Shogi

darklight

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	v0
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

• v0 : Initial release (v1.0.0)