No.1736
Shankar Ram
(India)
Original Fairy problems
JF-R2023-24:
01.01.2023 - 31.12.2024
☝ Definitions
No. 1736 Shankar Ram
India
original - 18.02.2023
White Kf1 Rh3
Black Kh1 Bh2 Ph7
DPG 3.5 2+3
Defensive Proof Game in 3.5 moves
Type A->B, where position A=diagram, position B =A with Ph7 on h4
Defensive Proof Game in 3.5 moves
Type A->B, where position A=diagram, position B =A with Ph7 on h4
Solution: (click to show/hide)
Improved version 1736.1 25.02.2025
a) DPG 3.5 (Defensive Proof Game A->B)
b) Self PG 3.0 (Self Proof Game A->B: White forces Black to reach the stipulated position)
c) move WRh3-h5 PG 2.0 (Normal [help] PG A->B)
a) 1.Rh5! h6 2.Rh3 h5 3.Kf2 h4 4.Kf1
b) 1.Rh5! h6 2.Rh4 h5 3.Rh3 h4
c) 1.Rh4 h5 2.Rh4 h3
So is the number of moves the only difference between a defensive proof game and a self proof game? If a defensive proof game has a whole number of moves then is a self proof game just another name for the same thing?
There might be situations where there is more than a half-move gap between a DPG and a Self PG, even if leading to the same final position, though, of course, a DPG will always have an odd number of plies (half-moves) and a Self PG will always have an even number of plies. Have to compose a “proof of concept” problem to prove that!
Here’s one:
Also, in line with direct mates and selfmates, a DPG always ends with a White move, and a Self PG always ends with a Black move.