Saturday, 18 February 2012

Riichi theory(3): Pre-emptive tenpai hand with good shape


For the next three articles, I'll be introducing some commonly seen hands that you should declare riichi with and some hands that you should be in damaten for. Today will be concentrating on hands with tenpai waiting on ryanmen or above. The reader must note that the discussion here is assuming that no other player is attacking. (riichi, in tenpai with multiple exposed melds) To decide whether or not to declare riichi while an opponent is attacking, you should use the offence and defence judgement that was previously mentioned as a baseline.

All ryanmen tenpai should declare riichi, except for some special situations.
This is the tesuji of modern mahjong.

Then what are the "special situations"?

1. Hands with value haneman and above
The most commonly seen ones are either menzen chinitsu or honitsu. 

Hands with value haneman and above should be in damaten. The reason is that the 1 han from riichi has little effect here, even not having any value. Your winning rate goes down after declaring riichi, therefore there's no benefit here.

Then, what about mangan tenpai?

With a hand with 7700 points, riichi's effects are smaller than a 1 or 2 han hand. If everyone has the same points, you can be in damaten to quickly take the lead. But if it's still early, the chances of winning is huge. Or if someone declares riichi, instantly declaring riichi to gamble for a haneman is also a viable choice.

2. All last and not needing the extra points to reach first place
This shouldn't need any explanation. (smile)

Basically, these should be all of the special situations.
Then does it mean that all the other ryanmen tenpai should declare riichi? Theoretically, that's correct. In a game between advanced players, a pre-emptive riichi is very powerful. Beginner advanced players(especially those around Tenhou's higher level tables) do not dare to declare riichi, crippling their firepower. The following shows a few common examples:

Pinfu dora 1
Beginner advanced players like sanshoku too much, and many of them stay in damaten for a hand like this.

There are people who stay in damaten just to wait for 7 sou. This type of hand is definitely a bad hand.
It's true that this hand is at least 7700 points if you draw 7 sou, however the problem is that the chances of someone discarding 14 pin or drawing them yourself is much higher than drawing 7 sou. (The former has 8 tiles, while the latter has 4 tiles.) The result is that hands like this often end up with damaten 2000 points or tsumo 700-1300 points. This is a huge waste. A instant riichi might not let you change tiles if you draw 7 sou, but if someone discards 14 pin, then you'll at least get 3900 points. Not only that, there's also a one in three chance of getting ura-dora, thus increasing the points to 7700 points which is equivalent to damaten pinfu sanshoku. Immediately declaring riichi has a chance of getting mangan, which is not lower than drawing 7 sou and then staying in damaten. With the various benefits of riichi, it's more advantageous to just declare riichi.

What about this kind of hand?

A hand that is at least 2000 points and as high as 7700 points. Many people will stay in damaten but you should instantly declare riichi with this kind of hand.
After declaring riichi, even if the yasume appears, there's still a good chance of getting ura-dora and turning the hand into a mangan, and even having a chance of becoming haneman if the takame appears. Drawing the yasume while in damaten is the real tragedy here.
No matter if the takame is on the inside or the outside, you should immediately declare riichi with this kind of hand.

Applying the same logic, you should not wait for ittsu with the hand below but declare riichi immediately.

An instant riichi with pinfu dora 1 is the basic among the basics.

Pinfu-nomi/No yaku ryanmen wait
Then what about pinfu nomi or a no yaku ryanmen wait?

The mainstream theory in the old days prefer damaten. The reason is that it's unreasonable to spend 1000 points to reach 1300/2000 points. However in today's time, this theory is outdated. This two types of hand are immediately declared riichi with.

Using pinfu nomi as an example, riichi pinfu is only 2000 points on the surface. However, if you include ippatsu ura-dora etc, the average points of pinfu nomi is above 3000 points. Added to the fact that opponents cannot freely make discards, declaring riichi is advisable.

Also, when we're in ryanmen wait, we'll rarely consider changing tiles.

Even if you can have tanyao by drawing 36 wan, or dora by drawing 7 sou, you should instantly declare riichi with this kind of hand. Half of the time after tenpai, winning happens within 5 rounds of discards. Even if you have 12 effectives tile, you'll still need 7-8 rounds of discards to draw it. Therefore in many instances, you'll find that before you draw your effective tile, you would already be able to win. This directly affects your scoring ability.

Pinfu dora 2
I've seen people who advocate damaten with pinfu dora 2 in some forum.

An instant riichi with pinfu dora 2 is better. It's at least 7700 points with riichi, there's also a better chance of tsumo haneman. There's a huge difference compared to winning 3900 points with damaten.

The only acceptable example is the dealer nearing ryuukyoku with a 5800 points tenpai. When the number of round of discards left is not much, maximizing your chances of winning to achieve renchan is a logical method, even though the points is not much. However, immediately declaring riichi is not a bad choice either.

Is the current round of discard related?
The aforementioned riichi standard should not be affected by the current round of discard. You should just declare riichi with pinfu dora 1, regardless of whether it's the 1st round or the 15th round. It's true that your chances of winning is low when you're close to ryuukyoku. However, do not forget that the success rate of damaten is also limited. Riichi also has the ability to cause other players to go into betaori, earning you the noten bappu. This is also riichi's intangible advantage.

In summary, you don't need to consider the current round of discard or tiles changing with pre-emptive ryanmen. There's nothing wrong with an instant riichi.

The next time will be discussing examples of tenpai with bad shapes.


  1. Ah, this was very helpful... I've made some of the mistakes described on this page. Thanks for the translation. :)

  2. I wonder if in the JPML-A rules there are more situations where you shouldn't declare riichi since there's no ippatsu nor ura dora.

    1. Well, in that case I would be more hesitant in declaring riichi. I wouldn't know what the author would do though.