Instance Created:  September 19, 2001
Number of Cities:  4,663
Optimal Value:  1,290,319
Solved:  March 23, 2002
Solution Method:  Concorde -C 24, QSopt LP solver, LKH+tmerge tour
Solution Time:  560,951 seconds, AMD Athlon 1900+

History

Date	Gap	Lower Bound	Tour
3.18.02			1,290,323 - Found by merging 10 LKH (each with n trials). The 10 LKH runs took a total of 17,183 seconds on an AMD Athlon 1900+ processor, and the merge took an additional 0.20 seconds. The best of the LKH tours had length 1,290,334.
3.27.02	Optimal	1,290,319 - Concorde -C 24, starting with a 1,290,334 upper bound, using QSopt as an LP solver. The run was carried out on a single AMD Althlon 1900+ processor (1.6 GHz), in 560,951 seconds.	1,290,319 - Found during branching run by Lin-Kernighan heuristic.

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.

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