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Questions tagged [shortest-path]

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97
votes
6answers
45k views

How do the state-of-the-art pathfinding algorithms for changing graphs (D*, D*-Lite, LPA*, etc) differ?

A lot of pathfinding algorithms have been developed in recent years which can calculate the best path in response to graph changes much faster than A* - what are they, and how do they differ? Are ...
30
votes
0answers
4k views

Combinatorics of Bellman-Ford or how to make cyclic graphs acyclic?

Roughly speaking, my question is: How costly is to make a cyclic graph acyclic while preserving all simple $s$-$t$ paths? Let $K_n$ be a complete undirected graph on vertices $\{0,1,\ldots,n+1\}$. (...
16
votes
0answers
599 views

Lower bounds on single-source shortest paths in directed graphs

Are there any non-trivial lower bounds on the complexity of single-source shortest paths (SSSP) in a directed graph, where all edges have non-negative edge weights? Can we rule out the possibility of ...
13
votes
1answer
9k views

Finding the shortest path in the presence of negative cycles

Given a directed cyclic graph where the weight of each edge may be negative the concept of a "shortest path" only makes sense if there are no negative cycles, and in that case you can apply the ...
12
votes
3answers
1k views

Subgraph containing all nodes and edges that are part of length-limited simple s-t paths in an undirected graph

Quite similar to my previously posted question. This time however, the graph is undirected. Given An undirected graph $G$ with no multiple-edges or loops, A source vertex $s$, A target vertex $t$, ...
11
votes
2answers
671 views

Graph classes for which the diameter can be computed in linear time

Recall the diameter of a graph $G$ is the length of a longest shortest path in $G$. Given a graph, an obvious algorithm for computing $\text{diam}(G)$ solves the all-pairs shortest path problem (APSP) ...
11
votes
1answer
712 views

Identifying useless edges for shortest path

Consider a graph $G$ (the problem makes sense both for directed and undirected graphs). Call $M_G$ the matrix of distances of $G$: $M_G[i, j]$ is the shortest path distance from vertex $i$ to vertex $...
10
votes
3answers
766 views

Shortest distance problem with length as functions of time

Motivation The other day, I was travelling around the city with public transport and I made up an interesting graph problem modelling the problem of finding the shortest-time connection between two ...
8
votes
2answers
472 views

Dijkstra parallelization

I'd like to know what is the best method to parallelize the Dijkstra algorithm. Thanks.
8
votes
1answer
371 views

Motivation for Developing Shortest Path Simplex Algorithms

I'm reading Efficient Shortest Path Simplex Algorithms by Donald Goldfarb, Jianxiu Hao and Shen-Roan Kai who considered "the specialization of the primal simplex algorithm to the problem of finding a ...
8
votes
0answers
110 views

Is APSP verification easier than APSP?

In APSP, the input is an $n$-node directed weighted graph $G$, and the output is an $n \times n$ matrix holding pairwise shortest path distances between nodes in $G$. Define "APSP-Verification" as ...
7
votes
1answer
454 views

Shortest paths perturbation

I have a graph $G=(V,E)$, with positive weights $w_e, e\in E$ on the edges, and I would like to randomly perturb the weights of the edges so that for each pair of distinct vertices $(u,v)$ such that ...
7
votes
3answers
527 views

Preprocessing Sparse, Directed Non-Planar Graphs for Faster Shortest Path

I'm trying to preprocess a very large and sparse directed graph in order to do faster shortest path searches. The vertices have no natural distance function, and the edges are unweighted. One ...
7
votes
2answers
282 views

Ref question: K-nearest neighbours in a graph

Given an undirected graph $G$ with $n$ vertices, $m$ edges, and positive weights on the edges, I am interested in the problem of computing for each vertex the $k$ distinct vertices in $G$ that are ...
6
votes
2answers
5k views

Finding a minimum “node” weight path

Suppose a graph with node weights only (no edge weights). For a given source-sink pair, how can I find a path with the minimal sum of node weights? Does this problem have a name? Is it possible to ...
5
votes
2answers
2k views

Shortest path hitting a given vertex

I believe this problem to be NP-Complete, but I'm unable to find any references on possible reductions. Given a weighted graph (either undirected or directed, I cannot find results for either but am ...
5
votes
2answers
1k views

In a resistor network, is there any relation between the shortest path and the maximum electric current path?

Consider a shortest path problem between the source $s$ and sink $t$ in an undirected weighted graph. There's a well known algorithm such as Dijkstra's algorithm that solves this problem. Naturally, ...
4
votes
2answers
254 views

Shortest distance/path between two households

If you wanted to know the shortest distance/path between two household addresses, which data structure(s) would you use to return the answer efficiently? Say you are considering the set of all ...
4
votes
1answer
255 views

For which values of $k$ is minimum length undirected $k$-disjoint-paths in $\mathcal{P}$?

In a related question, Saeed and Super8 have mentioned the Robertson-Seymour theory which enables us to find $k$ disjoint paths between pairs of vertices $\{s_i,t_i\}_{i=1}^k$ in poly time for fixed $...
4
votes
2answers
2k views

Finding the two shortest paths while minimizing the number of nearby/common edges

The shortest path problem between 2 arbitrary nodes is one that has been covered extensively and the solution is well-known. Consider the edge costs to be arbitrary. Consider the following variant: ...
4
votes
1answer
329 views

Dynamic all-pairs shortest paths - O(1) query

I'm trying to come up with an algorithm to solve all-pairs shortest paths (APSP) problem in dynamic directed planar graph with nonnegative real weights. Additionally: My primary focus is to achieve ...
4
votes
1answer
442 views

Minimum Union-Sum Cost Path

I have a minimum cost path selection problem that is different from the usual shortest path in that each type of cost is accounted only once in the total cost of the path if multiple edges on the path ...
4
votes
1answer
83 views

Cooperative Pathfinding to minimize global costs

There are some algorithms and methods around, that allow cooperative pathfinding. Unfortunately they all seem to aim at avoiding collisions or conflicts between entities. I'm looking for an algorithm ...
4
votes
1answer
159 views

Max Sum Product Multi-objective Shortest path problem

Is anything known about the following problem: I am given a graph. Each edge is labelled by a vector of numbers, called weights. They are numbers between 0 and 1. A path is first assigned a vector, ...
4
votes
0answers
912 views

Path finding algorithm to maximise points of interest along the route

I am trying to write an algorithm to find a path (not the shortest one) between a given start and end point. An user will enter the start location, the end location and the available time to travel. ...
4
votes
0answers
423 views

Dynamic shortest path data structure for DAG

Let $G$ be a dynamic DAG (directed acyclic graph) where new vertices and new edges can be inserted. I am looking for an efficient data structure/algorithm to maintain the shortest path from a fixed ...
4
votes
0answers
570 views

What about apply maxplus algebra for all-pairs shortest paths?

I didn't find deep informations on Wikipedia about all-pairs shortest path, in particular I do not know what is the best algorithm to solve this problem beyond Floyd-Warshall's one, then I do not know ...
3
votes
1answer
206 views

Minimum offset while measuring TSP paths

I have Euclidean graph: each vertex is a point on the 2D plane, so the weight of each edge is the Euclidean distance between the vertices. I am trying to solve TSP with brute algorithm, and I want to ...
3
votes
2answers
3k views

How to solve the Shortest Hamiltonian Path problem on Sparse Graphs?

Problem: Given a positive-weighted undirected graph, find the shortest path (in terms of total sum of edges) that visits each node exactly once. For a subset $S$ of nodes and a node $i\in S$, let $D[...
3
votes
1answer
501 views

Breadth first search and Eppstein K shortest paths algorithm

I'm trying to understand the algorithm for finding K shortest paths in a graph described by Eppstein in this paper: http://www.ics.uci.edu/~eppstein/pubs/Epp-SJC-98.pdf I have trouble particularly ...
3
votes
1answer
143 views

Finding shortest path while maximizing the number of overlapping edges

The shortest path problem between 2 arbitrary nodes is one that has been covered extensively and the solution is well-known. Consider the edge costs to be arbitrary. Consider the following variant: ...
3
votes
1answer
268 views

What exactly is Lawler's modification to Yen's algorithm and how does it work?

I recently read about Yen's algorithm, I understand the algorithm and it seems correct, however Wikipedia mentions that there exists "Lawler's modification" to the algorithm, which is described as ...
3
votes
1answer
152 views

Anyone recognize this as a special type of multi-commodity flow problem?

Consider this problem: $$ \begin{align} \min_{y,z,l \geq 0} \quad & g(y,z,l) := \sum_{(i,j)\in E} \sum_p (-w_{ijp}) y_{ijp} & \\ \textrm{s.t.} \quad & \left( \sum_{(i,j)\in E} y_{ijp} + ...
3
votes
1answer
163 views

Assigning edge weights under shortest path constraints

We are given a graph $G = (V,E)$ and we need to find an assignment of non-negative edge weights (You must give every edge a non-negative weight). We are also given a set $R\subseteq V$ and mapping $c_{...
3
votes
0answers
154 views

Multi-Agent Pathfinding

Quoting from Wang and Botea 2011: An instance is characterized by a graph representation of a map, and a non-empty collection of mobile units $U$. Units are homogeneous in speed and size. Each unit ...
3
votes
0answers
624 views

A constrained shortest path problem. What is the complexity?

I've got the following problem: Consider a graph $G=(V,E)$ with $V=\{v_1,\ldots,v_n\}$, and edge-set $E=\{e_1,\ldots,e_m\}$, with associated costs $c_1,\ldots,c_m$. The problem is to find the ...
2
votes
1answer
74 views

Constant Width Max Sum Product Multi-objective Shortest path problem

This question is a follow-up on the question I asked three days ago here. For convenience I restate it here. I am given a graph. Each edge is labelled by a vector of numbers, called weights. They ...
2
votes
1answer
309 views

Do you know a shortest path algorithm for weighted graphs with hard time windows on the edges and waiting allowed?

Title says it all. I have a weighted Graph G={V,E,ETW} where V is the node set, E the edge set and ETW is a set of edge time windows. A edge time window is a 3-Tuple (edge, starttime, endtime) with ...
2
votes
1answer
432 views

Maximum difference between two shortest paths

My problem is the following maximization problem: Given: A graph $G=(V,E)$, lower bounds $l \in \{0,1,..,K\}^E$ and upper bound $u \in \{0,1,..,K\}^E$ for the edge weights, a source $s$ and two ...
2
votes
1answer
246 views

What is the proof that visibility graphs can be used to compute the shortest path?

I am trying to understand what the proof is that constructing a visibility graph and searching on can give you the shortest path between two points, avoiding a set of convex polygons. I am trying ...
2
votes
1answer
587 views

Highway dimension

I'm interested in understanding some recent theoretical results on pathfinding. Specifically this paper: http://research.microsoft.com/apps/pubs/default.aspx?id=201061 I understand from the paper ...
2
votes
2answers
378 views

Why is label pruning possible with hub labeling?

Hub labeling (HL) computes superlabels using the vertices visited by the forward and reverse Contraction Hierarchies (CH) search. Those labels are then pruned (see HL, sec. 4.2) to generate strict ...
2
votes
1answer
2k views

Shortest simple path with minimum edge cost minus node reward

I have a directed graph which has cycles. Each edge has a nonnegative weight and each vertex has a nonnegative reward. Given two vertices s and t, I need to find a simple path (a path with no ...
2
votes
0answers
483 views

Path finding on graph with state dependent edge costs

I'm looking for a version of path planning that is able to find paths in a graph where edge costs depend on the state of the moving entity. In such cases, it is required to also consider trade-offs, i....
2
votes
0answers
521 views

Shortest non-crossing geometric paths

I have a plane graph $G$ and a set of $k$ vertex pairs $\{s_1,t_1\}, \dots, \{s_k, t_k\}$. The goal is to find $k$ non-crossing paths connecting the pairs of terminals $s_i$ with $t_i$ in the graph so ...
1
vote
1answer
2k views

Run Dijkstra's algorithm twice to detect negative-weight cycles?

Dijkstra's algo (for finding single-source shortest path) assumes that once a vertex has been chosen for expansion (aka exploration), its shortest path has been found. This can only be true if there ...
1
vote
1answer
165 views

Are there any heuristics that works solely on graphs?

I'm exploring heuristics in A* and apparently all heuristics require coordinates of all the locations to calculate a h-cost. This is fine if you are working on grids, but what if you need to work ...
1
vote
1answer
994 views

directed or bidirected in relation to mssp (Multiple source shortest path)

Firstly I wanted to ask. If I have a undirected graph and split all the edges into two directed edges is it still called directed or does it become bi-directed? The main question is i have a graph ...
1
vote
1answer
122 views

K-fold Traveling salesman problem - A variant of TSP

Consider a weighted graph $K_n$ and where the weights between vertices $i,j$ is $w_{ij}$. Consider a path, $\sigma$, passing through each vertex only once. Here $\sigma_i$ is the vertex in the $(i\%n)^...
1
vote
0answers
73 views

multi-agent pickup and delivery algorithm and conflict resolution

I am looking for a pathfinding algorithm handling the following issues: multiple agents the computed paths for agents may not lead to collisions or deadlocks in space-time a stream of activities ...