9. Rules of the Competition (Puzzles)

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9. Rules of the Competition (Puzzles)

Postby WPF » Thu Oct 15, 2015 12:40 pm

Rules of the Competition (Puzzles)
This is a discussion about the section 9. Rules of the Competition (Puzzles) contained in the WPF guidebook that you can download here:
viewtopic.php?f=15&t=162
Prasanna Seshadri
Director - World Puzzle Federation
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Tue Oct 20, 2015 8:30 am

At one point, I would like to open a fundamental discussion about WSC. I feel some discomfort with the fact that there are more and more puzzles that I would hardly put in the sudoku category in sudoku tournaments.
I feel that there are so many things to discuss in this 9th section of the guidebook that I don't really know where to start.
Ok I'll begin with small details.

In page 10: "Points will be awarded only for 100% correctly solved puzzles. There will be no partial credit. A time bonus should be awarded for the solution submitted before the time limit."
I'm fine with that rule. However, some different kind of rules were tried at different WSC: WSC 2010 and 2011 a code for each sudoku could be entered by players if I remember well. WSC 2013 some points were allocated for sudokus with minor mistakes (I don't remember exactly, the criteria was one or 2 cells wrong or empty I think).
My question is: What did we learn about these experiences? Were they bad ideas, so we now return to the rule as written in the guidebook, or were they good and the written sentence in the guidebook should be changed?
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Tue Oct 20, 2015 8:45 am

Now about Play off:

There were lot of discussions on players blog about different systems used as play off. While I think it's not a good idea to fix the play off system in the guidebook, I think this text is not sufficient now to guaranty that some bad ideas in the past doesn't repeat in the next years.
Here are my thoughts:
  • The guidebook should define what is the aim of the play off.
  • The guidebook should define the minimal and maximal number of players that should be qualified for the play off.
  • The guidebook should specify that the best players after the preliminary rounds should have an advantage (time, choice of puzzles, etc...), so that the preliminary rounds which represent something like 90% of the competition is not just a warm up for them. We don't reset the ranking at the beginning of the play off.
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Tue Oct 20, 2015 4:12 pm

I'll speak more specifically about WSC:

One of the best improvement of the last years (WSC and sudoku GP) is that all (or almost all) sudokus appearing in these competitions can be solved by logic.
I think it became a commonly tacite rule (I know that some authors already apply this principle for all the sudokus they create) based on lot of negative feedbacks concerning rounds where players had to guess to solve a lot of sudokus.

Therefore, I think that we now should be ambitious and I suggest to write it in the guidebook:

All sudokus appearing in the WSC should be solvable by the logic.
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Re: 9. Rules of the Competition (Puzzles)

Postby WPF » Sun Oct 25, 2015 8:01 am

Broken Puzzle - proposal by Wei-Hwa Huang
Here's some suggested text for future competition guidelines:

* If a puzzle, intended to have at least one solution, has no valid
solutions due to a small error[1], a competitor can get full credit by
indicating that the puzzle is broken[2], making a small change[3] to
the puzzle so that it does have at least one valid solution, and then
demonstrating a valid solution to the changed puzzle. A competitor
can get partial credit by indicating that the puzzle is broken[2] but
not fixing the puzzle. The amount of partial credit given is up to
the organizer but should generally represent how much time would be
spent on the puzzle before the error becomes evident.

* If a puzzle, intended to have exactly one solution, has multiple
solutions due to a small error[1], a competitor who gets any of the
possible valid solutions should get full credit. A competitor can
also get full credit by indicating that the puzzle is broken[2],
making a small change[3] to the puzzle so that it has exactly one
solution, and demonstrating that solution.

* If a puzzle does not have any errors (that is, it is exactly as the
constructor intended), competitors cannot get credit by changing the
puzzle.

[1] A small error is a small change (see below) introduced to the
puzzle that makes it differ from the intent of the constructor. The
error might have been introduced by printing errors, typesetting,
copying errors, incomplete or incorrect instructions, etc.

[2] One way of indicating that a puzzle is broken would be to write
"BROKEN" on the puzzle. Other indications may also be valid, at the
discretion of the organizer.

[3] An example of a small change would be the addition, removal, or
movement of a number, line, or symbol, either in the puzzle or in the
instructions. The precise details can be dependent on the puzzle type
and should be a judgment call by the grader, possibly escalating to
adjudication as necessary.

Rationale: In an ideal world, puzzles used in a WPC / WSC competition
will be free of errors, and have no unintended solutions. However,
occasionally due to mistakes in checking or printing, such errors can
slip through. Such errors cause problems in competition, because the
competitor might attempt the puzzle in good faith, expecting the
puzzle to be error-free, but then realize that the puzzle is broken,
while other competitors might not have worked on the broken puzzle at
all. The time they invested in solving the broken puzzle could have
been spent to get points elsewhere. The purpose of this rule is so
that a competitor who works on a broken puzzle has a simple recourse
to turn their time investment into points, whereas a competitor who
did not work on a broken puzzle doesn't get an advantage (as they
would if, for example, the puzzle were just thrown out of the round,
or if all competitors received points for the broken puzzle).
However, this rule only works if competitors are aware of this method.
Therefore, we encourage all organizers to adopt such a rule in future
competitions.
Prasanna Seshadri
Director - World Puzzle Federation
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Re: 9. Rules of the Competition (Puzzles)

Postby Realshaggy » Sun Oct 25, 2015 4:16 pm

The discussion about "puzzles solvable by logic" is very old. This is just a collection of facts and opinions that have been brought up regarding this topic in the past, as far as I remember them. (It's in no way an expression of my opinion.)

What means "solvable by logic"?

If it means "You should not have to use Trial and error", than one could say, that technically "Trial and error" (sometimes commonly called "guessing") is just a part of the logic technique "Complete exhaustion of search space". In a competition with logic puzzles, the solver usually stops after he found the first solution, because the puzzle is assumed to have a unique solution.

If it means "The puzzles are only allowed to have the following steps", like steps from the categorization at sudokuwiki.org, than you have examples in both directions which seem to be wrong.
First, there are techniques in the "diabolic" category at this site, that are clearly only "advanced T&E", like Bowman Bingo. Noone would use that in a competition over simple "T&E".
And second, there are puzzles with clearly logical steps, that even the solver at this site is not able to find (I remember an example at the old "motris" blog of Thomas some years ago).
If you cut the list to "only easy or medium techniques are allowed" for the whole contest, then you discriminate solvers, who are actually capable of finding more complicated steps.

Even most of the basic techniques are in fact some kind of "T&E", the only difference is, that you do it in mind. Number "3" may not be in cell 1 for this reason, and not in cell 2 and 3 for another reason, so it has to be in cell 4. There is a difference between the solvers, how many steps they can think ahead without writing such things down and therefore what they consider "T&E".

Another problem with hard puzzles with complicated steps in it is, that it's usually faster to do "T&E" than looking for the hard step. For general puzzles, this is an even more serious problem than in sudokus. There are puzzle types, where the top solvers usually don't solve by logic, because it's much faster to guess an almost solution by intuition and then fix all errors. Categories where this is very common are path puzzles and word puzzles.

And last, there are opinions, that it is not bad to have some puzzles which require some "T&E". Realizing, that you are on a point, where you could save a lot of time by trying something, is a skill worth testing. And even doing the T&E is a skill on its own. In sudoku, you usually have to choose a cell and a candidate, and you have to estimate, how much "easy information" you get with that choice, so that you get either a fast contradiction or enough information to make the puzzle considerably easier.
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Sun Oct 25, 2015 6:36 pm

I would like to open a discussion about puzzles that compose the WSC.

I'm a sudoku player, WSC is about sudoku, so I expect puzzles appearing in WSC (and sudoku GP) to be sudoku. This sentence, which looks like a poor triteness, reveal in contrary an issue : we don't have now a clear definition of sudoku, which would contain classic sudoku and all its variants.
The limits are not clearly defined, thus each player, author, organizer can have different opinions on this subject.

This year, I had troubles with 2 kinds of puzzles encountered in sudoku competitions that I would not have classified as being purely sudoku.

  • Hybrids with other puzzles : there are some variations of sudoku whose idea come from another puzzle type. That's absolutely fine, no problem with that. Such well known variations are for example kropki sudoku and skyscrapers sudoku. Another new idea was born this year : pyramidal sudoku (sudoku GP 2015, round 6) which seems to be an hybrid between sudoku and the puzzle named pyramid : At the end, the puzzle is a sudoku and the external idea acts like constraint between digits in grey cells. Absolutely fine !
    Where I have troubles is when I have the feeling that the external puzzle doesn't merge with the sudoku, it's like the 2 puzzles are superimposed and we have to solve 2 puzzles in once. Examples are battleship sudoku (sudoku GP 2015 round 2, discussion here: http://gp.worldpuzzle.org/content/sudoku-gp-2d-round) and sukaku (sudoku GP 2015 round 4). In those example, the influence of the non-sudoku puzzle is not only to add constraint to place digit. In the first one we also have to place ships in the grid and in the second example we have to divide the grid into rectangles. These are surely nice ideas and nice puzzles, but in my opinion it crosses the boundaries of sudoku, hence they should be part of puzzle competitions, not sudoku competitions.
  • Puzzles that stretch the basic rules of sudoku : This year's WSC contained a few puzzles that I would not have placed in the set of sudoku. I talked about it on my blog: http://sudokuvariante.blogspot.ch/2015/ ... sofia.html.
    There are several ways to stretch or weaken common sudoku rules : use repeated symbols or digits instead of the classic set 123456789. Divide the grid into regions which don't contain N cells (well-known examples : deficit/surplus sudoku, blackout sudoku). Make that finding the limits of regions is a part of the puzzle (well-known example : tripod sudoku), etc... In past years, I think lot of organizers/authors cared about the fact that putting such puzzles into sudoku tournaments meant playing with boundaries of the definition of sudoku. I don't think it's a coincidence if deficit/surplus sudoku appeared in small size in WSC 2010 (5*5!!) and WSC 2014 (7*7). Now in lot of recent situations I have the feeling that these kind of puzzles are now viewed as fully accepted puzzles for sudoku tournament and that they justify to have puzzles that are even further from sudoku.

Here I want to make a small break and precise that I like innovations, new variants, new ideas and my point is certainly not to say that sudoku competitions should be composed only with classic sudoku and well-known variants.

I fear now that we take the turn of having more and more such puzzles in sudoku competitions.
I don't see any problem if the amount and the difficulty of these puzzles are controlled. If I see here and there easy puzzles that I would not qualified as sudoku, that's fine for me (I would not dispute about the 20 points overlapping latin squares of 6th round of WSC – even if it's very clearly not a sudoku). But if entire rounds of WSC are composed with puzzles that can be controversial to be sudoku, then I'll have some difficulty to convince myself that the S of WSC still means Sudoku. Or I have to change completely my understanding of WSC.
I see a flaw where it would be very easy now for a WSC organizer to make a WSC that would be very far from testing player's ability to solve sudoku.
My point of view is that a text should be written in the guidebook to ensure that WSC will still be about sudoku, and that organizers have to care about it. But I'm far to be confident about the fact that this idea is commonly accepted, so now I'm not making a suggestion for the guidebook. I want to open the discussion, and I'll be happy if people that disagree with me explain their point of view, so I could understand it better (now I must admit that I don't understand the point about including these puzzles into sudoku competitions, and that causes sometimes a frustrating feeling to me).
At this point I would also be happy to know the opinion of Slovak team who is in charge of organizing the next WSC.

To finish this long post, I would like to say that if the community decides that everything is allowed for the WSC, then I would be happy if the instruction booklet is published before the registration process begins, so that each player can decide if he wants to take part according to what is proposed.

Sincerely yours,
Fred
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Thu Oct 29, 2015 11:24 pm

Realshaggy wrote:What means "solvable by logic"?

If it means "You should not have to use Trial and error", than one could say, that technically "Trial and error" (sometimes commonly called "guessing") is just a part of the logic technique "Complete exhaustion of search space". In a competition with logic puzzles, the solver usually stops after he found the first solution, because the puzzle is assumed to have a unique solution.

If it means "The puzzles are only allowed to have the following steps", like steps from the categorization at sudokuwiki.org, than you have examples in both directions which seem to be wrong.
First, there are techniques in the "diabolic" category at this site, that are clearly only "advanced T&E", like Bowman Bingo. Noone would use that in a competition over simple "T&E".
And second, there are puzzles with clearly logical steps, that even the solver at this site is not able to find (I remember an example at the old "motris" blog of Thomas some years ago).
If you cut the list to "only easy or medium techniques are allowed" for the whole contest, then you discriminate solvers, who are actually capable of finding more complicated steps.

Even most of the basic techniques are in fact some kind of "T&E", the only difference is, that you do it in mind. Number "3" may not be in cell 1 for this reason, and not in cell 2 and 3 for another reason, so it has to be in cell 4. There is a difference between the solvers, how many steps they can think ahead without writing such things down and therefore what they consider "T&E".


I know this is quite impossible to define exactly what means "solvable by logic". But in the real facts it has a concrete meaning. I only made one guess during the 2 days of WSC, and I'm not sure this guess was essential to solve the sudoku. That's enjoyable for me. When a beginner comes to me and asks me to help him to solve a sudoku that he wasn't able to solve during the round, I'll be happy to explain him how to solve it and perhaps learn him some techniques or tricks. We share a same passion. I don't want to tell him "put a 3 in that cell, and then it'll be easy" or "nobody actually knows how to solve this sudoku" or "download this sudoku solver, it will show you how many forcing chain you need to solve it, but nobody can do it that way in less than one hour".
The same applies for online contest. When I'm not able to solve a sudoku and I ask on the forum of the competition, I'm happy to have an explanation and perhaps learn something new. If I've no answer, then what is the point of suggesting this sudoku?

Realshaggy wrote:Another problem with hard puzzles with complicated steps in it is, that it's usually faster to do "T&E" than looking for the hard step. For general puzzles, this is an even more serious problem than in sudokus. There are puzzle types, where the top solvers usually don't solve by logic, because it's much faster to guess an almost solution by intuition and then fix all errors. Categories where this is very common are path puzzles and word puzzles.


I know it's more complicated for puzzles in WPC: there are some puzzles which are more intuitive or visual. That's why I proposed it for WSC only. Also it doesn't mean players are not allowed to guess if they want to. If they think it's faster to guess, or feel comfortable to use "T&E", or if they are stuck while solving a hard one, they can do it on every puzzle, even those which can be solved with logic.

Realshaggy wrote:And last, there are opinions, that it is not bad to have some puzzles which require some "T&E". Realizing, that you are on a point, where you could save a lot of time by trying something, is a skill worth testing. And even doing the T&E is a skill on its own. In sudoku, you usually have to choose a cell and a candidate, and you have to estimate, how much "easy information" you get with that choice, so that you get either a fast contradiction or enough information to make the puzzle considerably easier.


For the WSC, I think about these rounds of "very hard" classic sudoku, which contained 90% of sudoku that nobody solved with a logical path during the competition. I never heard players who told me it was an enjoyable round. I think it's a real improvement to not have any of these rounds in WSC for ~3 years.

Again, I think the point is not to define exactly what means "solvable by logic" but to write this rule in the guidebook as a guideline for future WSC hosts. And so we remember that at some point we had WSC that contain rounds with "too hard sudoku" and that it was a bad idea.
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Re: 9. Rules of the Competition (Puzzles)

Postby Fred76 » Thu Nov 12, 2015 7:04 pm

I feel a bit alone in the discussion about WSC. However I'll keep going and try to make more precise proposals.

I incidentally came across the "Open Letter to the World Puzzle Federation Regarding Sudoku Championships" written by Thomas Snyder in 2009: http://motris.livejournal.com/70037.html

There are still a lot of things in there that can be applied and that we have to think about concerning WSC.
I would like to talk about the 2 first sections: classic sudoku and variations.

About variations, I think I already exposed my opinion. I found that the sentence in Thomas letter: "While I’ve written a book of Battleship Sudoku, that combines the puzzles Battleship and Sudoku, we can agree that this kind of puzzle – which rewards experience outside of sudoku – is not appropriate at a WSC." is emblematic of the actual situation. More precisely: some authors or organizers don't agree now with this assertion and consciously try to "extend sudoku competition and make it more puzzlish". As a consequence, it means that to be a good WSC player, or good at these sudoku competitions, a player has now to be good at other puzzles, too.
That's where I would place my limits as an author of sudoku tournaments. I think it would be fair that a WSC competitor that is not aware of other puzzles than sudoku should have the same chances as, let's say, an experienced WPC competitor.
(I know the argument: "being good at other puzzles can improve one's sudoku skills", and while I agree at some degree with that, it is not my point here).
I feel a bit embarassed to make a concrete proposal for the guidebook, as it seems to me that the only thing I'm asking is that the only puzzle that should appear in WSC is sudoku, and it sounds a bit incongruous to my ears. I'm still curious to know the limits of other organizers/authors/competitors and to learn other arguments in favor of extending the limits than "I don't like sudoku" or "it would be boring".

About classic sudoku, I think the last 2 WSC had put classic sudokus on the sideline. It's not a good welcome sign for newcomers that perhaps don't have yet a complete picture of all the variants techniques. Having 2 easy classics at the end of each round is probably a good idea, but it doesn't test competitor's ability and speed to solve classic sudoku on its own, as it's more about a choice to solve them or not.

I propose something like that for the guidebook:

There should be at least 2 rounds of classic sudoku at WSC, one round composed by easy/medium classic sudoku and another round composed by "fairly" hard classic sudoku. At the end of the competition, the points gained by competitors on each classic sudoku round should be added to give a "classic sudoku ranking". The best competitor in this "classic sudoku ranking" should be rewarded as being the best classic sudoku solver of the year.

Comments: there are a few very good classic sudoku players. Some of them have not the same level when the whole bunch of variants come into play. They will never have a chance to be well ranked at a WSC, despite their incredible talent at being fast at solving classic sudoku. I think they deserve a special ranking (I think something like that was done during WSC 2010).
I think easy/medium classic sudoku round could be similar as the classic sudoku round of WSC 2014 or 2015. The "fairly" hard classic sudoku round should contain hard but reasonable (as described in Thomas letter) classic sudoku. If I remember correctly, WSC 2013 contained a hard classic sudoku round. I don't remember if every sudoku were "reasonable" or if perhaps one of them was too hard (or it's just that I lack classic sudoku techniques, what is probable).

From a personal point of view, I would be much happier to miss the WSC playoffs because I'm weak at solving classic sudoku than because I don't have WPC skills.

I hope I'll not be the only one to make comments here. It gives an "old grouch" picture of me, which I hope I'm not !
Fred
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Re: 9. Rules of the Competition (Puzzles)

Postby Matus » Sun Dec 13, 2015 6:40 pm

Dear Fred!
Sorry for leaving you alone in the discussion. Here are some of my thoughts, but they are not necessarily identical with my colleaguesˈ ones.

I really appreciate the idea of having the Guidebook, it will be very useful for organizers in the future. However, I hope it will be treated as help, not as a restriction tool. Once it starts commanding the organizers the creative spirit disappears.

From my point of view, the WSCs in both London and Sofia were smooth (regarding the puzzles, rounds, play-off system, etc.), but they missed any crucial point or any gradation. Most of the rounds were approximately the same length, they had a uniform layout with one sudoku per page and a few classics at the end. As for the authors, both the championships were a great parade of technically perfect sudoku reminding their blogs collections. Honestly, although the puzzles themselves were of impressive quality, such uniform competitions do not bring me any kind of emotions.

The uniformity might guarantee the quality but after some time, it becomes boring. The WPF Grand Prix rounds and LMI monthly tests are definitely the best sudoku projects so far but I do not mind omitting some of their parts because I am aware of their preset standard. This is the reason why I am strongly against ordering how many classic sudoku rounds should be at WSC or how many contestants are eligible to the play-offs.

I am not sure whether the answer areas worked well or not. I personally have not ever used them and that is why I am not comfortable with the case where my complete solution is worth the same number of points as some other’s incomplete one. On the other hand, the reduced points’ distribution for sudokus with some minor mistakes seems fairer to me, mostly because they are given to each affected competitor without any exception.

Trying to define the border between Sudoku and Not Sudoku types is not a pleasant topic. I respect your opinion on magic squares and puzzlish sudoku variants. However, are these issues essential or just resulting from your frustration? Yes, in Sofia, there were at least two sudokus that definitely omitted one of the basic Sudoku rules but I am not sure whether their caused the main problems of the championship. The 4th round - Straight was very questionable for me because of its unreasonable point distribution, not the surplus/deficit rules. I am quite disappointed that this decision did not generate any public debate at Q&A session. I do not see any sense of these “against all” rules and I would be very glad if the contestants exercised their veto power.

Of course, we will not force you to solve dozens inappropriate puzzles that are trying to look like sudoku. Please be sure that all of us are experienced sudoku solvers and authors and our goal is to prepare the best possible World Sudoku Championship. We are also familiar with some other topics you mention, so please try not to reveal any other surprises that might be prepared for all of you at WSC 2016 :)

Matus
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