Sunday 30 October 2022

Unofficial Championship Host's Guidebook

Before I get going, a couple of quick note to self: 

  1. Move this somewhere more permanent on the blog, and dig up other similar posts!
  2. Finish the post!

I don't know exactly how much appetite there is for this kind of post, but I don't think it's of no interest at all.  Hopefully it's of more interest than the existing WPF guidebook that exists somewhere on the internet, but that I am not interested enough in to find and link to right now.

The best approach to this kind of thing is to somehow work backwards from a successful outcome.  To that end, I will draw on my many experiences as a competition participant as well as my experience as a competition organiser to run through all the things a participant tends to experience at a well-run event.

These then can be regrouped from an organiser's point of view.

Tuesday 25 October 2022

WSPC 22: Aftermath

So the intention wasn’t to leave the last post as something of a cliffhanger, but it turns out I didn’t really have the energy to do updates during the week. 

The first thing to say is that the week was a bit of a rollercoaster. There were some unpleasant lows I won’t speak more about, but they left me feeling greatly saddened and robbed me of both self-esteem and proper sleep during the week. That’s never ideal when you want to be at peak mental sharpness, to say the least.

But overall it was great to return to things after 3 long years away. The puzzle solving itself also had its ups and downs; that’s usually the case but this year I was well within my usual abilities. I do think the WPC in particular will go down as a classic vintage. The 3 years away has given the opportunity for a new generation of solvers and authors to break through, and it has been a real delight to meet some of them and start new friendships. And of course to meet dear old friends once again.

I’ll be doing some posts with the added benefit of hindsight when I’m back to London. These will probably focus more on the highs as I think it’s about time to put the aforementioned lows behind now. 

Tuesday 18 October 2022

WSPC 22: Ouch

I didn’t get around to finish posting yesterday, having been totally drained of all energy: mental, physical, emotional. It seems cruel that insomnia now prevents me from finding rest and peace for the night. 

I don’t know if I’ll keep posting through the rest of the week. To be honest, yesterday hit me pretty hard, as I’m sure anyone reading this is beginning to realise. I really wanted to make a good year of it, and I thought I was supposed to be reasonably good at this stuff, but everything seems to be falling apart and I can’t seem to process any of it. I’m in a pretty low place, feeling helpless and useless and in need of a hug. 

Monday 17 October 2022

WSPC 22: Day 1

On to the first day of competition at the world sudoku championships. I started the day full of excitement, but perhaps not quite with a level of mental sharpness ready to start the competition. 

We’re up to lunch now and I’m licking my wounds; the morning’s solving counts as one of the more chastening experiences I have had in 15+ years of solving. 

I’ll edit in more later, but for now I am at least comforted by the general consensus in the room that it has been hard! Seriously hard! Hard enough to make me wonder whether having a non-zero round represents a good achievement now. I will be even more studiously avoiding anything looking like scores or a leaderboard from now on. That was always going to be the case, but the readjusting of expectations this morning has hit me hard and left me low and disappointed. 

The first round was classics only, and I think the only way to look at things is an acceptance I choked. I got one puzzle done, tried enough twice, convinced myself there was an unresolvable contradiction and from there on in I was making errors left right and centre. 

The rounds after were disappointing in many ways. The second was looking ok, but ended up spending a lot of time on a puzzle without being able to finish it. Round 3 had a combination of 1 and 2’s woes, wasting a large amount of time on a puzzle I was convinced could not have a solution. Round 4 was just hard all round - no contradictions this time, but also not much in the way of puzzles solved either. I think I might have one. 

The morning ended with round 5, a very large samurai sudoku with 14 overlapping grids. Speaking with others this was also very hard, but I finally managed to get a good round under my belt. I’ll claim 11/14 completed grids in the 30 minutes - which is going to be close to my round 1-4 scores combined if there are no errors. Let’s hope not!

As far as the contenders are going, I don’t really have a feel for things. I had a nice chat with the ever-kind Tiit Vunk about the mental side of long distance running - he’s not feeling the pressure too much this year and is instead focussing on enjoying all the puzzles he’s able to solve. I’m not sure many are finishing rounds, or even close to, but performance of the day goes to Kota Morinishi - he got that Samurai out in what I think was 18 minutes. 14 9x9 grids in 18 minutes! And that’s with what felt like the requirement to place numbers in about 8 of them before you could really get going. I think I heard Tantan declare with roughly 5 to go as well, but I think given how things have gone so far I can imagine Kota being an imperious position at the front of the pack. 

On to the afternoon!

Sunday 16 October 2022

WSPC 22: Day 0

So I was hoping to post a bit more earlier today but now I’ll keep it brief. The official arrivals day started pleasantly with breakfast with old friends from Poland on the organising team. It’s like 3 years of madness that have past since we all last met in 2019 washed away - and pretty much references to “last year” throughout the day as people arrived became an agreed standard. 

It was nice to share stories from fellow championship organisers - our efforts date back a few years now to 2014 - but also a little sobering to hear about the impact of the Russian invasion of Ukraine on Poland, particularly with regards to military logistics. Later meeting some of the Japanese team brought tales of longer flight times due to diversions around Russian airspace. This year, there is no Russian presence at the championships as there usually would be, although a good friend from Belarus did manage to make it. These issues of course are far bigger than a puzzle championship, but that doesn’t mean they should not be discussed or shied away from. 

After a walk through some nearby woods in the crisp autumn sunshine, the rest of the day was spent in the hotel greeting a steady stream of arrivals. The UK team is all here now and looking forward to the competition. I’m curious to see how newcomer Jack does at his first competition, and I was pleased to tease Cracking The Cryptic’s Mark Goodliffe that he was probably the most famous person here, with his 500,000+ follows. Probably enough to outdo the likes of Will Shortz, even if he has had cameos on the Simpsons and his I met your mother. 

Perhaps my favourite time of the day was spent well with my good friend of many years now and anlso general all-round Chinese phenomenon Tantan Dai. I’m probably not totally partial here, but I think she is a narrow favourite for the Sudoku title ahead of the likes of Estonia’s Tiit Vunk and serial world champion from Japan Kota Morinishi. Those three are all mind-blowingly talented as well as being really good decent people in a way that it is hard to do justice - whoever comes out on top will be a worthy winner - but this year I’ll be firmly rooting for Tantan!

No surprises in the evenings Q&A - although the team rounds sound like they might be eventful. More to come tomorrow!

WSPC 22: Day -1

So here’s to the revival of detuned radio’s championship reports!  I don't have a laptop with me this year however I’ll see what I can do tapping things out on a phone. I don’t think I’ll be in depth with all the gory details as I once was, and I think I’ll try to be at least somewhat journalistic about proceedings, aiming at an audience who sort of knows what puzzles are but don’t really know what the world championships are all about. 

I am here, finally, in Krakow. About 4 hours late, and sorely missing the company of others I’d hoped to catch this evening who have very sensibly gone to bed. I have sworn many times never to fly Wizz Air again, but I think this time is probably the last. I look forward to an epic fight to claim my rightful €250 when I get back home. 

To set the scene about the championships, I can share some of my day idly spent staring at a phone within the confines of Gatwick airport. 

At both the WSC: and the WPC: there is about as much variety in sudoku and logic puzzle grids that you could hope to throw a forest worth of sticks at. (Maybe that should be pencils?).  I encourage my dearest readers to follow those links, scroll down to view the instruction booklets, and prepare yourselves.

I have been doing these things since 2007, so I reckon I qualify as a seasoned pro at these things by now; but I doubt you will be that much more bewildered by it all than I am. I suppose I’ve done just enough reading to at least understand all the rules now, but there will be more than a few types that I will encounter for the first time when it really matters, in the competition itself. 

I might save more on the puzzles themselves for tomorrow. It’s getting late and there’s a long week ahead. I’m glad to be back at championships for the first time since 2019, to seeing old friends once again, and also to see how well the competitive juices get going again. My thanks also to the organisers for all they have already done in preparation - I was there in 2014 and once you’ve been through that, you certainly have my solidarity!

Monday 30 May 2022

pzprPT Masyu experiment

I thought I'd try the same thing as the previous post using the pzprRT interface - this time with Masyu.  

UPDATE: I managed to put out 15 puzzles, which seems absolutely insane to me.  I had speculated that the interface might be a bit more fiddly with Masyu, because you can't just type in numbers - however what won through is the fact that you need far fewer clues to get a valid Masyu puzzle.  So there we go, churn out a puzzle in an average of 2 minutes.  Make of that what you will!

Solved in 0'50.  A fairly tricky puzzle in the end, although enabled with a repetition of my favourite diagonal pairs in the corner.

Solved in 0'44.  Mostly smooth, although a couple of tricky deductions.  My initial impressions are this has been a bit more successful than the Slitherlink experiment to come up with puzzles that don't feel too artificial.

Solved in 1'41.  This is the first one I feel like I missed something - maybe too early to say if that points at a computer generated hallmark, although I didn't really like this as much.

Solved in 0'33.  The theme suffered in order to get something unique out, but this was a lovely smooth puzzle to solve.  I might try and rescue this at a later date!

Solved in 1'09.  Solved nicely enough, but with a couple of moments to sit and think.  But these aren't feeling so artificial to me.  I wonder if that's because I'm a reasonably proficient Masyu solver and just get these things quicker than I do with Slitherlink?  Or indeed if there's an upper limit as to how hard you can make Masyu?

Solved in 0'26.  Finally got an anti-symmetric one going, and it's just as good as any other in this style that I've ever written.  Interesting!

Solved in 0'27.  On a roll with anti-symmetry.  This one has a really nice design actually - maybe it compares favourably to most of the others in this style I've ever written.  Hmmm!

Solved in 0'49.  I'm beginning to enjoy these!  This one had a couple of my favourite patterns to get things going.

Solved in 0'36.  Fine again!  A perfectly reasonable puzzle with a don't close the loop early theme.

Solved in 0'35.  Felt like a perfectly good themed puzzle that solved very smoothly to me.

Solved in 1'24.  Admittedly I guessed here - I wasn't expecting a puzzle with a random selection of white pearls to give anything other than something that needed guesswork.

Solved in 0'30.  I guess all-black pearl puzzles are always going to be less interesting.

Solved in 0'52.  This attempt at anti-symmetry didn't quite work out, but a perfectly decent puzzle!

Solved in 0'37.  Another nice solve!

Solved in 0'36 - more antisymmetry and solved well enough.

Sunday 29 May 2022

pzprRT slitherlink experiment

Perhaps I'll reflect more on this after I finish the experiment - but for the time being I'm going to live-blog a slitherlink puzzle setting process which relies entirely on the hugely impressive pzprRT project.  Let's see how many puzzles I can publish in the next 30 minutes...

UPDATE: The answer is 9 puzzles, which feels like a lot for 30 minutes worth of work.  I have now gone through and solved them all - they are unique and cover a surprising range of difficulty levels.  Some of them are more fun to solve than others!

Here are the puzzles:

Solved in 1'02.  The solve was a bit disjointed solving symmetric parts of the grid, but after that it was surprisingly smooth.  Not the ugliest looking puzzle in the world either.

Solved in 1'59.  A smooth enough start to the puzzle, it got a bit fiddly at the end.  Some interesting topological deductions in play here but it did feel somehow artificial.

Solved in 4'29.  I didn't want to have to guess to solve any of these puzzles, but I ended up doing so here.  There's probably a clever topological argument at play here, but this one definitely feels the most computer generated puzzle so far.

Solved in 3'13.  Again needed to guess to finish things off at the end, so pretty hard.  You can kind of see how I tried to build up a theme, and then compromised it quickly in order to get out the unique solution.  Not amazing either.

Solved in 1'54.  This one I remember trying to set by including a few patterns of clues I'm familiar with.  It kind of works, but not entirely successfully.  Definitely better than the previous two, but still with an undeniable artificial feeling to it.

Solved in 1'36.  This one is largely easy and with a smooth solve, except for a fiddly end which kind of ruins things a bit.  Again you can see how the initial visual theme got watered down a bit.  I suspect it wouldn't take that much work on this to keep the theme stronger and have a more consistent solve.

Solved in 1'20.  Basically a taburega puzzle for those familiar with the reference.  Solves smoothly and with a couple of interesting moments, but always with the sense that the thing is one big gimmick.

Solved in 2'16.  This one felt very computer generated.

Solved in 0'29.  Nice to have an easy one, although that was always going to be the case using patterns like this.  I suppose if I'm honest I'd have to say this one is fairly taburega-like as well.

Wednesday 16 February 2022

Results: Sudoku Design Competition

Here's what you've all been waiting for dearest reader, the big reveal!

Firstly, in a completely randomly generated order, here are your (mostly) esteemed and highly talented authors.  I will be in touch over the next few days about the best way to send over the prizes.

Entry A - 0403 came courtesy of Yunus Emre Büyükkale
Entry B - 3233 came courtesy of Tom Collyer (yes, that use of the word "mostly" is there for a reason)
Entry C - 4235 came courtesy of Anuraag Sahay
Entry D - 4438 came courtesy of Jiri Hrdina
Entry E - 5308 came courtesy of Sinchai Rungsangrattanakul
Entry F - 5617 came courtesy of Yoshi Baroshi
Entry G - 6071 came courtesy of Kumaresan R
Entry H - 6283 came courtesy of Gareth Moore
Entry I - 7408 came courtesy of Florian Wortmann
Entry J - 7704 came courtesy of tamz29
Entry K - 9133 came courtesy of Sam Cappleman-Lynes
Entry L - 9158 came courtesy of Jack Lance

[I will edit in a link to a permanent page on this blog to showcase the entries in all their glory, as well as update the PDF.  For now the puzzles can be found:]
I have to say that I went to great lengths to draw up entries as soon I received them to anonymise them and leave until after the closing date, so that I had the best chance of not knowing whose puzzle I was solving as I was going through.  The original idea with 3 picks for me was to roughly group into an easy, medium and hard puzzle, but it didn't quite work out that way in the end.  The first three £25 prizes go to:
  • Entry D - Jiri Hrdina
I thought this was a wonderfully smooth-solving easy puzzle, setting up the obvious hidden pairs in boxes 2, 4, 6 and 8.  These boxes together with box 5 then resolve themselves leaving the corners of the puzzle to be mopped up via some more hidden single.  The sort of highly polished easy puzzle I really appreciate!
  • Entry H - Gareth Moore
I thought this puzzle moved away from an easy level in a very pleasing way, nicely setting up a naked triple half-way through the solve; this was definitely something that set this puzzle apart for me.  

But don't just take my word for it, one very experienced sudoku solver thought that:
H - clearly a favourite. It has a nice solving path, not too easy / not ridiculously hard. ... It would be a good puzzle for the WSC finals or something.
  • Entry L - Jack Lance
Last but certainly not least, as soon as I saw entry L I knew I had a winner on my hands.  The symmetry of this puzzle is absolutely stunning with consecutive pairs arranged in Battenberg formation around the grid, attached to another consecutive pair for good measure.  However what I find most pleasing about the symmetry is that it doesn't fall into the pastiched trap of a Gurth's Theorem situation where you only get to solve half (or even a quarter) of a puzzle.  Crucially with this puzzle different given digits in the grid are not rotational symmetric from other given digits, which breaks the symmetry and ensures the puzzle maintains an interesting, albeit easier solve.  Absolutely beautiful - this is the single puzzle from the set that I wish I had written and in my eyes is now *the* definitive puzzle for this layout.  For whatever that is worth :-)

Finally, the last £25 went down to the public vote.  My previous post announced that I would be disregarding votes from the authors themselves, but in the end this made no difference to the overall winner.  Which is:
  • Entry G - Kumaresan R
Interestingly my dearest readers plumped for one of the Extra Hard puzzles, which i think neatly wraps up the set of prizes (I should add I had picked my favourites before I counted the votes - in theory an entry could have one two prizes).  It must be said Extra Hard in this case comes with a bit of a health warning - you can use a uniqueness technique to turn this puzzle into a much smoother solve, however knowing that some solvers prefer not to use uniqueness if they can help it, this was how I felt I had to rate the puzzle.

The author had this to say about the puzzle: 
Actually it is not hard but an advance technique is involved. Without this technique unique rectangle can be used to complete the puzzle.
Whilst another solver said:
The puzzle I preferred requires a very unusual way of uniqueness, which once found solves the puzzle. Not sure for the 10/10 rating for difficulty since it was an easy spot, but surely 10/10 of cleverness!
Narrowly losing out in the public vote (regardless of whether author votes were taken into account or not) were entries H and F.  We've already discussed entry H, but entry F was the other Extra Hard entry from the set, and perhaps demonstrates that there is something of an appetite for more difficult puzzles.

That's it for now - congratulations to all the participants and especially the 4 winners!  I'll probably look to do some more of these fixed layout competitions with other puzzle style in the future, as I think it went down well with both those who submitted a puzzle as well as those who voted on them.  

Tuesday 15 February 2022

Puzzle design competition: results soon

This will be the penultimate post regarding the puzzle design competition. I have decided my top 3 and will be republishing the puzzles with credit over the next couple of days.  I hope you are all looking forward to finally being able to put names to puzzles!

I had fewer votes (10) than entries (12), which I find very curious - I’d like to hear what factors might have been holding people back, even if it’s just speculation.  To those who did vote, thank you very much for participating and leaving your comments, I am glad that you enjoyed this idea.

Some of the 10 votes were from entrants, which I had assumed wouldn’t really matter given I was expecting far more votes than entries, however before tallying up the votes it seems like the only sensible thing to do is to disregard author votes. I can’t see how an individual vote for oneself would not be significant in these circumstances, and given not every author voted there is clear unfairness here in my eyes. 

Saturday 12 February 2022

Public vote closes soon

A friendly reminder to all my dearest readers that the public vote for your favourite entries from the puzzle design competition is closing soon - 23:59 GMT on Monday 14th February. 

I don’t have all that many votes right now so it’s be good to change this over the next couple of days to see if we can settle on a clear winner. 

I hope everyone has been enjoying the puzzles so far!

Friday 4 February 2022

Puzzle Design Competition - Public Vote

Hi everyone,

In case you haven't already seen, I have published the anonymised entries of the Sudoku Fixed Layout Design Competition.  Thanks once again to each of the authors who contributed a puzzle.

The puzzles can be found:
Please note that I haven't asked the authors whether they are happy to provide links to online solving tools, so please take this into consideration before transposing the puzzles and sharing.

As a reminder, I will be awarding 3 x £25 prizes to my person favourites.  The fourth £25 prize will be awarded to the winner of the public vote.

In order to vote, you need to select your own 3 favourite entries and order them in preference.  Your first preference will score 5 points, your second will score 3 points, and your 3rd will score 1 point.  At the end I'll add up the points and whoever has the most will win.

To ensure that people only vote once, the form requires you to be logged in to google.  If this is a concern to you, please leave a comment and I'll see if there's another way that you're able to cast a vote.

Closing date for votes will be: 23.59pm GMT on Monday 14th February.

Tuesday 1 February 2022

Puzzle Design Competition - Anonymised Entries

I am pleased to announce there were a total of 12 entries to the Sudoku Fixed Layout Design Competition.  Thank you very much to everyone who submitted an entry, I am honoured that each of you took the time to participate and I am super excited to get solving and judging what I am sure are going to be a truly extraordinary set of puzzles!

I am in a bit of a rush at the time of the initial post - expect this post to updated, probably with a PDF attachment for your printing convenience.  Please note that I haven't asked the authors whether they are happy to provide links to online solving tools, so please take this into consideration before transposing the puzzles and sharing.

UPDATE: difficulty ratings have been added to the post below, and I have also put together a PDF file.  Please note the difficulty ratings are based on my initial solves - a sample of 1 is not usually great for the purposes of testing so do take these with a pinch of a salt.  It is fair to say that the two entries rated at 10 / 10 are significantly more difficult than the rest of the set however!

PDF of entries

Expect a further post in the next couple of days with the voting form and corresponding deadline (which will be in at least a week's time), but in the meantime I thought all my dearest readers would be very keen to get solving as well.

Entries have been anonymised using four random digits as a reference.  I will further update this page with a rough indication of difficult a bit later; for now I will add that, based on the authors' self-assessments, the difficult levels within the collection range from easy through to very difficult.

The last thing to say is that I have run these puzzles through a computer checker to verify they solve uniquely only *after* I have redrawn into a standard format, so this should mean that there are no transposition errors below.  If not, please let me know in the comments.

Saturday 22 January 2022

Update - Puzzle Design Competition

This is a quick update on the previous post.  I haven't really given much thought to how the public vote is going to work, so I've decided to keep it simple.

All the entries will be anonymised and published after the closing date of 31st January, and I will set up a new google form for you to pick your own top 3.  First preference will be awarded 5 points, second preference 3 points and third preference 1 point.  I'll then tot everything up and the entry with the most points will be the public winner.

I'll tentatively say that I'll keep the vote open for about a week after I publish the anonymised submissions.  it really depends on the number of submissions as I'd like to give everyone a reasonable amount of time to solve the puzzles and come to an informed decision about their favourites.

After the public vote I'll publish all the entries with full credit, and contact the winners for the best way to send across the prize money.

That's all for now, I'm really looking forward to solving all these great entries.  Thanks to everyone who has submitted so far.

Wednesday 5 January 2022

New Year Puzzle Design Competition

Somewhat on a whim, dearest reader, I have decided to try and revive one of the lesser known institutions of  The idea was to gather together as many authors as possible to see what they could collectively achieve when they are additionally constrained by a fixed layout of givens.

I'd like to think this would work as an idea all by itself, but by means of encouragement I am willing to offer cash prizes of £25 to my three favourites.  An additional prize of £25 is offered to the winner of a public vote.  I will be accepting entries until the 31st January.

The Puzzle and the Layout:
For this competition, I have chosen Sudoku, without any extra rules, constraints or other variations.  The layout of givens I would like you to follow is this one:

This layout is close to my heart, being very similar to the first ever puzzle I published on this blog back in 2009.  Back then I couldn't quite get this working without having to add an extra given digit at R5C5, but I'm sure my dearest readers will be able to manage without that.  

As an example, I made a small nod to this in one puzzle I made for the 2014 World Sudoku Championships.  This puzzle was additionally designed so that there was no given 9 in the grid.

Submitting your Entry:
This should work via the following google form:

Please let me know if this isn't working for you.  I think it requires you to be signed in to Google to work, and you will need to attach your entry in a PDF or Image format.

The form should additionally allow you to edit your entry after submitting if you think you can do better, although please note that it will only accept one submission.

  • No more than one entry per person.
  • Collaborations between two or more people are permitted (However you will have to determine how to share any prizes).
  • Each entry must be:
    • A uniquely solvable puzzle under sudoku rules (no extra constraints or grid decorations permitted).
    • Have given digits as per the given layout.
    • Not totally computer generated (some computer assistance is fine).
  • The last date I will accept entries is 23:59 GMT on Monday 31st January 2022.
  • By submitting an entry, you retain full author's copyright, but agree to let me redraw your entry and publish it (with credit to you) on my blog.
  • Entries must not be shared or discussed with other entrants before the winners have been declared.
I reserve the right to disqualify entrants and entries not conforming to these rules.  My decisions are final.

  • This will kind of depend on how well I've chosen the layout, and the entries received.
  • The overall prize pool is £100.  This will include £25 each for my three favourite entries, and a further £25 for the public vote.
  • I am happy to send prizes internationally using services such as Wise - although please note that prizes will also need to cover any associated charges and fees.
  • You do not have to claim the prize if you do not want to.

After the closing date I will anonymously draw up the entries for your solving pleasure.  I am not sure how many entries I will get so I won't commit to a publishing date.  However, after the entries have been published there will be a 7 day voting period.  I will have a think about exactly how I want the voting system to work, but it is likely to involve individuals picking their top 3, and me somehow aggregating this information all together!

Any attempts to manipulate the voting will result in disqualification for the public vote prize.

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