Instance Created:  July 29, 2001
Number of Cities:  7,146
Status:  OPEN
Best Tour:  172,386
Best Lower Bound:  172,350

History

Date	Gap	Lower Bound	Tour
8.12.01	0.098%	172,350 - Concorde -C 20, with Cplex 6.5 LP solver, 124 hours, 500 MHz EV6 Alpha, the branch-and-cut run created a search tree with 431 nodes.	172,519 - found by a call to linkern during Concorde's branch-and-cut run
8.14.01	0.021%		172,387 - found by running linkerh to produce 10 tours, and then merging the tours using tmerge. The 10 linkerh runs took a total of 46,249 seconds on a 500 MHz EV6 Alpha and the tmerge run took an additional 49.45 seconds. The best of the linerh tours had length 172,396.
5.3.03	0.021%		172,386 - found by Keld Helsgaun running a variant of his LKH code.

Notes

1. Concorde is our linear-programming based TSP solver.

2. linkern is an implementation of Martin, Otto, and Felten's Chained Lin-Kernighan heuristic. It is included in the Concorde code.

3. LKH is Keld Helsgaun's powerful implementation of the Lin-Kernighan heuristic.
4. linkerh is an implementation of the Lin-Kernighan heuristic, making use of a number of the ideas introduced in Keld Helsgaun's LKH code.

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