Riichi or Damaten? (1)
Last time we listed the advantages and disadvantages of riichi.
But the advantages are overwhelmingly larger, so it is perfectly fine to think of "riichi when you reach tenpai" as the default rule.
Choosing damaten is the rarer case.
So the better approach is to remember the situations where damaten is stronger,
and in all other cases, riichi without hesitation.
There are two main materials for deciding between riichi and damaten:
the hand itself, and the situation.
(In mahjong, almost every judgment revolves around these two things.)
Hand: the wait, the value, and other factors inside your hand
Situation: current score, opponents' actions, turn count, and so on
Let us first think only about judgments based on the hand itself.
For now, assume the following:
- It is East round
- Scores are even
- The hand is still early
- No opponents have shown any action
This kind of situation is often called a neutral table.
Example 1
The clearest kind of damaten case is a yakuman hand like Example 1.
Riichi does not increase the score, so there is no reason to declare it.
The one exception is Suuankou that can still be won by tsumo. There, riichi is fine.
Example 2
If you already have a baiman hand with a yaku in damaten, you absolutely should not riichi.
There is a three-han gap between baiman and sanbaiman, and the chance that riichi pushes the hand all the way to sanbaiman is low.
Damaten is already more than enough as a decisive hand.
Lowering your ron rate just to riichi is clearly a loss.
That was an extreme example, but the same general rule applies:
when you have a huge hand with a bad wait, damaten is usually better.
This is especially true for flush hands, because opponents are already more likely to read them from your discards.
For hands worth mangan or less, riichi almost always raises the score.
But once you go above mangan, there are cases where adding one more han does not change the actual payout.
So from the viewpoint of final hand value, the branching line between riichi and damaten is mangan.
This is a gray zone,
and the current mainstream view is:
if the wait is good and it is still early, riichi is favored.
Example 3
Dora
Even with a hand like Example 3, which is already 7700 in damaten,
you should still riichi aggressively if the wait is good enough.
Example 4
Dora
With a hand like Example 4, where the high end is 7700 and the low end is 2000,
riichi is correct unless there is some unusual reason not to.
It does not matter whether the high tile is an outer-suji tile (1, 2, 8, 9) or an inner-suji tile (3, 4, 5, 6, 7).
Even the low-end result is still acceptable.
Example 5
Dora
With a hand like Example 5, already worth 8000 and waiting on a bad shape,
damaten is generally better.
Let us compress the above into a basic rule:
Theory
If haneman or more is already guaranteed, always take damaten.
If mangan is already guaranteed, damaten is the basic choice.
If it is an early good-shape tenpai, riichi can still be better.
For hands worth less than mangan, you should normally riichi in order to raise the value.
In that sense, not riichi'ing is the exceptional case.
From the next page on, we will continue looking at those exceptions.
Original Japanese page: http://beginners.biz/reach/reach02.html