Bug me no more, bug!
Sine Nomine Software have released a new version, 1.07, of Wrangler, their popular general mathematical puzzle application.
The previous release of the software, version 1.06, was to remove two puzzles that were subject to a complaint of trademark infringement, and to add a new one in the form of TetraCross, in which the player is presented with four interlocking crosses of four cells each, with nine cells in total, into which the digits from 1 to 9 need to be placed, with the sum of the four cells for each cross totalling the value presented in its centre.
The update to version 1.07 addresses a minor bug in this new puzzle, which is explained in the application’s history document as “Created percentage filled calculation in TetraCross puzzles”.
As usual, the new version can be downloaded straight from Sine Nomine’s website, and will be fully working for registered users, and work as a demo for unregistered users, allowing them to play a limited number of games. Registration costs just £5.
In answer to a question raised after the update to version 1.06, Hiliary Phillips of Sine Nomine Software informs me that Wrangler uses dancing links in the generation of three of its puzzles – Shikaku, Hitori and Binary. SuperDoku, Sine Nomine’s other puzzle software, makes much more extensive use of dancing links, using it to generate almost all of its Sudoku grids. The one exception being the 25×25 grids, which they found were too slow to calculate, and for which they instead use a shuffled preset grid.
Dancing links is a technique proposed by Donald Knuth as an efficient means to implement his Algorithm X, which is in turn a method of solving the exact cover problem – of which Sudoku puzzles are a good example.
