which the minimization must be carried out is defined; this space encloses all the feasible allocation and scheduling modalities for the program in the parallel system. The minimization is carried out through a simulated annealing algorithm, so we define an adjacency criterion on the searching space. Some examples illustrating the capabilities of the proposed method are presented.

A new crossover operator for genetic algorithms

Starting from a mathematical reinterpretation of the classical crossover operator, a new type of crossover is introduced. The proposed new crossover operator gives better performances than the classical 1 point, 2 point or uniform crossover operators. A theoretical investigation of the behaviour of the new crossover is presented. Compared to the classical crossover operators, it allows better exploration of the searching space and gives better results. Some comparative results relative to the optimization of test functions taken from literature are given.

An ontological approach to simulate critical infrastructures

Abstract This paper presents a Knowledge Base System (KBS) as a key component of a federated simulation framework aimed at investigating the dependencies among Critical Infrastructures (CIs). The KBS, based on the ontological formalism, represents the properties and the relations of each simulation domain and the dependency relations among different domains. Some auxiliary data structures, necessary to model the interaction among the simulators of different CIs, have been defined and have been populated through suitable queries to the KBS. The adoption of the ontological formalism allowed the definition of a common formalism to deal with the heterogeneity arising from the presence of different domains.

Automatic mapping of system of N-dimensional affine recurrence equations (SARE) onto distributed memory parallel systems

The automatic extraction of parallelism from algorithms, and the consequent parallel code generation, is a challenging problem. We present a procedure for automatic parallel code generation in the case of algorithms described through a SARE (Set of Affine Recurrence Equations). Starting from the original SARE description in an N-dimensional iteration space, the algorithm is converted into a parallel code for an (eventually virtual) m-dimensional distributed memory parallel machine (m<N). We demonstrate some theorems which are the mathematical basis for the proposed parallel generation tool. The projection technique used in the tool is based on the polytope model. Some affine transformations are introduced to project the polytope from the original iteration space onto another polytope, preserving the SARE semantic, in the time-processor (t,p) space. Points in (t,p) are individuated through the m-dimensional p coordinate and the n-dimensional t coordinate, resulting in N=n+m. Along with polytope transformation, a methodology to generate the code within processors is given. Finally, a cost function, used to guide the heuristic search for the polytope transformation and derived from the actual implementation of the method on an MPP SIMD machine, is introduced.