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Shogi

Usage

import pgx

env = pgx.make("shogi")

or you can directly load Shogi class

from pgx.shogi import Shogi

env = Shogi()

Description

TBA

Specs

Name Value
Version v1
Number of players 2
Number of actions 2187
Observation shape (9, 9, 119)
Observation type bool
Rewards {-1, 0, 1}

Observation

We follow the observation design of dlshogi, an open-source shogi AI. Ther original dlshogi implementations are here. Pgx implementation has [9, 9, 119] shape and [:, :, x] denotes:

x Description
0:14 Where my piece x exists
14:28 Where my pieces x are attacking
28:31 Where the number of my attacking pieces are >= 1,2,3 respectively
31:45 Where opponent's piece x exists
45:59 Where opponent's pieces x are attacking
59:62 Where the number of opponent's attacking pieces are >= 1,2,3 respectively

The following planes are all ones ore zeros

x Description
62:70 My hand has >= 1, ..., 8 Pawn
70:74 My hand has >= 1, 2, 3, 4 Lance
74:78 My hand has >= 1, 2, 3, 4 Knight
78:82 My hand has >= 1, 2, 3, 4 Silver
82:86 My hand has >= 1, 2, 3, 4 Gold
86:88 My hand has >= 1, 2 Bishop
88:90 My hand has >= 1, 2 Rook
90:98 Oppnent's hand has >= 1, ..., 8 Pawn
98:102 Oppnent's hand has >= 1, 2, 3, 4 Lance
102:106 Oppnent's hand has >= 1, 2, 3, 4 Knight
106:110 Oppnent's hand has >= 1, 2, 3, 4 Silver
110:114 Oppnent's hand has >= 1, 2, 3, 4 Gold
114:116 Oppnent's hand has >= 1, 2 Bishop
116:118 Oppnent's hand has >= 1, 2 Rook
118 Ones if checked

Note that piece ids are

Piece Id
歩　 PAWN 0
香　 LANCE 1
桂　 KNIGHT 2
銀　 SILVER 3
角　 BISHOP 4
飛　 ROOK 5
金　 GOLD 6
玉　 KING 7
と　 PRO_PAWN 8
成香 PRO_LANCE 9
成桂 PRO_KNIGHT 10
成銀 PRO_SILVER 11
馬　 HORSE 12
龍　 DRAGON 13

Action

The design of action also follows that of dlshogi. There are 2187 = 81 x 27 distinct actions. The action can be decomposed into

  • direction from which the piece moves and
  • destination to which the piece moves

by direction, destination = action // 81, action % 81. The direction is encoded by

id direction
0 Up
1 Up left
2 Up right
3 Left
4 Right
5 Down
6 Down left
7 Down right
8 Up2 left
9 Up2 right
10 Promote + Up
11 Promote + Up left
12 Promote + Up right
13 Promote + Left
14 Promote + Right
15 Promote + Down
16 Promote + Down left
17 Promote + Down right
18 Promote + Up2 left
19 Promote + Up2 right
20 Drop Pawn
21 Drop Lance
22 Drop Knight
23 Drop Silver
24 Drop Bishop
25 Drop Rook
26 Drop Gold

Rewards

Non-zero rewards are given only at the terminal states. The reward at terminal state is described in this table:

Reward
Win +1
Lose -1
Draw 0

Termination

Termination occurs when

  1. either player checkmates the opponent, or
  2. 512 steps are elapsed (from AlphaZero [Silver+18])

Fourfold repetition is not implemented in v0.

Version History

  • v1 : Bug fix in current player by @KazukiOta in #1298 (v2.6.0)
  • v0 : Initial release (v1.0.0)