scholarly journals Lexicographically Maximum Contraflow Problem with Vertex Capacities

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Phanindra Prasad Bhandari ◽  
Shree Ram Khadka
Keyword(s):  
Road Network ◽  
Maximum Flow ◽  
Evacuation Planning ◽  
Planning Problem ◽  
Solution Algorithms ◽  
Computational Performance ◽  
Speed Up ◽  
Priority Order ◽  
Vertex Capacities ◽  
Direction Reversal

The contraflow approach has been extensively considered in the literature for modeling evacuations and has been claimed, due to its lane-direction-reversal capability, as an efficient idea to speed up the evacuation process. This paper considers the contraflow evacuation model on network with prioritized capacitated vertices that allows evacuees to be held at intermediate spots too, respecting their capacities and priority order. In particular, it studies the maximum flow evacuation planning problem and proposes polynomial and pseudo-polynomial time solution algorithms for static network and dynamic multinetwork, respectively. A real dataset of Kathmandu road network with evacuation spaces is considered to implement the algorithm designed for dynamic multinetwork and to observe its computational performance.

scholarly journals Efficient Solution Approach to Maximum Flow Evacuation Planning Problem without Flow Conservation Aspect

2018 ◽  
Vol 13 (1) ◽  
pp. 108-116
Author(s):  
Phanindra Prasad Bhandari ◽  
Shree Ram Khadka
Keyword(s):  
Network Flow ◽  
Efficient Solution ◽  
Maximum Flow ◽  
Evacuation Planning ◽  
Planning Problem ◽  
Intermediate Node ◽  
Solution Approach ◽  
Solution Strategies ◽  
Source Sink ◽  
Flow Conservation

 An attempt of shifting as more people as possible and/or their logistics from a dangerous place to a safer place is an evacuation planning problem. Such problems modeled on network have been extensively studied and the various efficient solution procedures have been established. The solution strategies for these problems are based on source-sink path augmentation and the flow function satisfies the flow conservation at each intermediate node. Besides this, the network flow problem in which flow may not be conserved at node necessarily could also be used to model the evacuation planning problem. This paper proposes a model for maximum flow evacuation planning problem on a single-source-single-sink static network with integral arc capacities with holding capability of evacuees in the temporary shelter at intermediate nodes and extends the model into the dynamic case. Journal of the Institute of Engineering, 2017, 13(1): 108-116

scholarly journals Flow Improvement in Evacuation Planning with Budget Constrained Switching Costs

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Ram Chandra Dhungana ◽  
Tanka Nath Dhamala
Keyword(s):  
Network Flow ◽  
Large Scale ◽  
Maximum Flow ◽  
Evacuation Planning ◽  
Solution Technique ◽  
Planning Problem ◽  
Constrained Problems ◽  
Full Capacity ◽  
Evacuation Plan ◽  
Flow Improvement

Many large-scale natural and human-created disasters have drawn the attention of researchers towards the solutions of evacuation planning problems and their applications. The main focus of these solution strategies is to protect the life, property, and their surroundings during the disasters. With limited resources, it is not an easy task to develop a universally accepted model to handle such issues. Among them, the budget-constrained network flow improvement approach plays significant role to evacuate the maximum number of people within the given time horizon. In this paper, we consider an evacuation planning problem that aims to shift a maximum number of evacuees from a danger area to a safe zone in limited time under the budget constraints for network modification. Different flow improvement strategies with respect to fixed switching cost will be investigated, namely, integral, rational, and either to increase the full capacity of an arc or not at all. A solution technique on static network is extended to the dynamic one. Moreover, we introduce the static and dynamic maximum flow problems with lane reversal strategy and also propose efficient algorithms for their solutions. Here, the contraflow approach reverses the direction of arcs with respect to the lane reversal costs to increase the flow value. As an implementation of an evacuation plan may demand a large cost, the solutions proposed here with budget constrained problems play important role in practice.

scholarly journals Non-conserving Flow Aspect of Maximum Dynamic Flow Problem

2018 ◽  
Vol 14 (1) ◽  
pp. 107-114
Author(s):  
Phanindra Prasad Bhandari ◽  
Shree Ram Khadka
Keyword(s):  
Network Flow ◽  
Efficient Solution ◽  
Flow Problem ◽  
Dynamic Network ◽  
Maximum Flow ◽  
Solution Procedure ◽  
Evacuation Planning ◽  
Planning Problem ◽  
Intermediate Node ◽  
Flow Conservation

Shifting as many people as possible from disastrous area to safer area in a minimum time period in an efficient way is an evacuation planning problem (EPP). Modeling the evacuation scenarios reflecting the real world characteristics and investigation of an efficient solution to them have become a crucial due to rapidly increasing number of natural as well as human created disasters. EPPs modeled on network have been extensively studied and the various efficient solution procedures have been established where the flow function satisfies the flow conservation at each intermediate node. Besides this, the network flow problem in which flow may not be conserved at nodes necessarily could also be useful to model the evacuation planning problem. This paper proposes an efficient solution procedure for maximum flow evacuation planning problem of later kind on a single-source-single-sink dynamic network with integral arc capacities with holding capability of flow (evacuees) in the temporary shelter at intermediate nodes. Journal of the Institute of Engineering, 2018, 14(1): 107-114

scholarly journals Maximum Flow Evacuation Planning Problem with Non-Conservation Flow Constraint

2020 ◽  
Vol 10 (1) ◽  
pp. 25-32
Author(s):  
Phanindra Prasad Bhandari ◽  
Shree Ram Khadka
Keyword(s):  
Optimization Model ◽  
Efficient Algorithm ◽  
Time Horizon ◽  
Maximum Flow ◽  
Safe Zone ◽  
Evacuation Planning ◽  
Planning Problem ◽  
Flow Conservation

The optimization model of the maximum flow evacuation planning problem efficiently sends a maximum number of evacuees along with the routes of their transshipment from the disastrous zone, the source, to the safe zone, the sink, over a given time horizon. The limitation of the problem with the flow conservation constraint at the intermediate nodes is that even one more evacuee cannot be sent out from the source, if the evacuee cannot reach the sink. However, evacuators must attempt to send out as many evacuees as possible to safer places despite the sink. There may be relatively safe places in between the source and the sink. The limitation is due to the flow conservation constraint. In this paper, we remodel the problem with non-conservation flow constraint and propose an efficient algorithm. With this approach one can send as many evacuees as in the flow conservation case from the source to the sink. Moreover, a maximum number of evacuees can also be sent to the relatively safe places in between the source and the sink. The routes of their transshipment can also be identified.

scholarly journals A Lower Bound for the Query Phase of Contraction Hierarchies and Hub Labels and a Provably Optimal Instance-Based Schema

Algorithms ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 164
Author(s):  
Tobias Rupp ◽  
Stefan Funke
Keyword(s):  
Lower Bound ◽  
Lower Bounds ◽  
Real World ◽  
Road Network ◽  
Upper And Lower Bounds ◽  
Bounded Degree ◽  
Shortest Path Routing ◽  
Graph Classes ◽  
Speed Up ◽  
To Come

We prove a Ω(n) lower bound on the query time for contraction hierarchies (CH) as well as hub labels, two popular speed-up techniques for shortest path routing. Our construction is based on a graph family not too far from subgraphs that occur in real-world road networks, in particular, it is planar and has a bounded degree. Additionally, we borrow ideas from our lower bound proof to come up with instance-based lower bounds for concrete road network instances of moderate size, reaching up to 96% of an upper bound given by a constructed CH. For a variant of our instance-based schema applied to some special graph classes, we can even show matching upper and lower bounds.

scholarly journals A GPU Accelerated Red-Black SOR Algorithm for Computational Fluid Dynamics Problems

2011 ◽  
Vol 320 ◽  
pp. 335-340 ◽  
Author(s):  
Ji Tang Liu ◽  
Zhao Song Ma ◽  
Shi Hai Li ◽  
Ying Zhao
Keyword(s):  
High Performance ◽  
Memory Allocation ◽  
Compute Unified Device Architecture ◽  
Problem Size ◽  
Benchmark Data ◽  
Device Architecture ◽  
Computational Performance ◽  
Speed Up ◽  
Sequential Code ◽  
Dynamics Problems

GPUs are high performance co-processors of CPU for scientific computing including CFD. We present an optimistic shared memory allocation strategy to solve 2D CFD problems using Red-Black SOR method on GPU with CUDA (Compute Unified Device Architecture). Lid-driven results are compared with the benchmark data. The speed up ratio of same problem size by using NVDIA GTX480 and Intel Core-Dual 3.0GHz processor is discussed, the performance of GPU is 120 times faster than the sequential code on CPU with the problem size of 756756. Based on this work, we conclude that using the memory hierarchy properly has a key role in improving the computational performance of GPU.

scholarly journals Optimization Models and Solution Algorithms for Freight Routing Planning Problem in the Multi-Modal Transportation Networks: A Review of the State-of-the-Art

2015 ◽  
Vol 9 (1) ◽  
pp. 714-723 ◽  
Author(s):  
Yan Sun ◽  
Maoxiang Lang ◽  
Danzhu Wang
Keyword(s):  
Heuristic Algorithms ◽  
Transportation Network ◽  
Algorithm Design ◽  
Global Market ◽  
Optimization Models ◽  
Planning Problem ◽  
Total Production ◽  
Solution Algorithms ◽  
Freight Routing ◽  
A Company

With the remarkable development of international trade, global commodity circulation has grown significantly. To accomplish commodity circulation among various regions and countries, multi-modal transportation scheme has been widely adopted by a large number of companies. Meanwhile, according to the relevant statistics, the international logistics costs reach up to approximate 30-50% of the total production cost of the companies. Lowering the transportation costs has become one of the most important sources for a company to raise profits and maintain competitiveness in the global market. Thus, how to optimize freight routes selection to move commodities through the multi-modal transportation network has gained great concern of both the decision makers of the companies and the multi-modal transport operators. In this study, we present a systematical review on the multi-modal transportation freight routing planning problem from the aspects of model formulation and algorithm design. Following contents are covered in this review: (1) distinguishing the formulation characteristics of various optimization models; (2) identifying the optimization models in recent studies according to the formulation characteristics; and (3) discussing the solution approaches that are developed to solve the optimization models, especially the heuristic algorithms.

scholarly journals Generalized Contraflow for Evacuation Planning Problem

2018 ◽  
Vol 1 (1) ◽  
pp. 38-49
Author(s):  
Urmila Pyakurel
Keyword(s):  
Polynomial Time ◽  
World Wide ◽  
Approximation Scheme ◽  
Evacuation Planning ◽  
Planning Problem ◽  
Polynomial Time Approximation Scheme ◽  
Lossy Networks ◽  
Approximation Solution ◽  
Time Approximation ◽  
Pseudo Polynomial Time

The research in evacuation planning has been very much motivated due to the rapidly increased number of disasters world wide. It supports to remove the evacuees from dangerous areas to safe areas. Contraflow reconfiguration during evacuation make traffic smooth by reversing the required road directions from dangerous areas to safe areas that improve both flow and speed significantly. On lossy network, the generalized maximum dynamic contraflow and generalized earliest arrival contraflow problems have been solved efficiently with pseudo-polynomial time. This paper focuses in analytical solutions on generalized contraflow for evacuation planning problem. The problems are considered on two terminal lossy networks. We solve the generalized maximum static contraflow problem in pseudo-polynomial time and compute its approximation solution in polynomial time. Moreover, we present a fully polynomial time approximation scheme (FPTAS) to compute an approximate generalized maximum dynamic contraflow solution.

scholarly journals An Efficient Satellite Resource Cooperative Scheduling Method on Spatial Information Networks

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3293
Author(s):  
Huilong Fan ◽  
Zhan Yang ◽  
Shimin Wu ◽  
Xi Zhang ◽  
Jun Long ◽  
...  
Keyword(s):  
Graph Theory ◽  
Spatial Information ◽  
Resource Scheduling ◽  
Maximum Flow ◽  
Resource Planning ◽  
Information Networks ◽  
Planning Problem ◽  
Scheduling Problems ◽  
Time Consumption ◽  
Resource Request

To overcome the low timeliness of resource scheduling problems in spatial information networks, we propose a method based on a dynamic reconstruction of resource request queues and the autonomous coordinated scheduling of resources. First, we construct a small satellite network and combine the graph maximum flow theory to solve the link resource planning problem during inter-satellite data transmission. In addition, we design a multi-satellite resource scheduling algorithm with minimal time consumption based on graph theory. The algorithm is based on graph theory to reallocate the resource request queue to satellites with idle processing resources. Finally, we simulate the efficient resource scheduling capability in the spatial information network and empirically compare our approaches against two representative swarm intelligence baseline approaches and show that our approach has significant advantages in terms of performance and time consumption during resource scheduling.

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