Instance Created:  April 26, 2002
Number of Cities:  7454
Optimal Value:  19535
Solved:  April 5, 2017

History

Date	Gap	Lower Bound	Tour
10.6.02			19538 - Best of 10 runs of LKH, each with n trials. Total running time 28597 seconds on an AMD Althlon 1900+ processor (1.6 GHz).
2.2.03			19535 - Found by Keld Helsgaun, using a variant of LKH.
4.5.17	Optimal	19535 - Concorde -Z1 -J4 (with domino-parity inequalities). Run on a network of four machines, each with two 6-core Intel Xeon E5-2620 @ 2.00GHz processors. Wall clock time 5 hours, 53 minutes (for branch-and-cut search)

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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