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Tori Shogi
2014-05-06, 03:58 PM
Post: #1
Tori Shogi
Is Tori Shogi still widely played in Japan, and does there exist an organization for it similar to the Chu Shogi renmei?

I have some doubts about the rules, in particular the repetition rule. The English Wikipedia states
Quote:if the same position occurs three times with the same player to play by repetition of moves, the player starting the sequence must vary the move.

This seems to imply that Oute Sennichite (perpetual check) would be a win for the checking side. Which is very unusual in Shogi. But when the loop of checks and evasions is entered by the checking side (which is usual), he can keep checking until the first checking position occurs for the third time. And then, if I understand the rule correctly, the side that is now in check would be forced to vary its move. Meaning he now likely must step with its King into check, as he is no longer allowed to play the only safe evasion, so that his King will be captured.

Can this be correct?
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2014-05-07, 12:36 AM
Post: #2
RE: Tori Shogi
I don't think it is widely played at all.
I did a quick search, and it seems this website is one of the most reliable ones.
http://www10.ocn.ne.jp/~cha/kotenyugi/to..._syogi.htm

(7) Repetition
In repetition, when the same position is about to appear for the third time, the player who first created that position must change his move before it appears 3 times. However, if that move is to remove a check, the checking player must change his move.
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2014-05-08, 07:09 PM
Post: #3
RE: Tori Shogi
Thank you very much!

The rule you quote is very different from that stated in English Wikipedia. In fact it seems the almost complete opposite: it puts the burden to prevent reaching the repeated position on the player that first created it, rather than putting the player in trouble that has to move out of it once it is repeated. This seems a much better rule, and in better agreement with other Shogi variants.

The exemption of check evasions is still needed to prevent the possibility to win by perpetuals: the normal situation with perpetuals is that the checking player jumps into the repetition loop by a checking move. At some point he would then have to stop his checking, because he cannot do it from the same position again. But then, after he plays another move, and the opponent a reply, both elsewhere on the board, the position is on a fresh perpetual-checking loop with the checking side to move, rather than the evading side. So the evading side would be first to recreate the position, and he would not have any alternative evasions available.

The rule you quoted actually seems to be the best of its kind. It does not require one to consider the entire loop to determine if one side is perpetually checking (as you need to do in Shogi or Xiangqi), and is conceptually very simple. Check evasions can repeat at will, other moves cannot.
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2014-05-09, 06:21 PM
Post: #4
RE: Tori Shogi
One thing not clearly stated in that page is, when does the checking player have to change his move. Is it BEFORE or AFTER the checkee (the opponent who is being checked) makes the 3rd-time repetition?
If BEFORE, the checking player must foresee 2 moves earlier, that his check will force (or allow) the checkee to make the 3rd time repetition, and has to change his move already.
What if he fails to change? Can the checkee then make the 3rd-time repetition, and is this a win for him???
Or maybe the checker must change his move RIGHT AFTER the checkee made the 3rd-time repetition?
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2014-05-10, 05:06 PM
Post: #5
RE: Tori Shogi
Hmm, good point. But I guess the fact that a second repetition is always allowed, should make this distinction not very important. This gives the checking player ample opportunity to change his play in any stage of the loop.

In WinBoard I now simply use the same method as it used in Xiangqi, which should be close enough: if the non-checking side is the first to create the non-allowed repetition, I don't adjudicate the game yet, but give the checking side one more opportunity to vary his play. Only if the checking side causes the non-allowed repeat, he forfeits immediately. The only difference is that this takes all moves of the repeat loop into account, to decide if there is perpetual checking, and not just the current one.

The fact that a first repeat is allowed does cause some other ambiguity, though: it is conceivable that a first repeat is reached 'voluntarily', i.e. without checking moves, and that subsequent repeats are then forced by checking. Now would this count as perpetual checking in Shogi? I asked prof. Takeshi Ito this in the context of mini-Shogi, and he was of the opinion that one should consider all moves since the first occurrence of the repeated position (and thus that the sketched case would not be perpetual checking), and not just the moves since the previous occurrence. In mini-Shogi this is a bigger deal than in regular Shogi, as not classifying it as a perpetual can actually cause it to be a win for the checking side (if that was Gote), while in regular Shogi it would be a draw (and thus the incentive of forcing it by checking would not be very large). But in theory the issue still exists.
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