Instance Created:  May 6, 2002
Number of Cities:  744710
Status:  OPEN
Best Tour:  1,611,232
Best Lower Bound:  xxx

History

Date	Gap	Lower Bound	Tour
12.08.02			1,612,132 - Found by Keld Helsgaun using variants of his LKH code.
21.03.03			1,612,036 - Found by Hung Dinh Nguyen using a hybrid genetic algorithm, starting with the above tour.
09.12.04			1,611,547 - Found by Keld Helsgaun using variants of his LKH code.
25.04.06			1,611,534 - Found by Keld Helsgaun using variants of his LKH code.
30.07.08			1,611,399 - Found by Keld Helsgaun using variants of his LKH code.
04.09.08			1,611,397 - Found by C. Dong and P. Molitor, using LKH with Karp partitioning (working further on points near to the borders of the partition).
24.09.08			1,611,394 - Found by Keld Helsgaun using variants of his LKH code.
04.29.08			1,611,386 - Found by C. Dong and P. Molitor, using LKH with Karp partitioning (working further on points near to the borders of the partition).
13.10.08			1,611,288 - Found by Keld Helsgaun using parallel versions of his LKH code.
19.12.08			1,611,278 - Found by Keld Helsgaun using parallel versions of his LKH2 code.
06.01.09			1,611,277 - Found by Keld Helsgaun using parallel versions of his LKH2 code.
26.02.09			1,611,276 - Found by Keld Helsgaun using parallel versions of his LKH2 code.
09.11.12			1,611,270 - Found by Keld Helsgaun using parallel versions of his LKH2 code.
17.02.13			1,611,246 - Found by Xavier Clarist using a hybrid of local-search methods and a genetic algorithm.
25.06.13			1,611,234 - Found by Xavier Clarist using a hybrid of local-search methods and a genetic algorithm.
18.02.15			1,611,233 - Found by Xavier Clarist using a hybrid of local-search methods and a genetic algorithm.
16.02.17			1,611,232 - Found by Xavier Clarist using a hybrid of local-search methods and a genetic algorithm.

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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