GBR code

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Leonid Kubbel
First Prize, Shakhmaty, 1925
a b c d e f g h
8
Chessboard480.svg
g8 black knight
c6 black pawn
h6 white pawn
a3 black rook
c3 black pawn
g3 white king
a2 white bishop
e1 white bishop
g1 black king
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
White to play and draw
GBR code of this study: =0323.12g3g1

The GBR code (or Guy–Blandford–Roycroft code) is a system of representing the position of chess pieces on a chessboard. Publications such as EG use it to classify endgame types and to index endgame studies.

The code is named after Richard Guy, Hugh Blandford and John Roycroft. The first two devised the original system (the Guy–Blandford code) using different figures to represent the number of pieces. Roycroft suggested to count one for a white piece and three for a black piece in order to make the code easier to memorise.


Definition[edit]

In the GBR code, every chess position is represented by six digits, in the following format:

abcd.ef

For the first four digits, each white piece counts as 1, and each black piece counts as 3. Thus, for example, if White has two knights and Black has one knight, numeral d = 1 + 1 + 3 = 5. If that is all the material other than the kings, the position is classified 0005. Values 0 through 8 represent all normal permutations of force; 9 is used if either side has promoted material.

The last two digits of the code represent the number of white and black pawns, respectively.

Usage[edit]

GBR code can be used to refer to a general class of material. For example, the endgame of two knights against pawn (as famously analysed by A.A. Troitzky, leading to his discovery of the Troitzky line), is GBR class 0002.01.

When indexing or referring to specific positions, rather than generalised material imbalances, the code may be extended in various ways. Two common ones are to prefix "+" to indicate the stipulation "White to play and win" or "=" for "White to play and draw"; and to suffix the position of the white and black kings. With these additions, the position to the right, a draw study by Leonid Kubbel (First Prize, Shakhmaty, 1925), is classified as =0323.12g3g1. (The solution is: 1.Bf2+ Kh1 2.h7 c2+ 3.Be3 Rxe3+ 4.Kf2 Rh3 5.Bd5+ cxd5 6.hxg8=Q Rh2+ 7.Kf3 c1=Q 8.Qg2+ Rxg2.) The positions of other pieces can also be added; this produces a notation that provides the same information as Forsyth–Edwards Notation.

Examples of GBR code[edit]

White material Black material GBR class
KQ K 1000
KR K 0100
KB K 0010
KN K 0001
KNN K 0002
K KN 0003
KN KN 0004
KNN KN 0005
K KNN 0006
KN KNN 0007
KNN KNN 0008
KNNN KNN 0009
KPPP KPP 0000.32
KNN KP 0002.01
KBB KN 0023
KQ KR 1300
KQP KQ 4000.10
KRP KR 0400.10
KRRP KRR 0800.10
KBBP KNN 0026.10
KBBP KRNPP 0323.12

References[edit]