Suji: Difference between revisions

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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 [[chiitoitsu]] are immune to suji.
Suji relies on the fact 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. For example, 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.


Not all suji are equally safe. This is because some tiles can be targeted by [[penchan]] or [[kanchan]].
Not all suji are equally safe. This is because some tiles can be targeted by [[kanchan]] (24) or [[penchan]] (12) waits.
*Suji terminals (1 and 9) are the safest, as they can only be targeted by a [[tanki]] or [[shanpon]].
*Suji terminals (1 and 9) are the safest, as they can only be targeted by a [[tanki]] or [[shanpon]].
*Suji 2 and 8, as well as a completed nakasuji (4,5,6), are the next safest. They can be targeted by a tanki, shanpon, or kanchan.
*Suji 2 and 8, as well as a completed nakasuji (4,5,6), are the next safest. They can be targeted by a tanki, shanpon, or kanchan.
*Suji 3 and 7 are the most dangerous, though still reasonably safe. They can be targeted by a tanki, shanpon, kanchan, or penchan.
*Suji 3 and 7 are the most dangerous, though still reasonably safe. They can be targeted by a tanki, shanpon, kanchan, or penchan.
 
*"Half suji" tiles, e.g. a 4 after only a 7 has been discarded, are not much safer than a regular tile.
"Half suji" tiles, e.g. a 4 after only a 7 has been discarded, are not much safer than a regular tile.


Suji based off the riichi declaration tile is considered to be more dangerous than normal. This is due to the strength of a ryankan shape. See the [[#Offense|Offense]] section for more information.
Suji based off the riichi declaration tile is considered to be more dangerous than normal. This is due to the strength of a ryankan shape. See the [[#Offense|Offense]] section for more information.
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===Checklist===
===Checklist===
For defense, eighteen different suji are in consideration as listed above.  Six basic suji multiplied by the three suits produces the count of eighteen suji. By counting the number of visible suji, players can determine roughly how risky it is to discard a dangerous tile.
For defense, eighteen different suji are in consideration: there are six basic suji for each suit, and three suits total. By counting the number of visible suji, players can determine roughly how risky it is to discard a dangerous tile.


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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. Basically, as more tiles become safe, the more dangerous the non-safe tiles become.
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, 4-7 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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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 would not discard any non-suji unless you had to.  
*If you were folding, you would not discard any non-safe non-suji tiles 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, ura suji assumes your opponent 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 completed 556 shape, or part of a completed 135 shape, and so on.
In addition, ura suji assumes your opponent 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 completed 556 shape, or part of a completed 135 shape, etc. Finally, the opponent could've completed the 23 before


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