We consider the online scheduling problem of parallel jobs on parallel machines, P |online − list,mj |Cmax. For this problem we present a 6.6623-competitive algorithm. This improves the best known 7competitive algorithm for this problem. The presented algorithm also applies to the special case where machines are ordered on a line and only adjacent machines can be assigned to a job and, therefor...

In this paper we introduce a hyperheuristic to solve hard strip packing problems. The hyperheuristic manages a sequence of greedy low-level heuristics, each element of the sequence placing a given number of objects. A low-level solution is built by placing the objects following the sequence of low-level heuristics. The hyperheuristic performs a hill-climbing algorithm on this sequence by testin...

In this paper we introduce a collaboration framework for hyperheuristics to solve hard strip packing problems. We have designed a genetic based hyperheuristic to cooperate with a hill-climbing based hyperheuristic. Both of them use the most recently proposed low-level heuristics in the literature. REVAC, which has recently been proposed for tuning [18], has been used to find the best operators ...

Abstract We study the Non-preemptive Peak Demand Minimization (NPDM) problem, where we are given a set of jobs, specified by their processing times and energy requirements. The goal is to schedule all jobs within fixed time period such that peak load (the maximum total requirement at any time) minimized. This problem has recently received significant attention due its relevance in smart-grids. ...

In this paper we propose an iterative hybrid heuristic approach consisting of two phases to solve the Rectangle Packing Problem. In the first phase, a strip width value W is fixed and the corresponding Strip Packing Problem is solved using an efficient hybrid GRASP-VNS heuristic. In the second one, a new value W is determined. The above phases are repeated until the stopping condition is met. T...

We consider the 3-staged Strip Packing Problem, in which rectangular items have to be arranged onto a rectangular strip of fixed width, such that the items can be obtained by three stages of guillotine cuts while the required strip height is to be minimized. We propose a new logic-based Benders decomposition with two kinds of Benders cuts and compare it with a compact integer linear programming...

This article addresses the Strip Packing Problem with Unloading Constraints (SPU). In this problem, we are given a strip of fixed width and unbounded height, and n items of C different classes. As in the well-known two-dimensional Strip Packing problem, we have to pack all items minimizing the used height, but now we have the additional constraint that items of higher classes cannot block the w...