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Dr Muller, I read your very intriguing presentations of errata in the tsumechushogi problems from collections A, B, and C published in Middle Shogi Manual.  I have to wonder whether there are errata in collection D that your analysis has revealed and whether you would think such fine studies worthy to add to CVP.

@Bukovski:

Yes, I used my Chu Shogi engine to solve all 224 problems of the A-D series,or prove no solution exists. Series C and D were different from A and B in the sense that the historic documents from which they came containedno solutions. So all problems that were solved when the MSM was published were solved in recent times, and many were still unsolved. Of the latter, 14 problems of the D series could be solved, while18 were proven flawed.

So far I did not put the results of the D series on-line, to keep open the possibility to use them in contests. (I thought I had done the same with the C series,but apparently not.)

I put together my own Chu set based on the mnemonic pieces, by simply cutting their shapes from stickers, and stick those on Draughts chips. Two Draughts sets of 2 x twenty 35mm chips were used for the (32) pieces, while a set of smaller (29mm) chips was used for the Pawns and Go Betweens (14 chips used). The required board is 42 x 42 cm, and was simply drawn on four sheets of A4 paper.

Can someone please help me with a question regarding this rule?  I need an answer for a game in progress...

A Lion cannot capture a Lion if that would expose it to recapture in the next turn, as if it had become an absolute royal for one turn. ('protected')

My question is this: can a Lion make a 2-step move in which he captures the other Lion (which is protected!) with the first step, and then move to safety with the second step?

Thanks!

Yes,it is always allowed to capture an adjacent Lion. Even if it means your Lion can be recaptured afterwards.(Which you usually of course can and want to avoid.) In this case the recapture would also be legal.

Ok, next question:

If a Lion captures the opposing protected Lion by means of capturing a second piece first, is it then permissible to recapture the Lion, or does this rule prevent it?

A non-Lion cannot capture a Lion when on the previous turn a Lion was captured by a non-Lion on another square.

It sounds like this rule prevents it, but that seems crazy. 

The rule does not apply to your case for multiple reasons:

• It specifies what happens after a non-Lion captured a Lion, while your case starts with a Lion capturing a Lion
• The rule applies to what happens when the Lions are captured on different squares, while in your case the two Lions are captured on the same square.

So neither the protected-distant-Lion nor the counter-strike rule apply to this case, which by default means the recapture is allowed. There even is a special Japanese term for this, which translates as 'beating/shooting the Lion'.

BTW, the addition 'on another square' is there to handle the unique case of a Kirin (a non-Lion) capturing a Lion and promoting, so that the recapture now hits a Lion too. Recapture of this Lion would be allowed, while a counter-strike against a Lion elsewhere with a non-Lion would be forbidden.

Here's a set I made earlier so if people are looking for cheap ways to make a chi shogi set here's an idea. I drew the board but you can also use a 13x13 go board too. The counters cost me about £1.50? And I just wrote on them with sharpie.

It looks like you used a fake URL for your image. It literally says "fake-url" in it.

Oh it looked fine from my iPad? I pasted a photo into the comment. Is there a better way to do it?

Click on the image button and enter an URL to the image. It's to the right of the flag (Anchor button) and to the left of the graph (Table button) in the right center part of the top row. Or go to Source mode and directly enter HTML in the form of

<IMG SRC="image-url">

If you want to have the images hosted here (if they are just on your computer, not on the web yet and so have no URL), send them to me and I'll put them into the folders for the respective games.  (The text editor doesn't support uploading of images, AFAIK)

Here's a set I made earlier so if people are looking for cheap ways to make a chu shogi set here's an idea. I drew the board but you can also use a 13x13 go board too. The counters cost me about £1.50? And I just wrote on them with sharpie.

Hi,

I don't know if anyone has mentioned this yet, but the chu shogi preset is not working; I had a look, and the { } 's in the FEN code seem to have been replaced with their charachter codes, and when you click 'menu' from an already active game it seems to use the chess FEN code. I can't edit it because I didn't make it and the FEN code can't be changed via customize.

Would someone be able to check it out?

Thanks in advance!

sxg

These are mere presets that do not include settings files. I edited the HTML forms for the Chu Shogi presets to use FEN code that has not been URL encoded.

Dr Muller, you mention the bare king rule as used by the Nihon Chu Shogi Renmei, but I have to wonder if your computer analysis has revealed what pieces singly or in combination are sufficient to force or at least deliver checkmate on a bare king in chu shogi.

Only Pawn, Leopard and promoted Leopard cannot not force checkmate on a bare King. Many of the weak pieces lack mating potential, but against a bare King they should be easy to promote, and all promoted types except Bishop have mating potential. Because they virtually all have at least one orthogonal sliding move, and can move perpendicularly to that. That is all that is required, and makes the mate in fact quite easy (so that last century even a mechanical machine was built to do it!). The other exceptions are +P and +DE. As it turns out, Gold has no mating potential on 12x12 (it stops at 11x11), but DE and +DE still have (up to 14x14, IIRC, which would affect Dai Shogi). A Blind Tiger that cannot seek shelter with its King can sometimes be chased by the bare King to its back-rank, and get lost there. And Pawns approached from the front are doomed too, if the bare King gets there before yours.

The only pair of pieces without mating potential is a pair of +FL on the same 'square shade'. Provided none of them is trapped, which for two Pawns far away from each other can be a problem.

@Dr Muller: You had mentioned that you had analyzed the D document of historic chu shogi problems in MSM, had reserved the results of your analysis, and had concluded that 18 were proven flawed.  I wonder if you had reached a conclusion about the 18 like one that Mr Hodges proposed about the D document generally, that necessary pieces possibly had been omitted or erroneous pieces introduced into the diagram to act as a security device against plagiarism.  I read your suggested corrections to problems in the other 3 collections; I do not ask you to divulge more than you want about D, only to ask if your research suggested that the flawed problems might be fixed by the removal, change, or addition of pieces to the diagram.  Kind regards!

I have not really looked at those problems to see if I could find an easy flaw since I first analyzed them, and have been busy with other projects since.It seems a daunting task to figure out if the lack of a solution is due to a plausible oversight of the composer, and what he overlooked. I am not even sure how one would have to approach that problem. The computer just concludes whether there is a mate or not. It doesn't know the concept of 'nearly mate'. Because all the moves are checks it is not uncommon in problems that do have a solution that there is only a single legal move for gote in some positions, or only a single move that does not get him mated very quickly. So having only a single move to escape the mate in some variation doesn't really indicate the composer must have overlooked that move. (Ignoring the problem that the computer usually does not know there is only one refutation to the mate attempt, as it doesn't search any alternative moves once it finds the refutation. This could be solved by altering the program to require at least two refutations in each position, at the expense of driving the solution time up by a factor of 2^N for a mate in N full moves.)

It really requires human judgement to identify a move as a plausible candidate for being overlooked.

Perhaps the following would work: equip the program with a 'conditional exclude-move' option, through which you could tell it: in this position, you must consider that particular move as illegal. You could then start running the engine on the the flawed problem; it will find a principal variation that keeps up the checking as long as possible, but eventually it will run out of checks. You can then try to 'repair' the problem by 'outlawing' the gote moves in this PV one by one, starting at the end, and try to solve the problem for that case. If the outlawed move was the only move that escaped mate, the problem would then have a solotion, and the defensive move could have been the one overlooked by the composer. If the problem is still flawed, because gote has an alternative escape, we probably are already in a position that was never intended to occur.

About the strategy part of the article.

From the games I had played against user Dax00 it seems to me the advices here are not optimal although wikipedia states roughly the same things regarding the early moving up of steppers.

In our games dax00 has taught me to early lyon jump in front very early (the latest at turn 3) and then the stronger pieces take relevant forward positions until it becomes worthless for them to keep dancing around, and only then steppers (and maybe phoenix) kick in slowly but surely as the strong pieces are stuck in their duties :)!

What am I missing?

Getting a Lion out early is OK; it is impervious to stepper attack by its igui capability, and can easily withdraw when chased by sliders because of its jumping ability. And if the opponent develops his Lion, you often have no other way to keep it at bay than opposing it with your own Lion.

But suppose your opponent will keep his sliders safely behind his Pawn wall, and advances his Copper, Silver and Leopard while you are dancing around with your sliders. No matter how fast you develop your sliders, they won't be able to breach the Pawn wall, as this is well protected by the opponent's sliders without him having to spend many moves: his sliders start there. At some point the Silvers and Coppers stream out through the occasional hole in the Pawn wall, and will start forking your valuable sliders, which are trapped in the narrow area between the Pawn walls (usually both sides advance all their Pawns one step without opening up large holes, to allow the Side Movers to cover the original Pawn rank). You will get slaughtered.

Sliders are very valuable in Chu Shogi, because they promote easily in the end-game. Promoting steppers, OTOH is very difficult: they need to approach from afar, and by the time they reach the zone the opponent will oppose them with his steppers, needing far fewer moves to do that. And you have to overcome the extra defense provided by his Side Movers; you cannot neutralize those with your own Side Movers. Basically you can only promote steppers that are left over when all stepper material of the opponent has been traded away. So if there is an imbalance where you have steppers, and the opponent tactically equivalent sliders, and the potential promotion gain is the same, you are toast: he will promote all his sliders long before you promote your first stepper, and this will put you at such a tactical disadvantage that you will not have any steppers left by the time the opponent has not enough material left to prevent them from entering the zone.

In warfare one should never expose one's artillery to infantry attack!

Ok, HG,  thanks!

When I try to promote a Dragon King, it promotes to a Tokin instead of a Soaring Eagle. However, this can be easily fixed by making the King the last piece and changing the parameters accordingly.

Is there a new enforcing preset I'm unware of?