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(nakasuji 4/5/6 is safer than suji 2/8. complete a sentence i forgot to finish. add a safety% section to defense, noting that you should not rely on suji for betaori) |
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'''Suji''' {{kana|筋}} is a [[defense|defensive]] tactic that uses the [[furiten]] rule to determine which tiles are safer against a specific opponent. When a tile is suji, a it is impossible for an opponent to have a [[ryanmen|certain type of wait]] without being in furiten. It only applies to number tiles ([[manzu]], [[pinzu]], [[souzu]]). | '''Suji''' {{kana|筋}} is a [[defense|defensive]] tactic that uses the [[furiten]] rule to determine which tiles are safer against a specific opponent. When a tile is suji, a it is impossible for an opponent to have a [[ryanmen|certain type of wait]] without being in furiten. It only applies to number tiles ([[manzu]], [[pinzu]], [[souzu]]). | ||
When using suji, it is helpful to know the "mahjong intervals" of 1-4-7, 2-5-8, and 3-6-9, as shown in the picture to the right. | When using suji, it is helpful to know the "mahjong intervals" of 1-4-7, 2-5-8, and 3-6-9, as shown in the picture to the right. Suji will group | ||
==Basic Theory== | ==Basic Theory== | ||
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===Why suji works=== | ===Why suji works=== | ||
Suji defends against [[ryanmen]] | Suji defends against [[ryanmen|open]] [[wait]]s <small>([[ryanmen]] wait)</small>. An open wait is a wait that wins off two sides of a sequence, e.g. a hand containing {23}, or a hand containing {34}. | ||
*The most common type of wait is an | * The most common type of wait is an open wait, which appears in ~50% of all winning hands, and ~58% of all [[riichi]] hands.<ref>Riichi hands: https://docs.google.com/spreadsheets/d/1x1CYlIPYTeOodGY4bmPevlbyeZOIcmHICcQaoSjHJEk/edit?gid=295861978#gid=295861978</ref> | ||
*[[ | * [[Sequence]]s are comprised of three sequential tiles, so an open wait always will win off two tiles that are 3-apart. For example, a {23} ryanmen can win off either a 1 or 4 of the same suit. {34} can win off a 2 or 5 of the same suit. This continues until you get the intervals of: 1-4, 4-7, 2-5, 5-8, 3-6, and 6-9. | ||
*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. | ||
*Therefore, if every tile in a suji interval is discarded, then the other tile in that interval become safer against that player. | * Therefore, if every tile in a suji interval is discarded, then the other tile in that interval become safer against that player. | ||
**If an opponent discards a 4, it is ''impossible'' for an opponent to have an open wait on 1 (without being in furiten). There is only one interval for the 1, that being 1-4, which is eliminated. Therefore, the 1 is safer against that opponent. Likewise, the 7 becomes safer when a 4 is discarded, due to the 4-7 interval being impossible. | ** If an opponent discards a 4, it is ''impossible'' for an opponent to have an open wait on 1 (without being in furiten). There is only one interval for the 1, that being 1-4, which is eliminated. Therefore, the 1 is safer against that opponent. Likewise, the 7 becomes safer when a 4 is discarded, due to the 4-7 interval being impossible. | ||
**If an opponent discards a 1, it is not impossible for an opponent to have an open wait on 4. There are two different intervals for 4: 1-4 and 4-7. After discarding a 1, an opponent could still have an open wait on 4-7 interval. In order for the 4 to be a "full" suji, both 1 and 7 have to be discarded. The same logic applies to tiles numbered 5 and 6. | ** If an opponent discards a 1, it is not impossible for an opponent to have an open wait on 4. There are two different intervals for 4: 1-4 and 4-7. After discarding a 1, an opponent could still have an open wait on 4-7 interval. In order for the 4 to be a "full" suji, both 1 and 7 have to be discarded. The same logic applies to tiles numbered 5 and 6. | ||
Note: suji applies to the other forms of furiten, not just discard furiten. So long as a tile is [[genbutsu]] (an opponent would be furiten if they were waiting on that tile), then the suji of that tile are safe. Most importantly: after an opponent declares [[riichi]], then any non-winning tile discarded by anyone becomes safe through furiten. Therefore, suji can also be applied to those discarded tiles. So if an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are considered suji against the riichi-declarer. | Note: suji applies to the other forms of furiten, not just discard furiten. So long as a tile is [[genbutsu]] (an opponent would be furiten if they were waiting on that tile), then the tiles within "suji interval" of that tile are safe. Most importantly: after an opponent declares [[riichi]], then any non-winning tile discarded by anyone becomes safe through furiten. Therefore, suji can also be applied to those discarded tiles. So if an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are considered suji against the riichi-declarer. | ||
==Intervals== | ==Intervals== | ||
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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. | ||
*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, | * Suji 2 and 8, and "full" 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. | ** Nakasuji 4/5/6 are safer than suji 2/8. | ||
*"Half suji" tiles, e.g. a 4 after only a 1 has been discarded, are about as safe as a non-suji 2 (which is not safe). | * 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 1 has been discarded, are about as safe as a non-suji 2 (which is not safe). | |||
Non-terminal suji based off the riichi declaration tile are 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.) | |||
=== | === How safe are suji? === | ||
Assuming its turn 8-12, and no other factors are in play:<ref>https://pathofhouou.blogspot.com/2020/05/analysis-tile-deal-in-rates-by-live-suji.html</ref> | |||
* Suji 1/9 is about x25% as dangerous as a non-suji 1/9. | |||
* Suji 3/7 is x50%-x60% as dangerous as a non-suji 3/7. | |||
In | Against a turn 1-2 riichi, suji is ineffective since players are less likely to have a ryanmen wait. In the late game (turn 12+), non-suji tiles become relatively more dangerous due to the effect of [[#Suji counting|suji counting]], though suji tiles also become more dangerous in the late game. | ||
Since suji is up to 60% as dangerous, you should not depend on suji if you are planning to [[betaori|fold completely]]. Suji is best used if you have no other safe tiles, or when planning to use [[mawashi]]. | |||
==Suji counting== | ==Suji counting== |
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