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About

Pedro Rocha. I'm a researcher in the field of operational research, tackling problems related to cutting and packing. Currently working in algorithm optimization for 2D geometrical structures.

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001
Publications

2016

Constraint aggregation in non-linear programming models for nesting problems

Authors
Rocha, P; Gomes, AM; Rodrigues, R; Toledo, FMB; Andretta, M;

Publication
Lecture Notes in Economics and Mathematical Systems

Abstract

2015

Two-Phase Approach to the Nesting problem with continuous rotations

Authors
Rocha, P; Rodrigues, R; Miguel Gomes, AM; Toledo, FMB; Andretta, M;

Publication
IFAC PAPERSONLINE

Abstract
This paper presents an approaches. that assists in producing highly compacted Nesting layouts with irregular pieces using free rotations. This approach consists in the selection and compaction of big pieces in a first phase, while in a second phase, places the remaining small pieces between the big pieces, compacting all of them. The effect of several parameters are analyzed, such as minimum length to be achieved in the first phase, attraction of the pieces to the edges of the container, attraction between each pair of pieces, among others. This approach can provide good compaction results, while improving computational cost in some cases, which cart allow to tackle real world problems more effectively mkt efficiently.

2015

GPU-based computing for nesting problems: The importance of sequences in static selection approaches

Authors
Rocha, P; Rodrigues, R; Miguel Gomes, A; Alves, C;

Publication
Operations Research and Big Data: IO2015-XVII Congress of Portuguese Association of Operational Research (APDIO)

Abstract
In this paper, we address the irregular strip packing problem (or nesting problem) where irregular shapes have to be placed on strips representing a piece of material whose width is constant and length is virtually unlimited. We explore a constructive heuristic that relies on the use of graphical processing units to accelerate the computation of different geometrical operations. The heuristic relies on static selection processes, which assume that a sequence of pieces to be placed is defined a priori. Here, the emphasis is put on the analysis of the impact of these sequences on the global performance of the solution algorithm. Computational results on benchmark datasets are provided to support this analysis, and guide the selection of the most promising methods to generate these sequences.

2014

Circle covering representation for nesting problems with continuous rotations

Authors
Rocha, P; Rodrigues, R; Gomes, AM; Toledo, FMB; Andretta, M;

Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)

Abstract
This paper analyses distinct methods to represent a polygon through circle covering, which satisfy specific requirements, that impact primarily the feasibility and the quality of the layout of final solution. The trade-off between the quality of the polygonal representation and its derived number of circles is also discussed, showing the impact on the resolution of the problem, in terms of computational efficiency. The approach used to tackle the Nesting problem in strip packing uses a Non-Linear Programming model. Addressing these problems allows to tackle real world problems with continuous rotations. © IFAC.

2013

Circle covering using medial axis

Authors
Rocha, P; Rodrigues, R; Toledo, FMB; Gomes, AM;

Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)

Abstract
A good representation of a simple polygon, with a desired degree of approximation and complexity, is critical in many applications. This paper presents a method to achieve a complete Circle Covering Representation of a simple polygon, through a topological skeleton, the Medial Axis. The aim is to produce an efficient circle representation of irregular pieces, while considering the approximation error and the resulting complexity, i.e. the number of circles. This will help to address limitations of current approaches to some problems, such as Irregular Placement problems, which will, in turn, provide a positive economic and environmental impact where similar problems arise. © 2013 IFAC.