This grid is perhaps a bit hard for the instructions booklet. Prasanna is right, you must study the 9's and try to find a contradiction. I think it's the only possibility to crack this grid.
For example, if you try to put a 9 in R6C1, then you have a 9 in R9C3 (only option is that box), then it has to be in R8C9 (only option in this row), then in R4C7 and then you cannot place a 9 in column 8.

So you know that R6C1 is not a 9, and then it becomes easier to finish the grid.





Attachments
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queen_swaroop.png (19KB - 4 downloads)

I've just published a grid which will help you to immerse in a diagonal world smoothly, with just a classic sudoku :

http://sudokuvariante.blogspot.com/2012/03/sudoku-classique-n1.html

Fred

Hey to Prassana and Fred,
for helping it out..
Will try now and see.
It is the tough one in comparison to all other grids.
:)

grt grids....thanks Fred and Team LMI!!!

Thanks Fred for creating this great test and thanks to LMI team for hosting it flawlessly.

This is easily the longest I've stayed in the top 10 of an LMI test. That might be more to do with them being extended to Monday though

No doubt: you become a sudoku specialist !

Funnily enough my most significant steps in improving in Sudoku tests have come after I've started concentrating on puzzles. I'll just keep doing what I've been doing.

Nice to see you improving both in puzzles and Sudoku.

Not the right test to solve from back to front.... Oh well. Some impressively difficult puzzles here, thanks.

Thanks for participating.
I'll comment about the difficulty when the test will be finished. I hope you had fun nevertheless.

Fred

Thanks !
And thanks to all players for having sweated on my grids !

More comments tomorrow, I need to sleep now

Fred

Diagonal Vision is now over. Link to score page - http://logicmastersindia.com/M201203S/score.asp

Congratulations to flooser, janoslaw and TiiT for taking the top spots.

196 players participated and 154 of them submitted at least one grid correctly. The grids were tough, but it is bit surprising to see no submissions from many regular players (Rohan / Rakesh / Stefano )

Thank you everyone for participating.
And Thanks Fred for all your efforts. Will wait to hear more from you.

I did enjoy several of the individual puzzles, which showcased some pretty creative execution of some of these variations. The Pointing Evens was probably my favorite, with a 1,2,3,4 theme where each of the numbers actually mattered, not just the small ones. Many other themes were nice too even if the puzzles were less friendly.

I guess my competition complaint is that I particularly would not advertise "top players will be able to solve all sudokus earlier than 120 minutes" unless this really was a 90 minute test for people like Jan and Tiit and Kota or the winner Florian. My expectations were for some easier grids and even the first Argyle is hardly a 4-5 minute puzzle at least for me. It's possible that I'm not as good at sudoku as I think I am, or it's possible these puzzles are insanely hard. Probably some amount of both is true. But I was left with the same feeling as after Crazy Arrows of "wow, that test is insane." I loved the puzzles, but I don't know if they all belong in a competition. Maybe my views of 10 minutes is as hard as a competition sudoku should be and X- or Y-wings are as hard as a competition sudoku should get are wrong. This test certainly pushed them to the limit.

Edited by motris 2012-03-13 7:46 AM

I'll let Fred put more comments later (and Fred, correct me if I'm wrong), but from our earlier discussion, I figure that the intention was that top players should be able to solve around 100 minutes. At least the test solver's timings suggested so.

Prasanna was the first player to take the test, and looking at his score, we really thought that it is possible for top players should be able to solve better than what the final results suggest. Little did we realize that Prasanna has improved a lot in recent times.

I realize that a statement like "It is expected that top players will be able to solve all sudokus earlier than 120 minutes." look certainly misleading now. [ I had put it originally in Sudoku A/B, where I thought I should let players know that it is more like a Sprint test and not otherwise. ] May be because of that line you started solving from the end, expecting that you are anyway going to solve all sudokus. Obviously, Fred's intention was never to mislead any player.

In my case, it is not because of the toughness of the grids. I somehow did not manage to find a two hour window for the test. And since there were only a few hours left yesterday, even though I was sleepy, I started the (online) test hoping I would be able to stay awake the next couple of hours. But I did not manage it and decided to stop after hardly ten minutes - one grid (anti diagonal) was close to completion but I did not submit as I was anyway going to stop.

Congratulations to all winners and Prasanna for an impressive finish !!

Edited by rakesh_rai 2012-03-13 11:30 AM

Thanks Rakesh.

Coming to the difficulty, I tested all the grids after I completed the test. To be honest, I too expected a lot of people to finish this one, for 3 reasons.
1. I don't really think diagonals are my strength, and I'm never comfortable solving them.
2. I was about a few seconds away from submitting the Diagonal Consecutive, which means there were just 3 grids I didn't solve in the allocated time.
3. Later on, I solved the arrows one quickly enough considering its points, I took long on Argyle and Creasing but I always knew I was gonna get extremely confused on those and thats why avoided them during the test, but since they were low pointers I assumed they were easily solvable for the top players too.

Anyway, all 3 of us Deb, me and Fred expected many to finish this. I'm glad on the personal side as I've moved up, but from a tester's point of view, I apologize that I didn't really give a good evaluation of the grids, but that was not at all intentional.

Edited by prasanna16391 2012-03-13 2:18 PM

All compliments to the author. This was the best sudoku test here, premium puzzles, all of them with very nice solving path. I especially liked new outside and skyscrapers variation. Bravo Fred!

I agree with Thomas, the sentence "top players will be able to solve all sudokus earlier than 120 minutes" should not be here, nor in any other test. This should be the default. Anyway, I don't pay too much attention to it, but someone else could be frustrated. Congrats to Florian!

Nikola

Thanks, Nikola !
I'm happy that you liked the grids !

Congratulations to Florian, Jan and Tiit for taking the 3 first places of this hard test !

Florian also win a beer, as the best German player. I'm a guest of the German sudoku championships in Dusseldorf, so I wanted to do this special price to the best German player. I think he deserves it, winning his 1rst test on LMI. This can perhaps explain the fact that there are 3 German players (it's well-known that German people like beers, ) in the top 10
Tiit played just few hours after becoming Estonian sudoku champion ! Congrats !

Thanks to Deb and LMI team to have hosted this test and the great work they do for the puzzle and sudoku world !

I have to apologize: the test was harder than what I thought. Initially I sincerely thought that 5-10 players can complete the test. Now I can see how the sentence in th IB: "It is expected that top players will be able to solve all sudokus earlier than 120 minutes." was a bit pernicious and could have created some discomfort while playing.

My mistake was to have asked only one tester for the points distribution.
Initially, Bastien tested 13 grids, with the untouch posted on my blog, which is a ~10 minutes grid for a top player. The 1rst version of the pointing evens was harder, also a ~10 minutes grid.
Bastien's sum of individual times was around 120 minutes, So I decided to work on the pointing evens, so that it'll be easier, and not putting the untouch. So the sum of individual times of Bastien was around 105 minutes. I know that the sum of individual times is not the reality of the competition, but he said to me that he hasn't played for 3-4 months (since WSC), so I thought that the global difficulty of the test was now ok. I must say 2 things:

-well, without playing 3-4 months, Bastien seems to be always very competitive
-It's been long time now that Bastien and me work together, testing each other grids for tournaments, for publications, etc... So he knows my work very well, which eventually gives him an advantage...

Well, I want that you understand well my comments: the difficulty of the test was not the fault of the tester, and I want to thanks Bastien here for having tested these grids !
(His time on the argyle was really 4'04. With more testers, perhaps this grid would have more points).

I'll not do a psychoanalysis to understand why I created so difficult grids, haha. But just a few notes:

-Normally I like when there are a few (1 or 2) hard grids, giving really some works for the top players. Easy grids are ok, but when a test contains only easy grids, I find that it's a speed contest, just playing very fast, and this real logical work finally miss. I see now that there were too much of these grids in the test: of course arrows battle, diagonal skyscrapers, diagonal consecutive (I'm not fast on these grids and generally on consecutives, seeing the results of the recent Krtek's round on fed-sudoku shows that the timings of best players are significantly better than mine, so this let me thought that this grid was hard, but ok), diagonal twin, and to a lesser extent Queen and antidiagonal.
-I created the test grids in november, just after the WSC, where my result was not really good. Unconsciously, perhaps I lost confidence on my sudoku solver's skill, and it pushed me to create hard grids ("if it's hard for me, it doesn't mean that it's hard for top players"). But I don't want to go further with these psychological considerations, haha



Prasanna, in my point of view, your role in taking the test few hours before others is not to evaluate the difficulty of grids. Even if you did a poor results, it was not the time to change the grids . I see your role more as the last check that everything works well, and eventually the last occasion to see if there is a problem with one grid (multi solution, or no solution). Thanks for having played this role and congrats for your very good performance.

I promise that the next test I'll author will be much more easier. Grids are already created and tested: it'll be a swiss qualification tournament, which will be hosted by the German LogicMastersDeutschland site. I'm not sure that a swiss player can finish all grids in time, but I'm sure that lot of international players can do it

Fred

Wonderful summary Fred. I'll try my best to make it for the next competition you say you've authored. I have a whole bunch of important exams coming up though so can't really be sure of anything.

As for the role of the tester, that is true, but I suppose if there was a more accurate view of my level globally, we could probably have stopped that sentence in the IB which has caused a bit of a problem. Thats all :) Thanks, I do like testing before time, since I rarely ever get time on weekends for anything

deu posted an interesting statistics in his blog - This is the only the second LMI monthly test where there is no players from Japan in top 10 (the first one being the very first monthly test Master Mind Twins almost 2 years back).

---

flooser won an LMI test first time. His previous best rank was 9 (incidentally another Fred's test). Some other players improved their best rank too (list below has only rank <= 20)

Player	Rank in Diagonal Vision	Previous Best Rank
flooser	1	9 (LMI Spring Sudoku Test)
sinchai4547	4	6 (Crazy Arrows)
tomek_s	6	40 (LMI April'2011 Sudoku Test)
smat	9	18 (Shapes and Sizes)
prasanna16391	15	28 (Best of LMI Mocks)
EKBM	17	41 (Best of LMI Mocks)

My main problem in this test is that the hard parts of the grids were all in the opening steps, even for the easier grids. So if you don't see the opening steps, you can't make any progress at all. There's a difference between a hard step when you have 25 digits in the grid or 45 digits in the grid. I had all these empty grids constantly where I was just looking for an opening which I couldn't find. It feels a bit frustrating to not be able to put any digits in. How much earlier the trickiest step is, the bigger the variation in solving times will be.
I started with the Argyle and couldn't solve it logically, which is why it took me almost 20 minutes to even submit a single grid after I decided to give up on it for now and go solve the diagonal instead.

They were nice puzzles, I just got stuck without making even a decent start too much, which was frustrating. My favourites were the Queen and Pointing Evens as I actually solved those 2 in a good flow, many of the others it took me too much effort to start.

Bram, you're right about the opening of several grids. I think that I like these hard openings. When a grid is already half-solved and need a hard step to be finished, I think it's easier to bifurcate and to finish the grid without taking the hard (but perhaps interesting) logical step. When it's in the beginning of the grid, I think it has better chance to showcase solver's skills. But of course, it creates lot of discomfort if you don't see it !

Abour argyle: I'm sure a player like you is able to solve this grid logically. It really solves without real hard steps. Perhaps you missed a naked single or a pair in a marked diagonal, I think these are the hardest steps needed to solve this one. The opening of this one is not hard, one can complete almost fully boxes 4-5-6 without any effort. After that there are a few things to see, that's right...

I'll perhaps post some explanations in the coming few days about some grids, especially the openings (diagonal, creasing, twins, little killer...).

Fred