% Francois Labelle & computer, January 24, 2004
% All 12 at home PG-4.0 with exactly 2 solutions.
% They are all SPGs.

% Comment by Joost de Heer (January 28, 2004):
%
% Only one acceptable double-solution proofgame in 8 halfmoves:
% 
% rnbqkbnr/pp1ppppp/8/8/8/8/PPP1PPPP/RN1QKBNR
% SPG 4.0 (2 solutions)
%
% 1. d4 Nc6 2. Bf4 Nd4 3. Bc7 Nc6 4. Bb8 Nb8
% 1. d4 c5 2. Bh6 cd4 3. Qd4 Nh6 4. Qd1 Ng8
%
% These two solutions are distinct enough to be acceptable. A pity is
% the repeated first move.

% Comment:
%
% This "acceptable double-solution proofgame" was discovered before
% by Cornel Pacurar (see http://anselan.com/CHEB.html).


(Forsyth-Edwards Notation, followed by the same list in ascii diagrams)

SPG-4.0:

rnbqkbn1/ppp2ppp/8/8/8/8/PPPPPPPP/R1BQKBNR
rnb1kbnr/ppppp1pp/8/8/8/8/PPPPPPPP/R1BQKBNR
rnbqkbnr/pppp1ppp/8/8/8/8/PPP1PPPP/R1BQKBNR
rnbqkbnr/pppp1ppp/8/8/8/8/1PP1PPPP/RNBQKBNR
1nbqkbnr/ppp2ppp/8/8/8/8/PPPPPPPP/RNBQKB1R
rn1qkbnr/ppp1pppp/8/8/8/8/PPPP1PPP/RNBQKBNR
r1bqkbnr/ppp1pppp/8/8/8/8/PPPP1PPP/RNBQKBNR
rnbqkbnr/ppp1ppp1/8/8/8/8/PPPP1PPP/RNBQKBNR
rnbqkbnr/1pp1pppp/8/8/8/8/PPPP1PPP/RNBQKBNR
rnbqkbnr/pppp1ppp/8/8/8/8/PPP1PPP1/RNBQKBNR
rnbqkbnr/pppp1ppp/8/8/8/8/PPP1PPPP/RN1QKBNR
rnbqkbnr/pp1ppppp/8/8/8/8/PPP1PPPP/RN1QKBNR

 _________________ _________________ _________________ _________________ 
|                 |                 |                 |                 |
| r n b q k b n . | r n b . k b n r | r n b q k b n r | r n b q k b n r |
| p p p . . p p p | p p p p p . p p | p p p p . p p p | p p p p . p p p |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
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| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| P P P P P P P P | P P P P P P P P | P P P . P P P P | . P P . P P P P |
| R . B Q K B N R | R . B Q K B N R | R . B Q K B N R | R N B Q K B N R |
|_________________|_________________|_________________|_________________|
|                 |                 |                 |                 |
| . n b q k b n r | r n . q k b n r | r . b q k b n r | r n b q k b n r |
| p p p . . p p p | p p p . p p p p | p p p . p p p p | p p p . p p p . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| P P P P P P P P | P P P P . P P P | P P P P . P P P | P P P P . P P P |
| R N B Q K B . R | R N B Q K B N R | R N B Q K B N R | R N B Q K B N R |
|_________________|_________________|_________________|_________________|
|                 |                 |                 |                 |
| r n b q k b n r | r n b q k b n r | r n b q k b n r | r n b q k b n r |
| . p p . p p p p | p p p p . p p p | p p p p . p p p | p p . p p p p p |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| . . . . . . . . | . . . . . . . . | . . . . . . . . | . . . . . . . . |
| P P P P . P P P | P P P . P P P . | P P P . P P P P | P P P . P P P P |
| R N B Q K B N R | R N B Q K B N R | R N . Q K B N R | R N . Q K B N R |
|_________________|_________________|_________________|_________________|