S. Di Gregorio - Academia.edu (original) (raw)

Papers by S. Di Gregorio

Developments in Language Theory, 2018

Cellular Automata (CA) are both a parallel computational paradigm and an archetype for modelling ... more Cellular Automata (CA) are both a parallel computational paradigm and an archetype for modelling complex systems, that evolve on the basis of local interactions. CA can embody different numeral representations and perform related basic arithmetical operations. However, conventional numeral representations are thought as intrinsically sequential in such operations, which implies that CA parallelism is underexploited when CA evolution mimics the sequentiality of calculation, while some redundant numeral representations could exalt the CA parallelism in a space/time trade-off, where the time complexity of some operations is constant on input length. The problem then arises when the result of an operation must be utilized in the conventional representation since, usually, the migration toward an advantageous redundant numeric representation is costless, but the inverse one implies necessarily a cost that cancels the benefits in terms of computation time. This paper explores the properties of the conventional binary positional representation embodied in a CA together with the addition operation and the corresponding ones of a redundant binary positional representation, the rules and time cost for the passage from conventional numeral system to redundant one and vice versa. The results permit to individuate the CA computation context, when redundancy could be exploited advantageously. It regards cases where a longest sequence of additions (or operations based on addition, e.g., fast Fourier transforms) has to be performed in well-defined short times as for the automatic control of mobile devices.

EGU General …, 2010

A Cellular Automata model was developed for modelling the flow of snow avalanches. The model is b... more A Cellular Automata model was developed for modelling the flow of snow avalanches. The model is based on SCIDDICA SS2, a numerical code recently developed for the simulation of subaerial and subaqueous flow-like landslides. Basically, the model ...

Parallel Computing - Fundamentals and Applications - Proceedings of the International Conference ParCo99, 2000

Processes of Emergence of Systems and Systemic Properties - Towards a General Theory of Emergence - Proceedings of the International Conference, 2009

Systemics of Emergence: Research and Development, 2006

Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere, 2001

A Cellular Automata model for soil erosion by water, SCAVATU, was developed. It involves a larger... more A Cellular Automata model for soil erosion by water, SCAVATU, was developed. It involves a larger number of states in comparison to the previous models: altitude, vegetation density, water depth, water run-up height, infiltration, outflow towards neighbouring cells, inflows, eroded material, sediment transport, deposited material, sediment transport fluxes. It was applied to the Armaconi basin, Calabria, Italy, considering some of the most significant processes of the phenomenon: water flow, infiltration, soil erosion by water flow, sediment transport and deposition. Simulations gave encouraging results, in agreement with the findings of other studies.

Lecture Notes in Computer Science, 2007

Forecasting through simulations the shape of lava invasions in a real topography represents a cha... more Forecasting through simulations the shape of lava invasions in a real topography represents a challenging problem, especially considering that the phenomenon usually evolves for a long time (e.g. from a few to hundreds of days) and on very large areas. In the latest years, Cellular Automata (CA) have been well recognized as a valid computational approach in lava flow modelling. In this paper we present some significant developments of SCIARA, a family of deterministic CA models of lava flows which are optimized for a specific scenario through the use of a parallel genetic algorithm. Following a calibration-validation approach, the model outcomes are compared with three real events of lava effusion.

Submarine Mass Movements and Their Consequences, 2010

The analysis of the propagation phase plays a fundamental role in the assessment and forecasting ... more The analysis of the propagation phase plays a fundamental role in the assessment and forecasting of risks related to the occurrence of submerged and coastal landslides. At present there are few numerical models able to simulate the propagation of such a type of events. This paper presents fully 3D models and approaches developed by the authors and suitable for the simulation of both completely subaqueous landslides and combined subaerial-submerged ones (i.e. coastal landslides with a subaerial source which propagate underwater). A Cellular Automata model is described which has been specifically designed for combined subaerial-submerged landslides. Moreover, a new approach able to simulate submerged mass movements using commercial 3D software, originally developed for subaerial landslides, is presented. Calibration and validation of these models upon a real and well constrained coastal debris flow at Lake Albano (Rome, Italy) is also presented.

Lecture Notes in Computer Science, 1996

This paper describes CAMEL, a parallel environment for designing scientific applications based on... more This paper describes CAMEL, a parallel environment for designing scientific applications based on the cellular automata mathematical model. CAMEL is an interactive environment designed to support the development of high performance applications in science and engineering. It offers the computing power of a highly parallel computer, hiding the architecture issues from a user. The system can be used both as a tool to model dynamic complex phenomena and as a computational model for parallel processing. By CAMEL a user might write programs to describe the actions of thousands of simple active agents, then observe the global complex evolution that arise from all the local interactions. The paper presents the programming environment and a significant application in the area of soil decontamination.

IEEE Computational Science and Engineering, 1996

In this paper we describe CAMEL, an interactive parallel environment based on the cellular automa... more In this paper we describe CAMEL, an interactive parallel environment based on the cellular automata theory. CAMEL is a tool designed to support the development of high performance applications in science and engineering. It offers the computing power of a highly parallel computer, hiding the architecture issues from a user. The system can be used both as a tool to model dynamic complex phenomena and as a computational model for parallel processing. CAMEL implements a cellular automaton as a SPMD (Single Program Multiple Data) program and includes a load balancing strategy to equally distribute the computation load over the processing elements. By CAMEL a user might write programs to describe the actions of thousands of simple active objects, then observe the global complex evolution that arise from all the interactions. The paper presents a set of applications in significant areas such as lava flow, landslides, freeway traffic, image processing, and genetic algorithms where CAMEL has been successfully utilized to solve complex problems.

Lecture Notes in Computer Science, 2014

ABSTRACT Lahars represent one of the most destructive natural disasters as number of casualties i... more ABSTRACT Lahars represent one of the most destructive natural disasters as number of casualties in the world. Secondary lahars are very complex surface flows, which originate from the mobilization of pyroclastic deposits by exceptional heavy rainfalls. Simulation of secondary lahars could be an important tool for risk management in threatened regions. Multicomponent (macroscopic) Cellular Automata (CA) characterize a methodological approach for modelling large scale (extended for kilometers) complex phenomena, that evolve on the basis of local interactions. A preliminary three dimension CA model was developed and partially applied on a real event: the 2005 secondary lahar of Vascún Valley, Ecuador. Simulations are satisfying, a comparison is performed with the previous successful two dimensions model Titan2D, based on PDE, together with simulation results of the same event.

Cellular Automata are an established formal support for modelling traffic. STRATUNA is a Cellular... more Cellular Automata are an established formal support for modelling traffic. STRATUNA is a Cellular Automata model for simulating two/three lanes highway traffic. It is based on an extensive specification of the driver response to the surrounding conditions. The model is deterministic with regard to driver behaviour, even if values of parameters ruling the reactivity level of the drivers are assigned stochastically. Probability distribution functions were deduced by field data and applied to vehicular flow generation (vehicle types, driver desired speed, entrance-exit gates). A partial implementation of STRATUNA was performed and applied to Italian highway A4 from Venice to Trieste. Simulations were compared with available field data with results that may be certainly considered encouraging in this initial implementation.