27/28 August 2014. Several new best solutions and lowerbounds were submitted by Simon Kristiansen, Matias Sørensen, and Thomas R. Stidsen. See XHSTT-2014 with last best either 27/28 August 2014 for these solutions. Note that for 11 of the 25 instances in XHSTT-2014 improved solutions were submitted in August 2014!
22 August 2014. New best solutions to Brazil Instance 6 and Italy Instance 4 were submitted by Árton Dorneles. The solution to Brazil Instance 6 with cost 35 is reported to by optimal.
22 August 2014. New best solutions to Falkonergaardens Gymnasium 2012, Vejen Gymnasium 2009, and Westside 2009 were submitted by Jeffrey H. Kingston.
16/18 August 2014. New best solutions to Netherlands Kottenpark2003 and Hasseris Gymnasium 2012 were submitted by Jeffrey H. Kingston.
8/11 July 2014. New best solutions to Netherlands Kottenpark2003 were submitted by Jeffrey H. Kingston.
28/30 June 2014. New best solutions to Australia TES99 and Netherlands Kottenpark2003 were submitted by Jeffrey H. Kingston.
1/6/7 May 2014. New best solutions to Australia SAHS96 and Italy Instance4 were submitted by Jeffrey H. Kingston.
April 26, 2014. A new best solution to Western Greece University Instance4 was submitted by Ioannis Tassopoulos and Grigorios Beligiannis.
March 17, 2014. The archives XHSTT-2014 and XHSTT-2014A were created, containing instances that use the simplified cost functions. On the way several functional improvements were executed, hence the old archives are obsolete in this sense as well.
10/20/27 February, 12/13 March 2014. New best solutions to Australia BGHS98 and Italy Instance4 were submitted by Jeffrey H. Kingston.
January 2014. The dataset Westside2009 was contribruted by Luke Muggy and Todd Easton.
January 2014. The archives XHSTT-2013 and "ALL_INSTANCES" are updated, correcting some small issues. Please update your local files.
December 2013. New best solutions to Brazil Instance 3 and Brazil Instance 4 were submitted by Matias Sørensen. Brazil Instance 4 is now claimed to be solved to optimality.
October 2013. New best solutions to Brazil Instance 5 and Brazil Instance 7 were submitted by Árton Dorneles.
September 2013. Several new best solutions have been provided by Simon Kristiansen, Matias Sørensen, and Thomas R. Stidsen. These solutions are added to the datasets, see for example Brazil Instance1. They also reported several lowerbounds to solutions, which also have been added. For example the solution with objective value 38 for Brazil Instance1 is (reported to be) optimal.
March 2013. The archive XHSTT-2013 is put online. It consists of instances used in ITC2011, though several instances have been corrected. Consequently the archives XHSTT-ITC2011 and XHSTT-ITC2011-hidden are outdated.
December 2012. There is a new constraint type available, the OrderEventsConstraint. It describes which events should follow each other and between which time bounds.
August 2012. From October 2011 to June 2012 the Third International Timetabling Competition (ITC 2011) was running. It was devoted to high school timetabling, and used the archives and datasets in the format XHSTT on these pages.
