4,395 research outputs found
Operations research methods in compiler backends
Operations research can be defined as the theory of numerically
solving decision problems. In this context, dealing with optimization
problems is a central issue. Code generation is performed by the backend phase of a compiler, a program which transforms the source code of an application into optimized machine code. Basically, code generation is an optimization problem, which can be modelled in a way similar to typical problems in the area of operations research. In this article, that similarity is demonstrated by opposing integer linear programming models for problems of the operations research and of code generation. The time frame for solving the generated integer linear programs (ILPs) as a part of the compilation process is small. As a consequence, using well-structured ILP-formulations and ILP-based approximations is necessary. The second part of the paper will give a brief survey on guidelines and techniques for both issues
Scheduling Bidirectional Traffic on a Path
We study the fundamental problem of scheduling bidirectional traffic along a
path composed of multiple segments. The main feature of the problem is that
jobs traveling in the same direction can be scheduled in quick succession on a
segment, while jobs in opposing directions cannot cross a segment at the same
time. We show that this tradeoff makes the problem significantly harder than
the related flow shop problem, by proving that it is NP-hard even for identical
jobs. We complement this result with a PTAS for a single segment and
non-identical jobs. If we allow some pairs of jobs traveling in different
directions to cross a segment concurrently, the problem becomes APX-hard even
on a single segment and with identical jobs. We give polynomial algorithms for
the setting with restricted compatibilities between jobs on a single and any
constant number of segments, respectively
Algorithms for Scheduling Problems
This edited book presents new results in the area of algorithm development for different types of scheduling problems. In eleven chapters, algorithms for single machine problems, flow-shop and job-shop scheduling problems (including their hybrid (flexible) variants), the resource-constrained project scheduling problem, scheduling problems in complex manufacturing systems and supply chains, and workflow scheduling problems are given. The chapters address such subjects as insertion heuristics for energy-efficient scheduling, the re-scheduling of train traffic in real time, control algorithms for short-term scheduling in manufacturing systems, bi-objective optimization of tortilla production, scheduling problems with uncertain (interval) processing times, workflow scheduling for digital signal processor (DSP) clusters, and many more
Advances and Novel Approaches in Discrete Optimization
Discrete optimization is an important area of Applied Mathematics with a broad spectrum of applications in many fields. This book results from a Special Issue in the journal Mathematics entitled ‘Advances and Novel Approaches in Discrete Optimization’. It contains 17 articles covering a broad spectrum of subjects which have been selected from 43 submitted papers after a thorough refereeing process. Among other topics, it includes seven articles dealing with scheduling problems, e.g., online scheduling, batching, dual and inverse scheduling problems, or uncertain scheduling problems. Other subjects are graphs and applications, evacuation planning, the max-cut problem, capacitated lot-sizing, and packing algorithms
Restricted assignment scheduling with resource constraints
We consider parallel machine scheduling with job assignment restrictions, i.e., each job can only be processed on a certain subset of the machines. Moreover, each job requires a set of renewable resources. Any resource can be used by only one job at any time. The objective is to minimize the makespan. We present approximation algorithms with constant worst-case bound in the case that each job requires only a fixed number of resources. For some special cases optimal algorithms with polynomial running time are given. If any job requires at most one resource and the number of machines is fixed, we give a PTAS. On the other hand we prove that the problem is APX-hard, even when there are just three machines and the input is restricted to unit-time jobs. (C) 2018 Published by Elsevier B.V
Bütünleşik tedarik zinciri çizelgeleme modelleri: Bir literatür taraması
Research on integration of supply chain and scheduling is relatively recent, and
number of studies on this topic is increasing. This study provides a comprehensive
literature survey about Integrated Supply Chain Scheduling (ISCS) models to help
identify deficiencies in this area. For this purpose, it is thought that this study will
contribute in terms of guiding researchers working in this field. In this study,
existing literature on ISCS problems are reviewed and summarized by introducing
the new classification scheme. The studies were categorized by considering the
features such as the number of customers (single or multiple), product lifespan
(limited or unlimited), order sizes (equal or general), vehicle characteristics
(limited/sufficient and homogeneous/heterogeneous), machine configurations and
number of objective function (single or multi objective). In addition, properties of
mathematical models applied for problems and solution approaches are also
discussed.Bütünleşik Tedarik Zinciri Çizelgeleme (BTZÇ) üzerine yapılan araştırmalar
nispeten yenidir ve bu konu üzerine yapılan çalışma sayısı artmaktadır. Bu çalışma,
bu alandaki eksiklikleri tespit etmeye yardımcı olmak için BTZÇ modelleri hakkında
kapsamlı bir literatür araştırması sunmaktadır. Bu amaçla, bu çalışmanın bu alanda
çalışan araştırmacılara rehberlik etmesi açısından katkı sağlayacağı
düşünülmektedir. Bu çalışmada, BTZÇ problemleri üzerine mevcut literatür gözden
geçirilmiş ve yeni sınıflandırma şeması tanıtılarak çalışmalar özetlenmiştir.
Çalışmalar; tek veya çoklu müşteri sayısı, sipariş büyüklüğü tipi (eşit veya genel),
ürün ömrü (sınırlı veya sınırsız), araç karakteristikleri (sınırlı/yeterli ve
homojen/heterojen), makine konfigürasyonları ve amaç fonksiyonu sayısı (tek veya
çok amaçlı) gibi özellikler dikkate alınarak kategorize edildi. Ayrıca problemler için
uygulanan matematiksel modellerin özellikleri ve çözüm yaklaşımları da
tartışılmıştır
Parallel machine scheduling with release dates, due dates and family setup times
In manufacturing, there is a fundamental conflict between efficient production and delivery performance. Maximizing machine utilization by batching similar jobs may lead to poor delivery performance. Minimizing customers' dissatisfaction may lead to an inefficient use of the machines. In this paper, we consider the problem of scheduling n independent jobs with release dates, due dates, and family setup times on m parallel machines. The objective is to minimize the maximum lateness of any job. We present a branch-and-bound algorithm to solve this problem. This algorithm exploits the fact that an optimal schedule is contained in a specific subset of all feasible schedules. For lower bounding purposes, we see setup times as setup jobs with release dates, due dates and processing times. We present two lower bounds for the problem with setup jobs, one of which proceeds by allowing preemption
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