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26 views

Are there any examples of "autonomous" TSP heuristics

By "autonomous" TSP heuristic I mean algorithms whose reported edge-set for a short Hamilton cycle is invariant under the addition of vertex weights; the terminology is borrowed from differential equa …
Manfred Weis's user avatar
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1 vote

Characterization of greedy TSPs?

A simple "a posteriori" criterion is that on the optimal tour the distances to the tour-neighbors is smaller than that to any of the other vertices. Convexity alone doesn't suffice as the example of e …
Manfred Weis's user avatar
  • 13.2k
3 votes
1 answer
158 views

Fastest algorithm for calculating optimal tours in weighted $K_5$

Weighted $K_5$ have the unique property that their edge set can be interpreted as the disjoint union of their shortest and their longest Hamilton cycle. That makes $K_5$ attractive for designing new T …
Manfred Weis's user avatar
  • 13.2k
1 vote
0 answers
33 views

How to chose the start vector for the MTZ variables

In the context of LP-formulations for the Traveling Salesman Problem the MTZ constraints prevent subtours via $n$ (i.e. effectively $n-1$) additional variables $$u_1=1\\2\le u_2,\,\dots ,\,u_n\le n\\ …
Manfred Weis's user avatar
  • 13.2k
1 vote
1 answer
80 views

Do we really need degree constraints for ILP formulations of TSP problems

The Dantzig-Fulkerson ILP-formulation of the symmetric TSP is $$\min\sum\limits_{i=1}^{n-1}\sum\limits_{j=i+1}^n c_{ij}x_{\lbrace i,j\rbrace}\quad\text{s.t.}\\ \sum\limits_{j\ne i,\,j=1}^n x_{\lbrace …
Manfred Weis's user avatar
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-2 votes
2 answers
146 views

Greedy euclidean tour expansion - a case of unexpected hanging?

In the euclidean plane an common heuristic for the TSP is to start with the convex hull of the point set and then successively integrate as the next point and insertion position the combination that i …
Manfred Weis's user avatar
  • 13.2k
1 vote
0 answers
48 views

Complexity of the TSP for hypercube graphs

Question: what is known about the complexity of finding the Hamilton cycle of minimum weight in graphs that resemble hypercubes with weighted edges?
Manfred Weis's user avatar
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0 votes
0 answers
26 views

Monotony of enforced subtour merging

Is it true that for a symmetric TSP instance in the sequence of edges generated by successively: calculating the optimal 2-factor adding cardinality constraints on the edgesets of the 2-factor's conn …
Manfred Weis's user avatar
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2 votes
1 answer
183 views

Trying to understand "moats"

According to the TSP Gallery moats provide lower bounds for the optimal solution of TSP instances. On the webpage they are depicted as blue rings around red disks, whose radii represent maximal vertex …
Manfred Weis's user avatar
  • 13.2k
-1 votes
1 answer
241 views

Helsgaun's $k$-Opt moves

In his 2009 paper General k-opt submoves for the Lin–Kernighan TSP heuristic, Helsgaun defines the local tour improvements on which the LKH heuristics are based as: with a cycle defined here: which …
Manfred Weis's user avatar
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12 votes
0 answers
221 views

What is known about G. A. Croes

G. A. Croes is the author of the first description of the 2-opt moves heuristic for improving non-optimal traveling salesman tours: Croes, G. A. “A Method for Solving Traveling-Salesman Problems.” Op …
Manfred Weis's user avatar
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4 votes
2 answers
416 views

What Kind of Graph is This?

I am currently developing TSP heuristics that aim at symmetrically reducing the original, complete and undirected graph. The overarching rationale is that the reduction is done via a sequence of regul …
Manfred Weis's user avatar
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0 votes
Accepted

Relation of 1-trees to optimal tours

Just found the answer in the 1969 paper THE TRAVELING-SALESMAN PROBLEM AND MINIMUM SPANNING TREES by Held and Karp; in which it is shown that it is not always possible to find the otimal solution to t …
Manfred Weis's user avatar
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0 votes
1 answer
52 views

Relation of 1-trees to optimal tours

Question: given a complete symmetric graph $G(V,E)$ with $n$ vertices and edges $e_{ij}$ having weight $\omega_{ij}$, does there always exists a vector of vertex potentials $(\pi_1,\,\dots,\,\pi_n)$ t …
Manfred Weis's user avatar
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2 votes
1 answer
139 views

Description of Linear Time Algorithm for TSP in Halin Graphs

I am looking for a description of the linear time algorithm for the TSP in Halin graphs, that was given in "G. Cornuejols, D. Naddef, and W.R. Pulleyblank. Halin graphs and the travelling salesm …
Manfred Weis's user avatar
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