Article 1 – Purpose and Applicability

1.1 The World Open Shogi Championship applies the MacMahon pairing system to ensure fair competition between players of comparable playing strength.

1.2 These regulations govern the initial allocation of players to MacMahon groups, the minimum size of such groups, and exceptional promotions related to the European Shogi Championship (ESC).

1.3 These rules apply to all participants of the World Open Shogi Championship.

Article 2 – Rank and Elo Reference

2.1 Each player is assigned an initial reference Elo rating based on their officially recognized Shogi rank.

2.2 The following Rank–Elo Reference Table is used for MacMahon group allocation:

Article 3 – Top MacMahon Group

3.1 Definition

3.1.1 The Top MacMahon Group consists of the Top 16 European players as determined by the final standings of the European Shogi Championship (ESC).

3.1.2 The 16th-ranked ESC player is determined exclusively by the actual ESC participants and their final ranking, and not by any fixed rating threshold.

3.1.3 The Elo rating of the 16th-ranked ESC player serves as a reference value for determining the lower boundary of the Top MacMahon Group.

3.1.4 In the reference scenario used for this regulation, the 16th-ranked ESC player has an Elo rating of 1821, corresponding to 2 Dan according to the Rank–Elo Reference Table.

3.1.5 Consequently, the Top MacMahon Group starts at 2 Dan (Elo ≥ 1800) for initial group allocation, provided the minimum group size requirement defined in Article 4 is satisfied.

Article 4 – Minimum Group Size

4.1 Each MacMahon group must consist of at least ten (10) players.

4.2 If the number of players at a given rank level is insufficient to reach the minimum group size, the next lower adjacent rank(s) shall be included until the minimum size is met.

4.3 Once a MacMahon group is formed, no player may belong to more than one group at the initial allocation stage.

Article 5 – Allocation of Lower MacMahon Groups

5.1 After the Top MacMahon Group has been established, all remaining players shall be allocated to additional MacMahon groups.

5.2 These groups are formed in descending order of rank, applying the minimum group size rule set out in Article 4.

5.3 Adjacent rank levels shall be merged where necessary to ensure compliance with the minimum group size requirement.

Article 6 – Promotion from the European Shogi Championship

6.1 Any player participating in the European Shogi Championship (ESC) who advances to Round 2 of the ESC shall be automatically promoted to the Top MacMahon Group of the World Open Shogi Championship.

6.2 This promotion takes effect after the completion of Round 1 of the World Open Shogi Championship.

6.3 A promoted player shall receive the initial MacMahon score of the Top MacMahon Group, irrespective of their original group allocation.

Article 7 – Calculation Examples

7.1 Example: Top MacMahon Group Formation

Since all players are ranked 2 Dan or higher, and the minimum group size is exceeded, all are assigned to the Top MacMahon Group.

7.2 Example: Second MacMahon Group Formation

As 1 Dan alone does not reach the minimum group size, 1 Kyu is included.

➡️ MacMahon Group: 1 Dan – 1 Kyu

7.3 Example: Lower MacMahon Group Formation

➡️ MacMahon Group: 2 Kyu – 4 Kyu

Article 8 – Exceptional Cases

8.1 The Tournament Director may make minor adjustments in exceptional circumstances, such as unexpected registration numbers or rating inconsistencies.

8.2 Any adjustment must preserve:

• the minimum group size, and
• the principle of competitive balance.

Article 9 – Final Provisions

9.1 These regulations enter into force upon publication.

9.2 By registering for the World Open Shogi Championship, all players agree to be bound by these regulations.

9.3 The decisions of the Tournament Director are final.