Issmail El Hallaoui
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Cahiers du GERAD
This study explores accelerating strategies in column generation (CG) to effectively solve online dial-a-ride problems in large-scale ride-sharing systems. ...
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This paper tackles a complex variant of the unit commitment (UC) problem at Hydro-Quebec, referred to as the transient stability constrained unit commitmen...
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This paper describes a planning problem faced by a fast-growing petroleum company in West Africa. The problem is a complex variant of the petrol station repl...
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Efficiently solving a vehicle routing problem (\(\mathcal{VRP}\)
) in a practical runtime is a critical challenge for delivery management companies. This pa...
The truck loading and inventory routing problems are the two most important decisions made by companies replenishing petrol stations. This paper investigates...
BibTeX referenceAlgorithme primal ajoutant des variables pour le problème du partitionnement d'ensemble généralisé
Le problème du partitionnement d'ensemble est un problème de programmation en nombres entiers très étudié. Le problème consiste à trouver une partition de tâ...
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Incentive-based demand response aggregators are widely recognized as a powerful strategy to increase the flexibility of residential community microgrid (RCM)...
BibTeX referenceThe primal Benders decomposition
Benders decomposition has been applied significantly to tackle large-scale optimization problems with complicating variables, which, when temporarily fixed, ...
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Operations research specialists at the OCP Group, the Mohammed VI Polytechnic University, and the Polytechnique Montreal operationalized a system optimizing ...
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Perturbations are universal in supply chains, and their appearance is getting more frequent in the past few years. These perturbations affect industries and ...
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This paper develops an efficient hybrid algorithm to solve the credit scoring problem. We use statistical mathematical programming to develop new classificat...
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We consider the problem of minimizing the linear cost of multistate homogeneous series-parallel system given the nonlinear reliability constraint on the syst...
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This paper presents a multiobjective, mixed-integer linear programming (MILP) model that integrates production scheduling, inventory management, and vessel a...
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The parameter configuration problem consists of finding a parameter configuration that provides the most effective performance by a given algorithm. This pap...
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For a simple connected graph \(G\)
, let \(D(G), ~Tr(G)\)
, \(D^{L}(G)=Tr(G)-D(G)\)
, and \(D^{Q}(G)=Tr(G)+D(G)\)
be the distance matrix, the diagonal m...
For a graph \(G\)
, the signless Laplacian matrix \(Q(G)\)
defined as \(Q(G) = D(G) + A(G)\)
, where \(A(G)\)
is the adjacency matrix of \(G\)
and `...
The primal simplex algorithm is still one of the most used algorithms by the operations research community. It moves from basis to adjacent one until optimal...
BibTeX referenceParallel stimulation of disruptions for personnel scheduling in a flexible working environment
Personnel scheduling aims to determine least-cost personnel schedules to meet the demand for employees in each period of a planning horizon. In this article,...
BibTeX referenceAn improved integral column generation algorithm using machine learning for aircrew pairing
The crew pairing problem (CPP) is solved in the first step of the crew scheduling process. It consists of creating a set of pairings (sequence of flights, co...
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Given a set of predefined duties and groups of drivers, the duty assignment problem with group-based driver preferences (DAPGDP) aims at building rosters tha...
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Overbooking is a common practice in the air cargo industry because booked and actual demands often differ greatly. As a consequence, in case of excessive ove...
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The integral column generation algorithm (ICG) was recently introduced to solve set partitioning problems involving a very large number of variables. This pr...
BibTeX referenceSolving a real-world multi-period petrol replenishment problem with complex loading constraints
In this paper, we solve a rich real-word Multi-Depot Multi-Period Petrol Replenishment Problem with a heuristic based on Branch-and-Price heuristic. The netw...
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In the present paper, we prove lower and upper bounds for each of the ratios \(GA/\delta\)
, as well as a lower bound on \(GA/\sqrt{\delta}\)
, in terms of...
Personnel scheduling consists of determining least-cost work schedules to cover the demand of multiple jobs expressed in number of employees per job and peri...
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Given a set of duties to be operated over a cyclic one-week horizon and groups of drivers with similar characteristics, the cyclic bus driver rostering probl...
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Operations Research (OR) has a very important role to play in credit scoring for building models that can help the lending organization to make a good decisi...
BibTeX referenceA game theoretic analysis for community microgrid: Architecture, formulation and optimization
Microgrid, a promising component of smart grid, will potentially yield a free electricity market. This paper proposes a novel construction for a community mi...
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This paper develops an exact method for the redundancy allocation problem (RAP) for multistate homogeneous series-parallel systems. The problem aims to min...
BibTeX referenceDistributed integral column generation
The Integral Simplex Using Decomposition (ISUD) algorithm has been developed recently to solve large set partitioning problems (SPPs) in a primal way, i.e.,...
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The primal adjacency-based algorithm and the multi-directional dynamic programming algorithm are two exact methods that have recently been developed to effic...
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Personnel scheduling aims at determining the cheapest work schedules to cover the demand for one or more tasks at each period of a given horizon. During the ...
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Clustering is the subject of active research in several fields such as operations research, statistics, pattern recognition, and machine learning. The range ...
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This paper addresses the winner determination problem (WDP) for TL transportation procurement auctions under uncertain shipment volumes and uncertain carrier...
BibTeX referenceA primal adjacency-based algorithm for the shortest path problem with resource constraints
The shortest path problem with resource constraints (SPPRC) is often used as a subproblem within a column generation approach for routing and scheduling prob...
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The shortest path problem with resource constraints finds the least cost path between two nodes in a network while respecting constraints on resource consump...
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Given an integer solution, the integral simplex using decomposition (ISUD) seeks a descent direction that leads to an improved adjacent integer solution. It ...
BibTeX referenceIntegral column generation
The integral simplex using decomposition (ISUD) algorithm was recently developed to solve efficiently set partitioning problems containing a number of variab...
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The bid construction problem (BCP) for combinatorial total truckload transportation service procurement auctions consists of determining one or several bids ...
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Personnel scheduling consists of determining least-cost employee work schedules to cover the demand of one or several jobs in each period of a time horizon. ...
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In this paper, we introduce a general framework for vector space decompositions that decompose the set partitioning problem into a reduced problem, defined...
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To solve integer linear programs, primal algorithms follow an augmenting sequence of integer solutions leading to an optimal solution. In this work, we focu...
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The integral simplex using decomposition (ISUD) algorithm <font size=2>[Zaghrouti, A., Soumis, F., Elhallaoui, I.: Integral simplex using decomposition for t...
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Starting from the improved primal simplex (IPS) decomposition, introduced by Elhallaoui et al. (2011) to tackle degeneracy in general linear programs, we int...
BibTeX referenceMultilevel hybrid method for solving buffer sizing and inspection stations allocation problems
This paper develops an efficient method to solve a typical combinatorial optimization problem that is frequently encountered when designing high levels of pr...
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We propose a primal algorithm for the Set Partitioning Problem based on the Integral Simplex Using Decomposition of Zaghrouti et al. (2014). We present the a...
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Since its introduction in 1969, the set partitioning problem has received much attention, and the structure of its feasible domain has been studied in detail...
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The buffer sizing problem in unreliable production lines is a complex combinatorial optimization problem. In the formulation of the problem, the system consi...
BibTeX referenceBuffer Dimensioning and Control Stations Positioning with a Space Partitioning-Tabu Search Approach
We propose an efficient heuristic method based on Space Partitioning (SP) and Tabu Search (TS) to solve the buffer sizing problem in unreliable production li...
BibTeX referenceAn Exact Method for Solving the Buffer Sizing and Inspection Stations Allocations Problem
An unreliable single part type transfer line with fixed inter machine buffer sizes is considered. In general, imperfect machines operating with imperfect raw...
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Since the 1970's, several authors have studied the structure of the set partitioning polytope and proposed adaptations of the simplex algorithm that find an ...
BibTeX referenceIntegrated Airline Crew Scheduling: A Bi-Dynamic Constraint Aggregation Method using Neighborhoods
The integrated crew scheduling (ICS) problem consists of determining, for a set of available crew members, least-cost schedules that cover all flights and re...
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Traditionally, the airline crew scheduling problem has been decomposed into a crew pairing and a crew assignment problem that are solved sequentially. The f...
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The bidline scheduling problem with equity arises in several North American airlines. It consists of determining anonymous monthly schedules, called bidlines...
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Since its appearance in 1947, the primal simplex algorithm has been one of the most popular algorithm for solving linear programs. It is very efficient wh...
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Column generation is often used to solve problems involving set partitioning constraints, such as vehicle routing and crew scheduling problems. When these co...
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