Instance Created:  May 6, 2002
Number of Cities:  238025
Status:  OPEN
Best Tour:  578,761
Best Lower Bound:  xxx

History

Date	Gap	Lower Bound	Tour
12.08.02			579,075 - Found by Keld Helsgaun using variants of his LKH code.
3.21.03			579,045 - Found by Hung Dinh Nguyen using a hybrid genetic algorithm, starting with the above tour.
9.12.04			578,865 - Found by Keld Helsgaun using variants of his LKH code.
7.4.08			578,828 - Found by Keld Helsgaun using variants of his LKH code.
19.7.08			578,827 - Found by Changxing Dong, Gerold Jaeger, Paul Molitor, Dirk Richter on an AMD Opteron 2,6 GHz by a variant of LKH.
05.08.08			578,821 - Found by Changxing Dong, Gerold Jaeger, Paul Molitor, Dirk Richter on an AMD Opteron 2,6 GHz by a variant of LKH.
07.08.08			578,813 - Found by Keld Helsgaun using variants of his LKH code.
14.08.08			578,808 - Found by Changxing Dong, Gerold Jaeger, Paul Molitor, Dirk Richter on an AMD Opteron 2,6 GHz by a variant of LKH.
29.08.08			578,808 - Found by Changxing Dong and Paul Molitor using LKH with Karp partitioning.
17.10.08			578,786 - Found by Keld Helsgaun using parallel versions of his LKH code.
20.10.08			578,783 - Found by Changxing Dong and Paul Molitor using LKH with Karp partitioning.
17.10.08			578,782 - Found by Keld Helsgaun using a parallel version of his LKH2 code on a 16-processor system.
07.01.09			578,781 - Found by Keld Helsgaun using a version of his LKH2 code.
05.02.09			578,775 - Found by Keld Helsgaun using a version of his LKH2 code.
09.11.12			578,767 - Found by Keld Helsgaun using a parallel version of his LKH2 code.
14.11.12			578,761 - Found by Xavier Clarist.

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.

Last Updated:  November 14, 2012