What is duplicate mahjong?
Duplicate Mahjong (DM) is a mahjong format in which the result of each deal is compared with the results of the same deal played at other tables regardless of the mahjong rules themselves.
There are two major types of duplicate tournaments:
- In a team tournament, a team plays the same deal on all four winds, four individual results are then summed up and converted into the IMP* according to the scale.
- In an individual tournament, one hand can be played any number of times, the player in each hand receives a deviation of his result from the average in this hand on the same wind, converted into the IMP* according to the scale.
* IMP is an abbreviation from International Match Point, such a unit is used in duplicate bridge, a game much influenced on DM development.
MCR Duplicate Rules
- Each player has a “personal” wall, whenever a player cannot take a tile from his/her wall the play stops, it is a draw.
- All bonus tiles are eliminated since their presence may lead to “uneven” opportunities to draw tiles by the players.
Rule 1. Self-drawn win
- When winning from the wall with the hand value “HV” the winner gains (HV+24) pts., and others lose (HV/3-8) pts. rounded to the closest highest integer.
- The rule eliminates the “random” factor of drawing winning tile.
Examples: HV=9 --> +33 / -11pts. ; HV=10 --> +34 / -12 pts.
Rule 2. Multiple “Hu”
- When declaring “Hu” by several players on discard, all players without a false “Hu” gain points.
- The rule eliminates the “random” factor of the winners’ relative position at the table.
Example: player A discards a tile for player B’s Hu_1=20 pts. and player C’s Hu_2=10 pts. Each winner receives a “standard” score of “Hu+24 pts.” but also they have to pay to the other winner. So, A=-(20+8)-(10+8)=-46 pts., B= (20+24)-8=36 pts., C=(10+24)-8=26 pts., D=-8-8=-16 pts.
Rules 3A/3B. Kong
- A replacement tile is taken from the right end of the wall.
- It is forbidden to declare kong when there are no tiles in the player’s wall.
Definition of the last tile of the wall (LTW):
- “If it is the turn of a player but there is no tile in the wall of the next player, the last tile of the wall point is reached”.
Example: South has no tiles in his wall. If East receives the right to make a turn then a point of LTW is reached. Please, note that besides an obvious case of starting turn by East after North’s unclaimed discarded tile East can also gain turn after his Chow/Pung/Kong declaration.
Rule 4. Declarations on the last tile of the wall
- After the point of reaching LTW, no declarations can be made except “Hu”.
Example: after drawing tile after LTW point a player can declare neither Concealed Kong nor Promoted Kong even if there is a possible replacement tile in his wall.
Rules 5A/5B. The last tile of the wall
- Fan “Last Tile Draw” is added on “Hu” of a player who drew the tile from the wall after the point of reaching LTW.
- Fan “Last Tile Claim” is added to all players with “Hu” on the discarded tile after the point of reaching LTW.
Game points to IMP conversion table
One can see what duplicate mahjong is in the tutorial Duplicate Mahjong. Please, read about it in a Duplicate Mahjong Bulletin.