LMI August Sudoku Contest

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This is happening the weekend of 7th/8th of August. Main page details here and there's a forum thread for questions etc here.

I'm not quite sure what to make of this, it certainly looks massively different from any other LMI test they've done so far. David Millar of http://www.thegriddle.net is responsible, who I think Gareth at least knows via Sudoku Xtra.

[gareth]

David's puzzles are often on the easier side (which so far as I'm concerned is a good thing when it comes to Sudoku and variants!) - although not always - so it will be interesting to see what the actual competition is like! It certainly looks very jazzy, and I'm flattered he's included my odd-pair sudoku variant.

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Just a reminder that this is happening this weekend!

[drsteve]

Rather enjoyed that. Not a big Sudoku fan, as those of you who know me may remember, but that was fun.

Say no more until the competition closes...

[gareth]

A great selection of puzzles, and particularly nice when printed out in colour too.

I'm definitely not competitive at Sudoku solving, ably demonstrated by the fact that I spent half the total time on the first round, then did the next three rounds in the same amount of time. I didn't get onto the final round (or at least, not for long enough), but at least I didn't get anything wrong.

[gareth]

Oh, and the odd-pair bits were the best part.

[drsteve]

I didn't get onto the final round (or at least, not for long enough), but at least I didn't get anything wrong.

I guess we got the same score then - got bogged down on two individual grids and had no significant time for round 5.

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Just finished it - will save further discussion until the contest closes - but the odd-pair bits definitely worked nicely in conjunction with the even clues

[PuzzleScot]

That was more fun than I was expecting.
I didn't get to do round 5 either. Won't say any more until it's all over...

[drsteve]

Well, I thought that was a reasonable score for me, but not so sure now, looking at the overall results.

Got bogged down on Round 1 grid 4 and especially Round 4 grid 3, which required at least three attempts. Still not sure what went wrong with that one.

Still, for whatever reason, I'm never going to be a competitive Sudoku solver, so it was a good experience. Definitely be doing the Skyscrapers next week, rather than the somewhat extreme Sudoku competition.

[PuzzleScot]

Ended up skipping round 1 grid 4 after wasting too much time on it.
Also failed to finish the last stage 4 puzzle in time, so I reckon on 270 points for me (over 50%, which is good for me on any timed contest!)
It might have been an idea to practice these before launching straight into the contest - but they were lovely puzzles... Well done to the author (David Millar)!

Spent a lot of time filling all my grids in online, to notice afterwards that it appears only one selected region of each puzzle needed numbers filled in (if you clicked 'show cells to fill')! Oh well, PPPPP! (prior planning prevents poor performance)

[drsteve]

You did get 270 Alan. Log in again to the competition page and click on Results. It actually gave you your own result immediately but now has everyones.

Oh, and I filled in the entire grids as well. But I'm a fast typer and didn't waste enough time to enable me to tackle stage 5.

Interesting that it was the same two puzzles that stalled us. Great minds and all that...

[PuzzleScot]

Ah, I see the 'scores' now - Well done Tom - you did the lot with time to spare!

I see that round 1 puzzle 4 only had 66 correct answers submitted. Hardest puzzle after the three of round 5...

The completion time of the winner is incredulous! I would never doubt Hideako or Byron's times though. wow!

[PuzzleScot]

jaku111 = Jakub Ondrousek. I believe he is actually that fast!

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He is indeed that fast - I believe there is a youtube video of him solving a classic sudoku in about 40 seconds or something even more obscene. Looking down the list also is janoslaw - Jan Mrozowski - who had them all done in a similar time but made a typo to drop points and bonus. Neither is as strong generally (puzzling wise that is) as Byron or Hideaki, although I am led to believe that Jan will be one of the team responsible for the WPC puzzles this year...

I actually don't like their online flash thing so I printed out and then used the entry key system, so if you are used to the interface then that can save yourself a minute or two. Even then I spent a little bit of time correcting minor errors I'd made.

Very interesting to see increased Japanese participation as well.

I found that everything flowed quite nicely - the one thing I will say is that on a couple of the rounds there were puzzles that you could whizz through in less than a minute, and a couple were decidedly more tricky to crack. I'm very comfortable with all of those constraints except the greater than and the odd-pair. Like I said, the odd pair turned out to be a very nice extension of odd/even, and the greater than I still need to persevere with!

Will be interesting to see what David does with this. I suspect this sort of speed competition would be right up his street!

[Fred76]

The completion time of the winner is incredulous! I would never doubt Hideako or Byron's times though. wow!

jaku111 = Jakub Ondrousek. I believe he is actually that fast!

Thanks !!!

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Fred - first of all congratulations on your excellent result!

I think all Alan means by these comments is that he has had the pleasure of watching Byron and Hideaki perform incredulous solving feats live at previous WPC's. The main leanings of this forum so far are more general puzzles than sudoku, so not everyone is fully aware of the main players in the sudoku community...yet!

I can fully see that to the uninitiated that blasting through 18 puzzles in an hour or less seems pretty mind-blowing - I know lots were only 6x6 grids (therefore susceptible to brute force if you get stuck) but that's approaching 3 mins a grid!!

[gareth]

Well I got 10 points less than Steve because I simply could not do the fourth puzzle in the first round! In fact I still can't do it now (I mean, I could of course do it fairly quickly by guessing since there are only so many possibilities, but I don't want to do that. ). I also went wrong on the third puzzle in round four initially too - I couldn't get the bottom-middle box to solve with what I had, so I took a chance and guessed I had somehow ended up with the wrong one of the two options for the bottom-left difference box and so started by putting in the other option, and then the whole thing fell out. So I think I was just lucky there mostly!

I always find it amazing how much Sudoku solving speeds vary for people - I generally finish in the top 10% for Sudoku on Nikoli.com but that is still at least two to three times slower than the fastest solvers like Tom! When I analyse my Sudoku solving I can see it usually involves me making the harder deductions pretty quickly but then getting stuck on the relatively easy bits... perhaps if I learnt to step back and scan the whole grid more often I'd be a bit faster. But probably not.

[davmillar]

Thank you all for the kind words regarding the puzzles!

Round 1 grid 4 was very tricky for a lot of people. Part of it involved realizing something about the bottom left 3x2 box, but I won't say more than that and spoil the fun. (...unless I'm asked to do so!)

In a way I'm slightly disappointed that many solvers were not able to get to round 5 in time, but on the other hand I'm pleased to hear many want to try them anyway at a more leisurely pace. If any of you are interested, there are 4 additional puzzles in the style of rounds 4 and 5 at http://thegriddle.net/521. The ones in the style of round 5 are also slightly interesting because they have absolutely nothing in the center 3x3 box.

I'm always looking to feedback on puzzle creation (and on design!) and would love any additional comments from anyone and everyone.

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I've had a check back to round 1 puzzle 4. I've just realised I've used a similar trick in some of my own consecutive sudoku puzzles, which is probably why I got through that puzzle without blinking!

David - I think that pitching a sudoku competition at the right level is very tricky, you'll certainly never please all the people all of the time. The last LMI test - by Jan Mrozowski - featured some really good puzzles, but the difficulty was turned up to about 8 or 9 and was probably unsuitable for beginners. Your test wasn't as hard, and most (not all!) seasoned sudoku pros managed to blitz through it fairly quickly. On the other hand, it did offer something for everyone, and whilst not everyone is going to be able to do everything in time, the beauty of these contests is that you can back later and solve (and more often than not, self kick!)

I think you can measure your success by the comments from our resident sudoku sceptics!

[gareth]

Ah! I suppose the deduction is that the left-over numbers from the chain can't be consecutive, and then of course you know what the chain is (although not the order) and what is left for those two boxes?

I completely, utterly forgot that consecutive parts of the puzzle have a non-consecutive rule too. No excuse for that, mind! Although, that said, I think it's the effect of having all the different rule types - your brain naturally focuses on the positive meanings of each clue, not the negative ones (I also didn't once apply the 'not odd pair' anti rule either when solving). Well my brain does anyway!

The statistics seem to show that this brain blockage affects almost precisely 50% of Sudoku solvers.

I couldn't see this any of the three times I looked today either. I think this was a rather tricky 10 point deduction! But brilliant.

[Fred76]

I know lots were only 6x6 grids (therefore susceptible to brute force if you get stuck)

I'm not brutal !!

[drsteve]

I think you can measure your success by the comments from our resident sudoku sceptics!

Speaking a sceptic, this was one of the most entertaining competitions that I've done. Obviously the uber-solvers rattled through it, but for a general puzzler, rather than a sudoku specialist, I found this a very enjoyable challenge. Compare it to the upcoming Quixy challenge that seems a little pointless for a non-expert. Many thanks!