From: janburse@fastmail.fm   
      
   In 1997, Hong Kong judge Wayne Gould saw a partly   
   completed puzzle in a Japanese bookshop. Over six years,   
   he developed a computer program to produce unique   
   puzzles rapidly. The program tries to keep one puzzle   
   ahead of you, by generating the next puzzle while you   
   are solving the present one.   
      
   In the following we show a Prolog program, where   
   the random generation of a Puzzle is performed in   
   less than 2 seconds. The Prolog program was mainly   
   developed for Dogelog Player. We could test the   
   Prolog program also with Prolog systems such as   
   SWI-Prolog, Scryer Prolog and Trealla Prolog.   
      
   The smallest domain first variable ordering heuristic   
   allowed us to solve some hard problems below a minute.   
   Turning the heuristic into a static ordering before   
   search gave us a further boost and the baseline for   
   randomization. Measurement showed that solving blank   
   Sudokus doesn't have a large time variation.   
      
   See also:   
      
   Birthday Paradox and Sudoku Generation   
   https://twitter.com/dogelogch/status/1767714755827908991   
      
   Birthday Paradox and Sudoku Generation   
   https://www.facebook.com/groups/dogelog   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)