Riichi strategy: Difference between revisions

Calling [[riichi]] comes with various considerations. While riichi does give a high score bonus, it also alerts players that you are in tenpai, and prevents you from [[defense|defending]]. Therefore, some discretion should be used before declaring riichi.

== Assessing riichi ===

[[Image:Indefensible riichi.png|thumb|right|250px|Riichi does not let you respond to [http://tenhou.net/0/?log=2012111209gm-0009-7447-x33034e7e5279&tw=2&ts=4 any conditions that change in the future].]] <!--Aligns with the disadvantages section better here-->

* Riichi is a [[yaku]]. It grants 1 additional han and allows any closed hand to meet the yaku requirement.

* By rule, the hand is locked. Therefore, it is impossible to change the composition of the hand in order to get a better wait or an improved score.   

There is a big advantage to being the first to tenpai, and thus an advantage to being the first to riichi.

* Only one hand can win per round. Winning first will prevent anyone else from winning.

* To complete a [[sequence]], a tenpai hand can call [[ron]] from anyone. Regular hands are stuck with [[chii]], which can only be called from the leftmost player.

** If an opponent decides to push: progressing from [[iishanten]] to [[tenpai]] is slow. Even with great [[tile acceptance]], going iishanten -> tenpai can take a few turns - this gives you a few turns to win.

** If an opponent decides to fold: great - that's one less opponent to worry about.

** In a ruleset with 3 [[red five]]s, an average riichi is worth 7000 points (though this considers [[menzen tsumo]]). From an expected value standpoint, pushing an iishanten isn't wise unless the hand is very good.  

Due to these advantages, a "head start" riichi is very powerful. Even if an opponent attacks into your riichi, you have chances to win before then. Declaring riichi ''just'' for intimidation is not effective, but any sort of value can make the riichi powerful.

Conversely, a chasing riichi (riichi after another player has declared riichi) is weaker for the same reasons. You should not shy away from chasing riichi, though; if you want to attack against an opponent, you want all the value you can get.

Once a hand reaches tenpai, its chance of winning depends largely on its [[wait]]s. The more tiles it waits on, the better. Since most of riichi's downsides only apply if you don't win, having a good wait (2+ sided wait, >=6 tiles acceptance) makes the riichi stronger. Conversely, a bad shape riichi is less likely to win, and may want to upgrade into a better wait.

[[Furiten]] weakens the hand. A furiten 2-sided wait ~= a non-furiten 1-sided wait. A furiten 3-sided wait is quite strong.

Riichi gives 1 han, and possibly more via ippatsu and ura dora. Every han doubles score until the [[mangan]] cap, so these are all valuable. If a hand is below mangan, riichi roughly ''triples'' your average score.

* Past [[mangan]], each han has reduced effectiveness. A [[haneman]]-or-higher hand shouldn't riichi because it is already very valuable, so the score bonus from riichi isn't as impactful. (Going from 6 han -> 7 han doesn't increase score. 7 han -> 8 han is only a +25% boost to score.)

* When first with a large lead, or first during [[all last]]. In this case, damaten helps increase your win rate, allowing you to end the game faster.

* When in [[all last]], where both dama and riichi will result in the same final placement (even with a direct hit riichi + 1 ura dora).

Pressing players to defend will often lower your chance of winning. When a hand has a yaku other than riichi, declaring riichi generally lowers your winrate by around x70% to x80%.<ref>Miinin. ''Statistical Mahjong Strategy''.</ref> Riichi more-than-doubles your score (before mangan), so it is much stronger under normal circumstances. If you don't care about the point boost, though, then dama is better.

{{Main|Situational analysis|Kyoku}}

[[Situational analysis]] (analysis of point standings/placements/round #) is key to using riichi. In the first half of the game, the exact point standings won't be a concern. There are many opportunities to make up differences: a player who's ahead can hardly afford to rest on their laurels, while players who are behind are not as desperate. Thus, playing for expected value is strong, even with a big lead.

In the latter half of the game (usually in the South round; can be earlier if a player is close to bankrupting), the point standing matters more. Most mahjong games include [[uma]], providing a huge incentive to rise/keep placements. Going from 3rd to 2nd is a major jump, and going from 3rd to 4th is a major blow. Even a +1000 point win is valuable if it causes you to rise in placement, or lets you keep your current placement. In the South round:

* Players that are ahead / in the lead should be more willing to dama. Late in the game, increasing your point lead doesn't matter as much, but the risk of dealing in matters more. Also, as mentioned above, dama increases your winrate, allowing you to end the game faster.  

* Players in 4th by a large amount are often forced to riichi, hoping for a big hand.  

* Players in the middle should analyze their own specific situations to determine if riichi is right. If being in 4th place confers a huge penalty (such as high ranked gameplay in [[tenhou.net]] and [[Majsoul]]), players not in 4th may want to dama to end the game faster, even if riichi could let them rise a place.

 

Overall: in the earlier end of the game, going for expected points can be a good idea. In the later end, aiming to retain (or improve) your placement usually matters more than the points themselves. This consideration will depend on the game's [[oka and uma]] settings.

By declaring riichi, the hand is locked - you cannot upgrade the hand to improve the wait, gain yaku, or play defensively.  

Note: when you reach tenpai but are waiting for an upgrade, it's often best to stay at [[iishanten]], ''unless'' you have an expensive hand (3+ han). If you enter tenpai with a 46-pin middle [[kanchan]], you have 8 tiles worth of upgrade. If you decline tenpai, you'll often have more than 8 tiles to upgrade with. For example, if you discard 6-pin, leaving 4-pin and a 2334-man shape, you have 18 tiles worth of non-furiten uprades.

The hand lock prevents you from defending, which is the biggest risk of declaring riichi. Often, the reward is worthwhile: even without riichi, it is often best to keep tenpai instead of defending. But if the risk of dealing in is greater than riichi's extra value, then it can be a bigger point of concern.

* Damaten has better control over [[takame and yasume]]. A dama hand can choose to reject a lower-scoring tile. However, since riichi is worth 1.5 han on average, the difference between takame/yasume needs to be 3+ han in order to matter.

* A damaten hand can try and target a specific player. You may want to ron to get a player below 0 points, ending the game immediately. Or you may wish to avoid calling ron on a player with 0 points, to not end the game. This can also be done to [[gyakuten|change placement]] when near all last (e.g. targeting 1st place as 2nd). However, since riichi gives a hefty point bonus, a riichi hand might improve your placement even if you tsumo or ron the "wrong" player.

Players often declare chasing riichi when:

* They have no option to defend.

* They have a strong hand. If hit tenpai with a good wait, and chase an opponent's riichi, your win rate far exceeds the deal-in rate.

 

When you do have the option to defend, the decision to push or fold should depend more on [[shanten]], [[tile acceptance]], and wait rather than the value of the hand.