String constraint solving refers to solving combinatorial problems involving constraints over string variables. String solving approaches have become popular over the past few years given the massive use of strings in...
详细信息
String constraint solving refers to solving combinatorial problems involving constraints over string variables. String solving approaches have become popular over the past few years given the massive use of strings in different application domains like formal analysis, automated testing, database query processing, and cybersecurity. This article reports a comprehensive survey on string constraint solving by exploring the large number of approaches that have been proposed over the past few decades to solve string constraints.
This article addresses the Flexible Job Shop Scheduling and Lot Streaming Problem (FJSSP-LS) under setup and transport resource constraints. While the related literature emphasises the lot streaming policy for time-ba...
详细信息
This article addresses the Flexible Job Shop Scheduling and Lot Streaming Problem (FJSSP-LS) under setup and transport resource constraints. While the related literature emphasises the lot streaming policy for time-based objectives, setup and transport resource constraints were not considered simultaneously with this policy, limiting the resulting schedule's applicability in practice. For this reason, we propose a novel constraint programming (CP) model enriched by an efficient variable and value ordering strategy specifically designed for the FJSSP-LS with resource constraints. We also present a CP-based iterative improvement method, CP-based Large Neighbourhood Search (CP-based LNS), that focuses on exploring large neighbourhoods through the CP model. Both models are initially tested for the FJSSP and have been shown to provide the best solutions to well-known benchmark instances. Next, they are used for the FJSSP-LS, and the proposed CP-based LNS improves the objective function value by 4.68 percent on average compared to the CP model for the generated test problems.
A hybrid flow shop group scheduling problem (HFGSP) involves two distinct sub-problems, the arrangement of groups and the configuration of jobs within each group. Constructing its mathematical model based on the class...
详细信息
A hybrid flow shop group scheduling problem (HFGSP) involves two distinct sub-problems, the arrangement of groups and the configuration of jobs within each group. Constructing its mathematical model based on the classification of these sub-problems can help better understand the problem's characteristics. However, the existing literature fails to establish MILP models of HFGSP based on the interrelation between each subproblem and the respective process constraints satisfied by each subproblem. To address this gap, our study first categorizes all the constraints in the HFGSP according to several factors: group arrangement, job arrangement within the group, process requirements between groups, process requirements between jobs from the same group, process requirements between adjacent stages, and the relationship between the decision variables of completion time and the objective constraint. Following this classification, we construct 48 available MILP models of HFGSP. Additionally, we also propose an efficient constraint programming (CP) model of HFGSP. Numerous experiments are conducted to verify the correctness and performance of all 48 MILP models across different test instances, analyze the complexities of all models, and excavate their intrinsic characteristics. Through our evaluation for the 48 models, we observe that models 24 and 48 exhibit superior performance. This highlights the effectiveness of the hybrid modeling approach, which synergistically combines sequence-based modeling for groups and position-based adjacent modeling for jobs within each group. The utilization of this hybrid modeling approach enables the construction of high-quality MILP models for addressing the HFGSP problem. Our intention is to bridge the gap between MILP modeling of HFGSP and problem-specific algorithms, thereby providing a comprehensive understanding of the problem and offering potential solutions.
Routing and Spectrum Allocation (RSA) is one of the central problems in modern optical networks. In this setting, also called Flexible Grid, we want to find paths and allocate non-overlapping frequency slots for as ma...
详细信息
The research objective is to support the maintenance unit with route planning prior to performing road inspection, the model is based on VRP problem settings, and with the addition of compulsory road sections and allo...
详细信息
ISBN:
(纸本)9783037857762
The research objective is to support the maintenance unit with route planning prior to performing road inspection, the model is based on VRP problem settings, and with the addition of compulsory road sections and allowing shortcuts through small pathways during the inspection to reduce time consumption. By employing constraint programming (CP) technology and optimization solution mechanism to construct inspection scheduling model, and the objective is to minimize time consumption of the road inspection. The province and county roads in Douliou city are chosen as examples for analysis, plans out best routes for inspection process, and also displays all the road sections passed by inspection vehicle. Thus this model can be used as reference to support the authorities to efficiently allocate resources for the inspection process, and achieve the objective as shorten the inspection time consumption.
Scheduling frameworks are not necessarily stable. The aim is to introduce schedules resistant to disruptions such as when resources become unavailable, the supply chain for them breaks down, etc. A schedule is robust ...
详细信息
Scheduling frameworks are not necessarily stable. The aim is to introduce schedules resistant to disruptions such as when resources become unavailable, the supply chain for them breaks down, etc. A schedule is robust if it absorbs some level of unforeseen events when at most a certain number of activities are delayed. Taking advantage of constraint programming, we present two new filtering algorithms for a constraint that models cumulative scheduling problems in robust contexts where up to r out of n tasks can be concurrently delayed while keeping the schedule valid. We adapt the overload-checking and edge-finding filtering rules for this framework. We show that our robust versions of these algorithms run in & UTheta;(r2nlog(n)) and O(r2znlog(n)), respectively, where z denotes the number of distinct capacities of all tasks. This achievement implies that the complexities of the state-of-the-art algorithms for these techniques are invariable when r is constant. Experiments illustrate that our algorithms scale, with respect to n and r. As a practical application, the experimental results on a special case of crane assignment problem also verify a stronger filtering for these methods in terms of backtrack numbers as well as computation times when used in conjunction with time tabling. Finally, in order to show that our CP-based algorithms improve to solve a robust scheduling problem, we make a comparison against temporal protection as an external robust scheduling approach.
We present a domain for string decision variables of bounded length, combining features from fixed-length and unbounded-length string solvers to reason on an interval defined by languages of prefixes and suffixes. We ...
详细信息
ISBN:
(纸本)9781479929719
We present a domain for string decision variables of bounded length, combining features from fixed-length and unbounded-length string solvers to reason on an interval defined by languages of prefixes and suffixes. We provide a theoretical groundwork for constraint solving on this domain and describe propagation techniques for several common constraints.
The Job Shop Scheduling Problem (JSSP) is a well-known optimization problem in manufacturing, where the goal is to determine the optimal sequence of jobs across different machines to minimize a given objective. In thi...
详细信息
Trains have a constrained schedule and are not available on demand. If a malfunction is detected, the moment and the place to fix the problem, while keeping the network at its optimal use, may not be easy to find, giv...
详细信息
This document represents the proceedings of the 2024 XCSP3 Competition. The results of this competition of constraint solvers were presented at CP'24 (30th International Conference on Principles and Practice of Co...
详细信息
暂无评论