Tuesday, 14 February 2012

Riichi theory(2): Side-effects of riichi

Source: http://blog.jpmahjong.net/read.php/610.htm

Previously we mentioned the various advantages of riichi. This time will be about the disadvantages and restrictions.

1. Decrease in winning rate
Yes, it's is a well known fact that the winning rate after declaring riichi is lower than damaten.
The rate of success of riichi over 60% in ordinary games, whereas it's around 45% in phoenix games. While damaten ryanmen waits have a 60-80% chance of winning, as long as not many discards have been made. Riichi's winning rate is around 60% of damaten.
However as the value of riichi hands are two to three times of the original value, in addition to having a high chance of tsumo, the expected value of riichi hands is much higher than damaten.

2. 1000 points expenditure
In most situations, the 1000 point fee of riichi is no big deal. However if everyone has a small deviation in points, you might want to take it into consideration.

3. After declaring riichi, all tiles must be discarded unless it's the winning tile or a tile that you can make ankan with
Riichi is a hand exposing declaration. After declaring riichi, you cannot change your tiles in order to change your wait or increase it's value.
Also, even if you draw a dangerous tile, you must discard it.
In superior level games, examples of dealing ins are often after declaring riichi.

In summary, the reason why riichi is a main attacking method in Japanese mahjong is because it's advantages far outweigh it's disadvantages.
Naturally, the advantages and disadvantages are affected by different hands and points situations. This is the basis of whether or not to declare riichi.

However, I can first tell everyone two very important points.
1. In Japanese mahjong, situations where you need to be in damaten is very rare.
2. You lose more points by not declaring riichi when you should than declaring riichi when you shouldn't.

Next, the following articles will discuss these three areas:
1. Hands which you should declare riichi and hands which you should be in damaten for
2. Standards of riichi, tesuji etc
3. Summary of riichi judgement

To be continued.

No comments:

Post a Comment