Instance Created:  April 26, 2002
Number of Cities:  19289
Status:  OPEN
Best Tour:  55798
Best Lower Bound:  55791

History

Date	Gap	Lower Bound	Tour
10.6.02			55809 - Best of 10 runs of LKH, each with n trials. Total running time 309264 seconds on an AMD Althlon 1900+ processor (1.6 GHz).
2.2.03			55804 - Found by Keld Helsgaun, using a variant of LKH.
16.3.03			55803 - Found by Hung Dinh Nguyen using a parallel hybrid genetic algorithm.
7.7.04			55801 - Found by Keld Helsgaun, using a variant of LKH.
22.10.06			55799 - Found by Boris Goldengorin, Gerold Jaeger, Paul Molitor, Dirk Richter by a tolerance-based variant of LKH using Weixiong Zhang's idea of backbones. The running time was 176578 seconds on a Intel Xeon 2.4 Ghz with 1GB RAM.
15.5.07			55798 - Found by Keld Helsgaun, using LKH 2.
26.4.17	0.013%	55791 - Concorde (-Z1 -J4), using CPLEX as an LP solver. Wall-clock time for the branch-and-cut search was 2.9 days on a 48-core Intel Xeon E5-2620 @ 2.00GHz cluster; search tree contained 3,197 nodes.

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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