Suji: Difference between revisions

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fix chiitoi spelling, minor "basic theory" adjustment, ura suji adjustment
m (fix chiitoi spelling, minor "basic theory" adjustment, ura suji adjustment)
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*[[Shuntsu|Sequences]] are comprised of three sequential tiles. Therefore, an open wait will win off two tiles that are 3-apart. For example, {23} can win off either a 1 or 4 of the same suit. {34} can win off 2 or 5 of the same suit. This continues until you get the intervals of: 1-4, 4-7, 2-5, 2-8, 3-6, and 3-9.
*[[Shuntsu|Sequences]] are comprised of three sequential tiles. Therefore, an open wait will win off two tiles that are 3-apart. For example, {23} can win off either a 1 or 4 of the same suit. {34} can win off 2 or 5 of the same suit. This continues until you get the intervals of: 1-4, 4-7, 2-5, 2-8, 3-6, and 3-9.
*Due to the [[furiten]] rule, if a player has previously discarded any tile they could have won off of, they cannot win from other players.
*Due to the [[furiten]] rule, if a player has previously discarded any tile they could have won off of, they cannot win from other players.
*This makes suji helpful. For example, if an opponent discards a 4, then the 1 of the same suit becomes safer against them. If they had a wait that wins off the 1-4 interval (such as {23}), then it would be subject to furiten. Thus, in this case, they couldn't win off your 1 discard. Similarly, the 7 also becomes safer when a 4 is discarded, due to the 4-7 interval.
*This makes suji helpful. For example, if an opponent discards a 4, then the 1 of the same suit becomes safer against them. If they had a wait that wins off the 1-4 interval (such as {23}), then it would be subject to furiten (thus, unable to win off your discarded 1). Similarly, the 7 also becomes safer when a 4 is discarded, due to the 4-7 interval.


Note: suji also applies to the other forms of furiten. After an opponent declares [[riichi]], then any non-winning tile discarded by anyone becomes safe. Therefore, suji can be applied to these tiles as well. If an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are still considered suji.
Note: suji also applies to the other forms of furiten. After an opponent declares [[riichi]], then any non-winning tile discarded by anyone becomes safe. Therefore, suji can be applied to these tiles as well. If an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are also considered suji.


==Intervals==
==Intervals==
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== Defense ==
== Defense ==
Suji implies that a player is using a [[ryanmen]] wait, or a related wait like [[ryanmenten]], [[nobetan]], or [[sanmentan]]. Ryanmen itself appears in around ~50% of winning hands, which is common, but not even close to guaranteed. Hands like [[toitoi]] and [[chitoitsu]] are immune to suji.
Suji implies that a player is using a [[ryanmen]] wait, or a related wait like [[ryanmenten]], [[nobetan]], or [[sanmentan]]. Ryanmen itself appears in around ~50% of winning hands, which is common, but not even close to guaranteed. Hands like [[toitoi]] and [[chiitoitsu]] are immune to suji.


Note that the middle tiles (4,5,6) have two different suji intervals to account for. For example, 4 is part of the intervals 1-4 and 4-7. If an opponent discards a 7, the 4 isn't much safer, because the ryanmen of 1-4 is still present. In order to make 4 safer, both 1 and 7 must be safe. If both 1 and 7 are safe, then 4 is considered a nakasuji. The same applies to the other intervals.
Note that the middle tiles (4,5,6) have two different suji intervals to account for. For example, 4 is part of the intervals 1-4 and 4-7. If an opponent discards a 7, the 4 isn't much safer, because the ryanmen of 1-4 is still present. In order to make 4 safer, both 1 and 7 must be safe. If both 1 and 7 are safe, then 4 is considered a nakasuji. The same applies to the other intervals.
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Say an opponent declares riichi on [[double riichi|turn 1]], discarding an honor tile, and your turn is next. If we assume the opponent has a ryanmen wait, there is only a 1/18 chance that any one of the untested suji intervals deals in.  
Say an opponent declares riichi on [[double riichi|turn 1]], discarding an honor tile, and your turn is next. If we assume the opponent has a ryanmen wait, there is only a 1/18 chance that any one of the untested suji intervals deals in.  


If an opponent declares riichi after discarding 4-man, 2-pin, 6-pin, and 5-sou, then the following suji are safe: 1-4 man, 1-7 man, 2-5 pin, 3-6 pin, 6-9 pin, 2-5 sou, and 5-8 sou. This "eliminates" 8 suji intervals, leaving 10 intervals unaccounted for. Therefore, if we assume the opponent has a ryanmen wait, an untested suji has a 1/10 chance to deal in. As more tiles become safe
If an opponent declares riichi after discarding 4-man, 2-pin, 6-pin, and 5-sou, then the following suji are safe: 1-4 man, 1-7 man, 2-5 pin, 3-6 pin, 6-9 pin, 2-5 sou, and 5-8 sou. This "eliminates" 8 suji intervals, leaving 10 intervals unaccounted for. Therefore, if we assume the opponent has a ryanmen wait, an untested suji has a 1/10 chance to deal in. Basically, as more tiles become safe, the more dangerous the non-safe tiles become.


== Offense ==
== Offense ==
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=== Musuji ===
=== Musuji ===
Musuji {{kana|無スジ}} is a tile that is not [[genbutsu|100% safe]] and not suji.  
Musuji {{kana|無スジ}} is a tile that is not [[genbutsu|100% safe]] and not suji.


If an opponent discards multiple musuji tiles in a dangerous situation (e.g. after a riichi), then it's likely that they are in tenpai as well.
If an opponent discards multiple musuji tiles in a dangerous situation (e.g. after a riichi), then it's likely that they are in tenpai as well.
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In the modern day, ura suji is often disregarded. If an opponent discards 5-pin early, then declares riichi, then non-suji 4-pin would be a dangerous tile. However, a non-suji 4-man, 5-man, 4-sou, etc. would also be dangerous tiles. Therefore, knowing about ura suji would not change your behavior.  
In the modern day, ura suji is often disregarded. If an opponent discards 5-pin early, then declares riichi, then non-suji 4-pin would be a dangerous tile. However, a non-suji 4-man, 5-man, 4-sou, etc. would also be dangerous tiles. Therefore, knowing about ura suji would not change your behavior.  
*If you were folding, you wouldn't discard any musuji unless you had to.  
*If you were folding, you would not discard any non-suji unless you had to.  
*If you were attacking, you would discard ura suji anyways, because an ura suji is not that much more dangerous than a regular non-suji tile.
*If you were attacking, you would discard ura suji anyways, because an ura suji is not that much more dangerous than a regular non-suji tile.


In addition, it assumes your opponent is going for maximum [[tile efficiency]], and it also assumes that the 35 kanchan had existed in the first place.
In addition, ura suji assumes your tile is going for maximum [[tile efficiency]]. It also assumes that the 35 kanchan had existed in the first place. The 5-pin could have been an unrelated tile, or it could have been part of a 57 kanchan, or part of a 556 shape.


== External links ==
== External links ==
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