Antonio Iovanella

Grid scheduling by on-line rectangle packing

The Grid computing paradigm is originated from a new computing infrastructure for scientific research and cooperation, and is becoming an established technology for large-scale resource sharing and distributed integration. Two main problems arise: how to efficiently allocate resources to tasks and, after this, how to schedule them. In this article we propose to solve the scheduling phase by means of rectangle packing algorithms. In particular, two on-line rectangle packing algorithms are proposed with the objective of maximizing the system efficiency. A wide computational analysis is provided. The performances of the proposed algorithms are first compared with those of known algorithms on benchmark instances for rectangle packing, and then are evaluated on different Grid scheduling scenarios associated with different processing and dataset environments.

Scheduling of Independent Dedicated Multiprocessor Tasks

We study the off and on-line versions of the well known problem of scheduling a set of n independent multiprocessor tasks with pre-specified processor allocations on a set of identical processors in order to minimize the makespan. Recently, in [12], it has been proven that in the case when all tasks have unit processing time the problem cannot be approximated within a factor of m1/2 - ?, neither for some ? > 0, unless P= NP; nor for any ? > 0, unless NP=ZPP. For this special case we give a simple algorithm based on the classical first-fit technique. We analyze the algorithm for both tasks arrive over time and tasks arrive over list on-line scheduling versions, and show that its competitive ratio is bounded by 2?m and 2?m + 1, respectively. Here we also use some preliminary results on (vertex) coloring of k-tuple graphs. For the case of arbitrary processing times, we show that any algorithm which uses the first-fit technique cannot be better than m competitive. Then, by using our split-round technique, we give a 3?m-approximation algorithm for the off-line version of the problem. Finally, by using some ideas from [20], we adapt the algorithm to the on-line case, in the paradigm of tasks arriving over time in which the existence of a task is unknown until its release date, and show that its competitive ratio is bounded by 6?m. Due to the conducted experimental results, we conclude that our algorithms can perform well in practice.

Some spin glass ideas applied to the clique problem

In this paper we introduce a new algorithm to study some NP-complete problems. This algorithm is a Markov Chain Monte Carlo (MCMC) inspired by the cavity method developed in the study of spin glass. We will focus on the maximum clique problem and we will compare this new algorithm with several standard algorithms on some DIMACS benchmark graphs and on random graphs. The performances of the new algorithm are quite surprising. Our effort in this paper is to be clear as well to those readers who are not in the field.

Technology transfer in innovation networks: An empirical study of the Enterprise Europe Network

This article offers a network perspective on the collaborative effects of technology transfer, providing a research methodology based on the network science paradigm. We argue that such an approach is able to map and describe the set of entities acting in the technology transfer environment and their mutual relationships. We outline how the connections’ patterns shape the organization of the networks by showing the role of the members within the system. By means of a case study of a transnational initiative aiming to support the technology transfer within European countries, we analyse the application of the network science approach, giving evidence of its relative implications.

Lower bound algorithms for multiprocessor task scheduling with ready times

In this paper, we deal with multiprocessor task scheduling with ready times and prespecified processor allocation. We consider an on-line scenario where tasks arrive over time, and, at any point in time, the scheduler only has knowledge of the released tasks. An application of this problem arises in wavelength division multiplexing broadcasting where the main future will be in the so-called one-to-many transmission. We propose algorithms to find lower bounds of the minimum makespan, and present experiments on various scenarios.

On the influence of nodes' characteristic in inter-organisational innovation networks structure

This paper studies inter-organisational innovation networks, investigating the relations between the structure of the connections among members and a given nodes characteristic. Such relations are used to provide some insights into the attitude of network innovation. We propose an original methodology that considers nodes belonging to two different classes detecting the available configurations. The intensity of connections, as an additional layer of information, is also included to examine its relative influence on the network topology. We complete the analysis through the introduction of a qualitative intensity/connectance matrix that attempts to connote the innovation attitude of the network. We test the methodology on a real case study, discussing the detected configuration and the implication in terms of innovation attitude.

Organizing Collaboration in Inter-Organizational Innovation Networks, from Orchestration to Choreography

This paper introduces the concept of choreography with respect to interorganizational innovation networks, as they constitute an attractive environment to create innovation in different sectors. We argue that choreography governs behaviours by shaping the level of connectivity and cohesion among network members. It represents a valid organizational system able to sustain some activities and to reach effects generating innovation outcomes. This issue is tackled introducing a new framework in which we propose a network model as prerequisite for our hypothesis. The analysis is focused on inter-organizational innovation networks characterized by the presence of hubs, semi-peripheral and peripheral members lacking hierarchical authority. We sustain that the features of a network, bringing to synchronization phenomena, are extremely similar to those existing in innovation network characterized by the emergence of choreography. The effectiveness of our model is verified by providing a real case study that gives preliminary empirical hints on the network aptitude to perform choreography. Indeed, the innovation network analysed in the case study reveals characteristics causing synchronization and consequently the establishment of choreography.

Some Insights into the Relevance of Nodes’ Characteristics in Complex Network Structures

Network structures describe a variety of systems and it is crucial to recognise essential functionalities that affect the dynamic of interactions. Nodes are often identified by certain characteristics, such as age or gender, and the tendency to link nodes with similar features is referred to as homophily. To verify which characteristic is able to address such behaviour has a computational complexity that becomes hard for large networks. In this paper we present a methodology that can be used as a pre-processing tool in order to avoid the study of non-effective nodes’ characteristics.

An on-line algorithm for the rectangle packing problem with rejection

In this paper an on-line algorithmf or the Rectangle Packing Problemi s presented. The method is designed to be able to accept or reject incoming boxes to maximize efficiency. We provide a wide computational analysis showing the behavior of the proposed algorithmas well as a comparison with existing off-line heuristics.

Heuristic multiobjective search for hazmat transportation problems

This paper describes the application of multiobjective heuristic search algorithms to the problem of hazardous material (hazmat) transportation. The selection of optimal routes inherently involves the consideration of multiple conflicting objectives. These include the minimization of risk (e.g. the exposure of the population to hazardous substances in case of accident), transportation cost, time, or distance. Multiobjective analysis is an important tool in hazmat transportation decision making. This paper evaluates the application of multiobjective heuristic search techniques to hazmat route planning. The efficiency of existing algorithms is known to depend on factors like the number of objectives and their correlations. The use of an informed multiobjective heuristic function is shown to significantly improve efficiency in problems with two and three objectives. Test problems are defined over random graphs and over a real road map.