1 of 19

Considering Four-Tile Groups

Hand Building

2 of 19

Five Block Theory: A Brief Refresher

~97% of winning hands follow a standard structure of four sets and one pair:

40%+ of winning hands include the Riichi yaku (scoring pattern), which requires a closed hand.
If we want to reach tenpai (ready for a winning tile) as fast as possible, we want to identify five “blocks” to build into the completed hand’s elements.

3 of 19

Five Block Theory: A Brief Refresher

A “block” is a completed set (sequence or triplet), or a group of two or three tiles that can become a set.

Six blocks in hand: Trim the weakest group from the hand.
Five blocks in hand: The weakest group should be as strong as possible.

edge

(penchan)

closed

(kanchan)

2-sided

(ryanmen)

pair

(toitsu)

2-sided + pair

<

4 of 19

Five Block Theory: A Brief Refresher

Four or fewer blocks in hand: Keep floating tiles with the highest chance of developing into a block.

honors

1, 9 (terminals)

2, 8

3-7

<

In practice, pure efficiency must also be balanced with considerations of score (e.g. holding floating dora tiles) and safety (e.g. holding a safe honor when incomplete blocks are ryanmen or better)

5 of 19

Groups with Four Tiles

Completed sets consist of three tiles → each block should consist of two or three tiles at most
Groups of four related tiles are often “bulky”: either having one too many tiles for a single block, or better considered as two simple two-tile blocks.

+

6 of 19

Completed Set + Extra Tile

7 of 19

Completed Set + Extra Tile

extended sequence

(yonrenkei)

bulging sequence

(nakabukure)

paired end sequence

(aryanmen)

sequence with gap tile

triplet + adjacent tile

triplet + gap tile

8 of 19

Completed Set + Extra Tile

accepts

5 types

19 tiles

8 types

28 tiles

5 types

16 tiles

6 types

22 tiles

9 of 19

Completed Set + Extra Tile

accepts

5 types

19 tiles

6 types

20 tiles

5 types

16 tiles

5 types

16 tiles

10 of 19

Completed Set + Extra Tile

accepts

5 types

19 tiles

6 types

20 tiles

5 types

16 tiles

5 types

16 tiles

11 of 19

Example: Triplet + Floating Tile

East 1-0

North Seat

Turn 5

What do you discard from this hand?

Answer: Discard

We already have two other pairs in the hand, but no realistic option to open our hand with calls. Better for us to have the widest tile acceptance, and is just slightly better than keeping .

12 of 19

Two Incomplete Sub-Blocks

13 of 19

Compound Block + Extra Tile

14 of 19

Choosing a Compound Block

accepts

2 types

8 tiles

accepts

2 types

6 tiles

accepts

3 types

8 tiles

15 of 19

Example: Choosing a Compound Block

What do you discard from this hand?

East 1-0

West Seat

Turn 5

Answer: Discard

We have a 3-han hand that we can open to win; discarding lets us call pon on to reach 4 han while still having a pair to reach tenpai.

16 of 19

Overlapping Tile Acceptance

17 of 19

Overlapping Tile Acceptance

accepts

3 types

12 tiles

4 types

16 tiles

4 types

12 tiles

4 types

16 tiles

18 of 19

Example: Overlapping Tile Acceptance

East 1-0

East Seat

Turn 5

G. Uzaku WWYD Gold

Problem 21

What do you discard from this hand?

Answer: Discard

Drawing means we now have six blocks and can cut bamboo from two blocks to one. Discarding from either pair is fine, but is slightly more dangerous since it can be part of two different ryanmen waits.

19 of 19

Non-Interacting Sub-Blocks

<

=

completes

rather than

For completeness, there are two other ways of combining two two-tile groups, but where they do not particularly interact. For the left group, the ryanmen 34s does not interact with the 66s pair at all; trimming down to 466s would actually have a smaller tile acceptance compared to the ryanmen unless we have a second pair. For the central group, drawing 6s looks like it might fill in a 57s closed group, but it really just completes the 78s ryanmen to leave the incomplete 35s closed block. On the right, the 35s and 68s kanchan groups do not affect each others’ tile acceptances, but we could also drop 38s to leave a single 56s ryanmen block with the same overall tile acceptance. So we can keep the two kanchan if we need the two groups, but drop 38s if we develop a stronger ryanmen group elsewhere (or draw a 2s to connect to 3s – two ryanmen with overlapping ukeire is still better than two kanchan).