Some thoughts about the sudoku GP 2014

The last tournament of the Sudoku Grand Prix 2014 just ended. I took a satisfying 8th rank in this tournament, which allows me to reach the 15th rank overall. My decision to be an author of a tournament probably cost me a place in the final, to be held in London during the world championship. I took this decision before knowing the major changes of this second edition of the GP - the first edition contained 8 tournaments and only the 6 best results were recorded for the final ranking, this year's ranking is based on 6 best results of 7 tournaments, which leaves no room for error to authors.

I would like to give my views on the changes made to this second edition of the GP:

• New website: this is the most important change. The GP has now its own website, which is very positive. Last year, the GP was in fact a patchwork of tournaments, for the most part already existing (national qualifying,...). This year, the tournaments had the only purpose to serve the GP.
  The website was set up by Karel Tesar (webmaster of Sudokucup) in a short time, we can thank him for his great commitment, he put his skills for the GP. The website is still perfectible, some minor technical problems occurred during some tournaments, but it works well overall. Of course, it's still far from the reference website in this field: logicmastersindia, which has been developped during several years. The establishment of the website has meant that GP organizers have introduced stricter criteria for tournament's authors. Let's talk about these criteria:
• Tournaments duration: Although all durations are possible and feasible, the most common duration for online tournaments is 120 minutes. The majority of GP tournaments last year had this duration (or even 150 minutes). So it was a surprise to see that the organizers decided to reduce this duration to 90 minutes. I don't think it was a bad decision, since these tournaments added to others, densify the agenda and it's not rare to see 2 or 3 online tournaments during some weekends.
• Difficulty: The goal for each tournament was that the best player should be able to submit all puzzles in around 60 minutes. This goal was reached in sudoku tournaments (the time of the winner was always between 49 and 66 minutes), sometimes more on the easy side. - Note that this goal was completely missed in the puzzle tournaments: several tournaments saw no player able to solve all puzzles in the allotted 90 minutes. - I think the decision is not bad. Maybe I would have preferred 70-75 minutes as target time, which would have the effect that players lose less time if they submitted all puzzles with a mistake. But I quite like the idea that the best players have to solve all puzzles, provided that these ones can be solved logically (I will return to this point later).
• Classic oriented: One of the changes this year was the decision to have tournaments with more classic sudokus that online tournaments usually contain. "At least 40% of classic sudoku" were requested from authors. I saw in this decision solely the goal to make the GP more popular, and I'm not sure that simply adding classic sudokus make the tournaments more popular. But I would like to weight this opinion taking into account that on the other side I enjoyed seeing a good amount of classic puzzles on the puzzle competition and it certainly gave me the skinny motivation to participate in all puzzle tournaments. Ideally I wouldn't be against this rule, but I saw two problems there before the start of the competition:
  • Although I don't want to expand on this subject, the presence of classic sudoku in online tournaments will pair with cheaters. I had to downgrade 2 players in my tournament. No comment...
  • Most authors don't like to create classic Sudoku. Having gained a lot of experience in creating sudoku, I consider that create interesting classic sudoku is the most difficult thing to do. Create a set of 5-6 varied classic sudoku, each with different difficulty and resolution path is not easy. In some tournaments, I think 2 or 3 classic sudoku would have sufficed, the 5-6 presented sudokus not having an uncommon interest and / or all sudokus being too similar, not making the resolution of these sudokus so exciting. Obviously, there are exceptions. Japanese classic sudoku (I think created by the master Tetsuya Nishio) were absolutely beautiful. I also liked the classic sudokus' theme of the serbian tournament.
  My goal here is not to give good or bad points, but since I'm talking about classic sudoku, I can't help but talk about horrible classic sudokus of the first round. Several sudokus required assumptions to be solved, which shocked me. These sudokus have in my opinion nothing to do in a competition, the only effect is to increase the luck factor and to disadvantage players who have the misfortune of trying to find a logical way to solve them. The world upside down for a discipline based on logic! To clarify my point of view: there is nothing wrong and no prohibition to make an assumption to solve a sudoku. Some situations lead players to think they will do a better result if they make an assumption. I always prefer to solve sudokus logically, but it happens to me too from time to time, in competition, to make an assumption when I feel that the puzzle escapes me. On some variants, to make assumptions is not always very useful and can be more difficult to manage because one doesn't always know if he can quickly determine whether the placed digit is right or wrong. The "problem" with the classic sudoku is that it is a chaotic system: if you change / add / remove only one digit of a sudoku, the difficulty can completely change. Thus, a (right) number randomly placed in a very difficult sudoku can make it totally trivial. Luck can change a very difficult sudoku into a very easy problem to solve. My opinion is unequivocal on this point: Even though one knows as an author that a fraction of the players will make an assumption on a very hard classic sudoku, we must always leave the door open to players mastering the techniques and seeking to solve the puzzle logically, even if they know they'll lose a few handfuls of seconds compared to a player who is lucky with an assumption. I was very surprised that the authors of the first tournament and the competition director let such sudokus and I strongly hope not to see such sudokus at the next world championships in London.
• Overall Ranking: The overall ranking, in addition to take into account six tournaments of 7 (5 of 6 in the puzzle competition) against 6 of 8 in the first edition did not include the ranking of players in each tournament, but the performance (number of points) for each tournament, which is a progress. Formula, taking into account only the ratio between the number of points of a player and the number of points of the tournament winner can certainly be improved. Since 6 of the 7 tournaments are taken into account in the overall ranking, it is necessary that the performance of each tournament can be compared. Taking as reference only the performance of the winner is a little weak, but I think this formula will be improved in the future.

Conclusion: I think most of the changes went to the right direction. The small downside, for me, is that every tournament had a bit the same "flavor", there was no real surprise. But it certainly is the price to pay if we want to compare the performances on several tournaments. The number of "puzzlish" sudoku (including star battle sudoku in 2 tournaments, triomino sudoku) was restrained, which is also positive.

Personal result: I think the tournament that I organized was globally appreciated. I didn't hear about disgruntled players or negative points about the sudokus that I created. That was my main goal. After learning that only 6 of the 7 tournaments would be taken into account in the overall standings, my first thought was that I would not be able to reach the top10 meaning a place in the final in London. Also, I completely messed up the first tournament, with a loss of substantial time on 2 classic sudokus that I have not been able to solve in a logical way. Therefore, my goal was to do good performance in each of the remaining tournaments without much worry about the overall ranking. This was the case with a 7th rank in the Serbian round, an 8th rank in the Indian round and the 11th, 12th and 16th place on the other 3 rounds. These are positive results that allow me to reach the 15th rank worldwide, and I firmly believe that a place in the top 10 would have been possible if I could have played all tournaments (I would have needed 71.3 points in a seventh tournament, knowing that my average points on 6 tournaments in which I participated was 75.9).
I also participated in puzzle tournaments without great passion it must be said, and my 81st rank satisfy me.

The finals will take place in London in August, on the sidelines of the World Championships, and will, without a doubt, be exciting to see.

Arrow Sudoku N°14

Règles

• Règles classiques du sudoku,
• Des flèches sont dessinées dans la grille. Au sein d'une flèche, le chiffre situé dans le rond est égal à la somme des chiffres situés sur le reste de la flèche.
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• Classical rules of sudoku,
• Arrows are drawn in the grid. Within an arrow, the digit in the circled cell is equal to the sum of digits on the rest of the arrow.

Grille créée pour la finale du
championnat de Slovaquie (21 juin 2014)

Thermo-sudoku non consécutif N°1

Règles

• Règles classiques du sudoku,
• Deux cases voisines horizontalement et verticalement ne peuvent pas contenir des chiffre consécutifs.
• Des thermomètres sont dessinés dans la grille. Les chiffres présents sur un thermomètre sont strictement croissants en partant du bulbe.
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• Classical rules of sudoku,
• Two vertically or horizontally adjacent cells cannot contain consecutive digits.
• Thermometers are drawn in the grid. Digits on a thermometer are strictly increasing from the bulb.

Grille créée pour le championnat de Slovaquie
(21 juin 2014)

Kropki Sudoku N°5

Règles

• Règles classiques du sudoku,
• Deux cases voisines contenant deux chiffres consécutifs sont toujours séparées d'un rond blanc; deux cases voisines contenant deux chiffres dont l'un vaut le double de l'autre sont toujours séparées d'un rond noir. Deux cases voisines contenant les chiffres 1 et 2 peuvent être séparées d'un rond blanc ou noir.
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• Classical rules of sudoku,
• Two adjacent cells containing two consecutive digits are always separated by a white circle ; two adjacent cells in which one digit is the double of the other one are always separated by a black circle. Two adjacent cells containing the numbers 1 and 2 can be separated by a white or a black circle.

Grille créée pour le championnat de Slovaquie
(21 juin 2014)

Answer 8 sudoku N°3

Règles

• Règles classiques du sudoku,
• Les points dans la grille impliquent que le résultat d'une des opérations binaires (addition, soustraction, multiplication ou division) appliquée sur les deux chiffres voisins vaut 8. S'il n'y a pas de point entre deux cases voisines, 8 ne peut pas être le résultat d'une des opérations binaires sur les deux chiffres contenus dans ces cases.
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• Classical rules of sudoku,
• Dots in the grid imply that applying one of the binary operations (addition, subtraction, multiplication or division) on the two neighboring digits result in the number 8. If there is no dot between adjacent cells, 8 cannot be produced by the two digits going through any binary operations.

Grille créée pour le championnat de Slovaquie
(21 juin 2014)