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Suji (view source)

Revision as of 04:50, 30 March 2024

370 bytes added ,  30 March
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(suji) checklist -> suji counting (which is probably more the more common name in english)
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m ((suji) checklist -> suji counting (which is probably more the more common name in english))
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*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.
*Therefore, if a tile in a suji interval is discarded, then other tiles in that interval become safer against that player. For example, if an opponent discards a 4, then the 1 of the same suit is safer. This is because, if they had an open wait, it would be subject to furiten. Similarly, the 7 also becomes safer when a 4 is discarded, due to the 4-7 interval.
*Therefore, if a tile in a suji interval is discarded, then other tiles in that interval become safer against that player. For example, if an opponent discards a 4, then the 1 of the same suit is safer. This is because, if they had an open wait, it would be subject to furiten. Similarly, the 7 also becomes safer when a 4 is discarded, due to the 4-7 interval.
*However, if a 1 is discarded, 4 does not become safer. This is because there are two different intervals for 4, that being 1-4 and 4-7. In order for 4 to be a "full" suji, both 1 and 7 have to be discarded. The same applies to 5 and 6.
**However, if a 1 is discarded, 4 does not become safer. This is because there are two different intervals for 4, that being 1-4 and 4-7. In order for 4 to be a "full" suji, both 1 and 7 have to be discarded. The same applies to 5 and 6.


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. So 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. So if an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are still considered suji.
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Suji relies on the fact that a player is likely to use 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 that do not use ryanmen, like [[toitoi]] and [[chiitoitsu]], are immune to suji.
Suji relies on the fact that a player is likely to use 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 that do not use ryanmen, like [[toitoi]] and [[chiitoitsu]], are immune to suji.


As mentioned above, the middle tiles (4,5,6) have two suji intervals to account for. For example, a 4 has two suji in 1-4 and 4-7. A discarded 1 does not make 4 much safer. In order for 4 to be a "full" suji, both 1 and 7 have to be safe.
As mentioned above, the middle tiles (4,5,6) have two suji intervals to account for. A 4 has two suji intervals, 1-4 and 4-7. A discarded 1 does not make 4 much safer, because an opponent could still have a 4-7 ryanmen wait. In order for 4 to be a "full" suji, both 1 and 7 have to be safe.


Not all suji are equally safe. This is because some tiles can be targeted by [[kanchan]] (24) or [[penchan]] (12) waits.
Not all suji are equally safe. This is because some tiles can be targeted by [[kanchan]] (24) or [[penchan]] (12) waits.
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*"Half suji" tiles, e.g. a 4 after only a 1 has been discarded, are not much safer than a regular tile.
*"Half suji" tiles, e.g. a 4 after only a 1 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.
Non-terminal suji based off the riichi declaration tile is more dangerous than normal. This is partly due to the strength of a ryankan shape. Ryankans are shapes like 135 or 468. These shapes are often kept for a long time for [[tile efficiency]] reasons. When reaching tenpai with a ryankan incomplete, a tile has to be discarded, e.g. 135 discarding 5 to wait on "suji" 2. Therefore, a player relying on suji may deal in. (Note that suji 1 and 9 are unaffected by this, as they cannot be part of a ryankan.)


===28 Suji vs 456 Nakasuji Safety===
===28 Suji vs 456 Nakasuji Safety===
There are a few considerations about the relative safety of 28 suji and 456 nakasuji tiles.
Suji 28 and 456 nakasuji are about equal in terms of safety. There are a few considerations that make one more or less safe, though.


In a game without [[Dora#Akadora|red fives]], the 456 tiles could be seen as safer. This is because to have a kanchan on a middle tile, for example, a 4, they would have had a 135 shape in their hand. It's generally seen as better to wait with the 13 shape, since the 4 is more useful and less likely to be discarded, so a middle tile kanchan suji trap is slightly less likely for this reason.
In a game without [[Dora#Akadora|red fives]], the 456 tiles could be seen as safer. To have a kanchan on a middle tile, for example, a 4, they could have had a 135 shape in their hand. It's generally seen as better to wait with the 13 shape, since the 4 is more useful and less likely to be discarded, so a middle tile kanchan suji trap is slightly less likely


However, in a game with red fives, the player has an incentive to keep the red five. If they have a 135 shape, and the 5 is red, they would likely discard the 1 in order to keep the dora. Or, with a 246 shape, they could take the 46 shape and hope to win on the red five. 456 could be viewed as more dangerous in this ruleset, especially if you can't see the red five in the suit of your 2 or 8. As a side note, this is why the suji of a discarded red five is seen as especially safe.
However, in a game with red fives, the player has an incentive to keep the red five. If they have a 135 shape, and the 5 is red, they would likely discard the 1 in order to keep the dora. Or, with a 246 shape, they could take the 46 shape and hope to win on the red five. 456 could be viewed as more dangerous in this ruleset, especially if you can't see the red five in the suit of your 2 or 8. As a side note, this is why the suji of a discarded red five is seen as especially safe.
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The [[dora]] itself can also change things. If the 1 or 2 is dora, the player would generally want to keep the 13 shape for the value, while if the 4 or 5 is dora, they would want to keep the 35 shape. This applies to the other suji shapes as well.
The [[dora]] itself can also change things. If the 1 or 2 is dora, the player would generally want to keep the 13 shape for the value, while if the 4 or 5 is dora, they would want to keep the 35 shape. This applies to the other suji shapes as well.


===Checklist===
==Suji counting==
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.
"Suji counting" is a strategy which is not directly related to suji. It basically states: as more types of tiles become safe, the more dangerous the non-safe tiles become.
 
In practice, this can be achieved by counting the number of visible suji. When more tiles are applicable for suji, the non-suji tiles become more dangerous. Eighteen different suji are in consideration - six suji for each suit, and three suits total.  


{| class="wikitable"
{| class="wikitable"
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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, 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.
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.


== Offense ==
== Offense ==
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The strategy of suji may be used offensively.  By utilizing suji in reverse, a player may use a tile within an interval to lure out a winning tile along the same interval.  A defending player may presume a certain tile to be safe by suji, when it is actually not.  This is commonly known as the "suji trap".
The strategy of suji may be used offensively.  By utilizing suji in reverse, a player may use a tile within an interval to lure out a winning tile along the same interval.  A defending player may presume a certain tile to be safe by suji, when it is actually not.  This is commonly known as the "suji trap".


A common way for this to occur is when a player has a ryankan shape, such as 468. They can discard the 4 to wait on 7, which is suji of the 4. Other players who know about suji may see this and be more likely to discard the 7. This is part of the reason why the suji of the riichi tile is considered dangerous.
A common way for this to occur is when a player has a ryankan shape, such as 468. In this case, the opponent can discard the 4, and wait on 7. This takes advantage of other player's knowledge of suji.


== Other suji ==
== Other suji ==
Hordes
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