# Michel ToulouseHanoi University of Science and Technology · Information system

Michel Toulouse

Phd

## About

81

Publications

14,943

Reads

**How we measure 'reads'**

A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more

2,089

Citations

Citations since 2017

Introduction

Additional affiliations

March 2020 - present

September 2014 - February 2020

August 2008 - May 2014

## Publications

Publications (81)

Purpose
Sharding of blockchains consists of partitioning a blockchain network into several sub-networks called “shards,” each shard processing and storing disjoint sets of transactions in parallel. Sharding has recently been applied to public blockchains to improve scalability through parallelism. The throughput of sharded blockchain is optimized w...

Public blockchains are decentralized networks where each participating node executes the same decision-making process. This form of decentralization does not scale well because the same data are stored on each network node, and because all nodes must validate each transaction prior to their confirmation. One solution approach decomposes the nodes o...

Public blockchains are decentralized networks where each participating node executes the same decision-making process. This form of decentralization does not scale well because the same data are stored on each network node, and because all nodes must validate each transaction prior to their confirmation. One solution approach decomposes the nodes o...

As the world was hit hard by the coronavirus pandemic in 2020, many of our authors struggle with a new difficult time. Though Vietnam survived the last two waves of the pandemic, we had to take into account the restriction of international travels put by many universities and companies worldwide and the uncertainty of government measures in Novembe...

Distributed computing network-systems are modeled as directed/undirected graphs with vertices representing compute elements and adjacency-edges capturing their uni- or bi-directional communication. To quantify an intuitive tradeoff between two graph-parameters: minimum vertex-degree and diameter of the underlying graph, we formulate an extremal pro...

Distributed function computation has a wide spectrum of major applications in distributed systems. Distributed computation over a network-system proceeds in a sequence of time-steps in which vertices update and/or exchange their values based on the underlying algorithm constrained by the time-(in)variant network-topology. Distributed computing netw...

Global-scale Internet of Things (IoT) applications commonly process a huge amount of data and quickly provide useful information (to users) and instructions to monitor or control the physical world; most of these services are required to be of low latency while satisfying resource constraints (computing, storage, networking). In order to reduce com...

In this paper, we introduce the minimum graph partition problem with basis. A graph partition with basis is a partition of the node set into connected parts, each contains exactly one element of the basis set. The objective is to minimize the size of the largest part. We propose three different mixed-integer linear models to solve this problem, enh...

Parallel and distributed computing network-systems are modeled as graphs with vertices representing compute elements and adjacency-edges capturing their uni- or bi-directional communication. Distributed function computation covers a wide spectrum of major applications, such as quantized consensus and collaborative hypothesis testing, in distributed...

Fog computing is a promising technology for global-scale Internet of Things (IoT) applications as it allows moving resources (computing, storage, networking) close to IoT devices, thus helping to reduce communication latency, network load, energy consumption and operational cost. In order to realize these advantages, application and management serv...

Distributed computing network-systems are modeled as graphs with vertices representing compute elements and adjacency-edges capturing their uni- or bi-directional communication. Distributed function computation has a wide spectrum of major applications in distributed systems. Distributed computation over a network-system proceeds in a sequence of t...

Finite time consensus algorithms compute consensus values exactly and in a finite number of steps, contrasting with asymptotic consensus algorithms. In the literature, there exists few approaches deriving finite time convergence for discrete consensus algorithms. In this paper we focus on an analysis of finite time convergence based on the observab...

This work concerns distributed consensus algorithms and application to a network intrusion detection system (NIDS) [21]. We consider the problem of defending the system against multiple data falsification attacks (Byzantine attacks), a vulnerability of distributed peer-to-peer consensus algorithms that has not been widely addressed in its practical...

Urban flood management and mitigation is one of the critical missions to maintain a stable city development. Most of the current available flood mitigation approaches are using data from fixed-site sensor systems which are not only costly but also limited in their coverage. Crowdsourcing is one of the potential approaches for addressing the coverag...

Natural disasters can be mitigated or even anticipated if we have appropriate means, in terms of communications and data sharing models, to collect relevant data in advance or during disaster occurrences, which can be used for supporting disaster prevention and recovery processes. This work proposes a framework that encourages people to collect and...

In a recent work Toulouse et al. [1] introduced a fully distributed network intrusion detection system (NIDS) based on an average consensus algorithm. In this initial work, modules of the NIDS repeatedly average their state with the state of their neighbors to converge asymptotically to a same value, which in turn is used as measurement of some rel...

In this paper, we consider two-tiered city logistics systems accounting for both the inbound and outbound traffic, that have not been taken into account in models and algorithms for vehicle routing research. The problem under study, called the Multi-trip Pickup and Delivery Problem with Time Windows and Synchronization, has two sets of intertwined...

We present a new planning model for freight consolidation carriers, one that links strategic, resource-acquisition and allocation decisions with tactical, service network design-related decisions. Specifically, like service network design models that recognize resource constraints, the model selects services and routes both commodities and the reso...

The purpose of a Network Intrusion Detection System (NIDS) is to monitor network traffic such to detect malicious usages of network facilities. NIDSs can also be part of the affected network facilities and be the subject of attacks aiming at degrading their detection capabilities. The present paper investigates such vulnerabilities in a recent cons...

The paper introduces the first methodology addressing with a single fleet of vehicles the routing of the three different types of transportation demands encountered in City Logistics, inbound, outbound and intra-city traffic. We propose a tabu search meta-heuristic calling on various neighbourhoods, dynamically selected, to provide an efficient sea...

Consensus algorithms provide strategies to solve problems in a distributed system with the added constraint that data can only be shared between adjacent computing nodes. We find these algorithms in applications for wireless and sensor networks, spectrum sensing for cognitive radio, even for some IoT services. However, consensus-based applications...

On-the-fly establishment of multihop wireless access networks (OEMAN) is a new wireless communication approach to quickly establish temporary Internet connectivity in a disaster region. OEMAN creates virtual access points on mobile devices of disaster victims to reach still-alive access points of the Internet so that rescuers can be informed about...

We present a new planning model for freight consolidation carriers, one that links strategic, resource-acquisition and allocation decisions with tactical, service network design related decisions. Specifically, like service network design models that recognize resource constraints, the model selects services and routes both commodities and the reso...

Network intrusion detection is the process of identifying malicious behaviors
that target a network and its resources. Current systems implementing intrusion
detection processes observe traffic at several data collecting points in the
network but analysis is often centralized or partly centralized. These systems
are not scalable and suffer from the...

Maximum likelihood estimation (MLE) is one of the most popular technique in econometric and other statistical applications due to its strong theoretical appeal, but can lead to numerical issues when the underlying optimization problem is solved. We examine in this paper a range of trust region
and line search algorithms and focus on the impact that...

We propose a new population-based hybrid meta-heuristic for the periodic vehicle routing problem with time windows. This meta-heuristic is a generational genetic algorithm that uses two neighborhood-based meta-heuristics to optimize offspring. Local search methods have previously been proposed to enhance the fitness of offspring generated by crosso...

We first present a new service network design model for freight consolidation carriers, one that selects services and routes both commodities and resources needed to support the services that transport them, while explicitly recognizing that there are limits on how many resources are available at each terminal. We next present a solution approach t...

We propose a tabu search meta-heuristic for the Time-dependent Multi-zone Multi-trip Vehicle Routing Problem with Time Windows. Two types of neighborhoods, corresponding to the two sets of decisions of the problem, together with a strategy controlling the selection of the neighborhood type for particular phases of the search, provide the means to s...

This paper proposes a three-phase matheuristic solution strategy for the capacitated multi-commodity fixed-cost network design problem with design-balance constraints. The proposed matheuristic combines exact and neighbourhood-based methods. Tabu search and restricted path relinking meta-heuristics cooperate to generate as many feasible solutions a...

Providing protection in multi-domain optical networks amounts to ensuring protection for the inter-domain connections. Due to scalability issues, almost all previous studies focused on heuristics. In this study, we propose a large scale optimization ILP model, which allows the exact solution of quite large instances, under the assumption of a distr...

Providing protection in multi-domain optical networks involves ensuring protection for inter-domain connections. Due to scalability issues, almost all previous studies focused on heuristics for solving their protection models. In this study, we propose a large scale optimization ILP model, which allows the exact solution of quite large instances. T...

system is a bidding protocol. In the CM system, the auction server receives bids for the available resources and uses some "profit" maximization strategy to select the set of bids that should receive the resources. Because the CM allows the users to bid on different combinations of resources, determining the winning bids becomes NP- complete (San99...

We present a state-of-the-art survey of parallel meta-heuristic strategies, developments, and results. We discuss general
design and implementation principles that apply to most meta-heuristic classes and instantiate these principles for neighborhood
and population-based meta-heuristics. We also identify a number of trends and promising research di...

The complexity of the maximum leaf spanning tree problem for grid graphs is currently unknown. We determine the maximum number of leaves in a grid graph with up to 4 rows and with 6 rows. Furthermore, we give some constructions of spanning trees of grid graphs with a large number of leaves.

Proceedings of the 13th International Conference on Advanced Computing and Applications

Graph coloring is a well-known NP-hard problem with a number of practical applications including timetabling problems. Graph coloring is also difficult to solve because the natural expression of the cost function for this problem is characterized by large plateaus in which solutions "close" to each other have same cost (same number of colors). Plat...

The automated analysis of patients’ biomedical data can be used to derive diagnostic and prognostic inferences about the observed patients. Many noninvasive techniques for acquiring biomedical samples generate data that are characterized by a large number of distinct attributes (i.e., features) and a small number of observed patients (i.e., samples...

Cooperation as problem-solving and algorithm-design strategy is widely used to build methods addressing complex discrete optimization
problems. In most cooperative-search algorithms, the explicit cooperation scheme yields a dynamic process not deliberately
controlled by the algorithm design but inflecting the global behaviour of the cooperative so...

We describe the first multilevel cooperative tabu search for the capacitated multicommodity network design problem. Main design challenges are associated to the specification of the problem instance addressed at each level in cooperation, as well as to the definition of the cooperation operators. The paper proposes a first approach to address these...

The complexity of determining if a Steiner triple system on v = 6n + 3 points contains a parallel class, is currently unknown. In this paper, we show that the problem of determining if a partial Steiner triple system on v = 6n + 3 points contains a parallel class is NP- complete. We also consider the problem of determining the chromatic index of a...

This work describes an adaptation of multilevel search to the covering design problem. The search engine is a tabu search
algorithm which explores several levels of overlapping search spaces of a t–(v,k,λ) covering design problem. Tabu search finds “good” approximations of covering designs in each search space. Blocks from those
approximate solutio...

Decomposing a very complex problem into smaller subproblems that are much easier to solve is not a new idea. The "Parisian Approach"[9] applies this principle extensively to shatter complexity by cutting down the original problem into many small subproblems ...

The maximum leaf spanning tree problem is known to be NP-complete. In [M.S. Rahman, M. Kaykobad, Complexities of some interesting problems on spanning trees, Inform. Process. Lett. 94 (2005) 93–97], a variation on this problem was posed. This variation restricts the problem to bipartite graphs and asks, for a fixed integer K, whether or not the gra...

Multi-player online games (MOGs) have become increas-ingly popular on today's Internet. Meanwhile, the IEEE 802.11 (Wi-Fi) wireless networks have been widely used. We study how well an underlying 802.11g network supports a first-person-shooter (FPS) game, often considered the most demanding MOG in terms of network performance. We measure the latenc...

We have developed a visual syntax for representing concepts that are contingent on temporal properties (time-dependent semantics). A within-group (N=24) experiment was conducted to identify the representations that conveyed best a given semantic. We then applied our representations to the visualization of algorithms in quantum computing and carried...

We propose a multilevel cooperative search algorithm to compute upper bounds for C λ (v,k,t), the minimum number of blocks in a t-(v,k,λ) covering design. Multilevel cooperative search is a search heuristic combining cooperative search and multilevel search. We first introduce a coarsening strategy for the covering design problem which defines redu...

Distributed computer systems may be used in various ways to find good solutions to difficult combinatorial optimization problems. An interesting approach consists in executing concurrently different search methods that exchange information gathered in previously explored regions of the solution space. This cooperation mechanism strongly impacts how...

We present a state-of-the-art survey of parallel meta-heuristic developments and results, discuss general design and implementation principles that apply to most meta-heuristic classes, instantiate these principles for the three meta-heuristic classes currently most extensively used—genetic methods, simulated annealing, and tabu search, and identif...

Distributed computer systems may be used in various ways to nd good solutions to dicult combinatorial optimization problems. An interesting approach consists in executing concurrently dierent search methods that exchange information gathered in previously explored regions of the solution space. This cooperation mechanism strongly impacts how the so...

Our objectives in this paper are twofold: design an approach for the netlist partitioning problem using the cooperative multilevel search paradigm introduced by Toulouse, Thulasiraman and Glover [18], and study the effectiveness of this paradigm for solving combinatorial optimization problems, in particular, those arising in the VLSI CAD area. We p...

The objectives in this paper are twofold: design an approach for
the netlist partitioning problem using the cooperative multilevel search
paradigm introduced by Toulouse et al. and study the effectiveness of
this paradigm for solving combinatorial optimization problems, in
particular, those arising in the very large scale integration (VLSI)
compute...

This paper describes the parallelization of a two-phase metaheuristic for the vehicle routing problem with time windows and a central depot (VRPTW). The underlying objective function combines the minimization of the number of vehicles in the first search ...

Due to the expected scale of the Grid computing Systems, we need to develop highly distributed and extensible resource allocation frameworks for such systems. Microeconomic principles such as auctioning and commodity market are two approaches that are being pursued by several researchers for the Grid resource allocation problem. In this paper we us...

In this paper, we present the overall design for an auctioning based resource trading/acquiring system that can be deployed in wide-area computing systems such as Grid systems. Selecting the winning bids is one of the core issues in any system that utilizes the auctioning paradigm. We identify the unique aspects of our system that impact the winner...

In this paper, we present an adaptation for hypergraph partitioning of the multilevel cooperative search paradigm first introduced by Toulouse, Thulasiraman, and Glover [15]. We also introduce a new approach for coarsening hypergraphs, and describe a parallel implementation of this algorithm on the SGI 02000 system. Experiments on ISPD98 benchmark...

Cooperative search is a parallelization strategy where parallelism is obtained by concurrently executing several search programs for the same optimization problem instance. The programs cooperate by exchanging information on previously explored regions of the solution space. When the sharing of information overlaps among several programs, changes i...

The search history of memory based heuristics like tabu search can be used to design a category of parallel algorithms called cooperative search. These algorithms execute in parallel several search programs on the same optimization problem instance. At run time, the data gathered in the memory by one sequential search program need not be used only...

Metaheuristic parallel search methods -- tabu search, simulated annealing and genetic algorithms, essentially -- are reviewed, classified and examined not according to particular methodological characteristics, but following the unifying approach of the level of parallelization. It is hoped that by examining the commonalities among parallel impleme...

Cooperative search is a parallelization strategy for search algorithms where parallelism is obtained by concurrently executing several search programs. The solution space is implicitly decomposed according to the search strategy of each program. The programs cooperate by exchanging information on previously explored regions of the solution space. I...

Parallel and distributed computer systems are increasingly used to find good solutions to difficult combinatorial optimization problems. An interesting and often used approach consists of executing concurrently different search methods that exchange information gathered in previously explored regions of the solution space. Cooperation among sequent...

The search history of memory based heuristics like tabu search can
be used to design a category of parallel algorithms, called cooperative
search. These algorithms execute in parallel several search programs on
the same optimization problem instance. At run time, the data gathered
in the memory by one sequential search program need not be used only...

In this paper we present a classification of parallel tabu search metaheuristics based, on the one hand, on the control and communication strategies used in the design of the parallel tabu search procedures, and on the other hand, on how the search space is partitioned. These criteria are then used to review the parallel tabu search Implementations...

We study and compare asynchronous parallelization strategies for tabu search, and evaluate the impact on performance and solution quality of some important algorithmic design parameters: number of processors, handling of exchanged information, etc. Parallelization approaches are implemented and compared by using a tabu search algorithm for multicom...

We study and compare synchronous parallelization strategies for tabu search. We identify the most promising parallelization approaches, and evaluate the impact on performance and solution quality of some important algorithmic design parameters: length of the synchronization steps, number of processors, handling of exchanged information, etc. Parall...

Épidaur e, an Actor based programming environment, is presented. The Actor programming approach is combined with the distributed shared memory (DSM) abstraction. Rather than using pr ocesses as compounding structur e, memory structures are used. The defined actor segment is a programming abstraction that goes across process and processor boundaries...

The Agha and Hewitt Actor model [1,3,4] is a natural extension of the object paradigm as we know it to the field of parallel programming. The model respects the primary principles of object-oriented programming, i.e. abstraction of data and encapsulation, making object-oriented programming a good tool for the programming of parallel computers. We d...

We propose a tabu search heuristic for the location/allocation problem with balancing requirements. This problem typically arises in the context of the medium term management of a fleet of containers of multiple types, where container depots have to be selected, the assignment of customers to depots has to be established for each type of container,...