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MatPlus.Net  Forum General Longest "forcing" retro |
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| | | (1) Posted by Hauke Reddmann [Sunday, May 7, 2023 09:32] | Longest "forcing" retro
The answer to the following three questions should be solvable with
a simple lookup (I don't know the actual values):
- Position given, longest number of moves leading to it
- Longest direct "Rückzüger" from position given (without fairy):
White takes back n moves (forcing Black to answer), then #1
- Longest help "Rückzüger" from position given, likewise
But assume we go only for longest unique forcing Black-only retro.
Position to be constructed. White takes back a move which forces
Black to an unique retro-reply, repeat ad nauseam. 3x repetition
of position stops. I guess with double checks, still Black can
be kicked around at least hundred of moves. Any attempt?
Random example:
 (= 16+2 )
Last Black move Kb8-a8. White takes back Kb6-a6, forcing Black
to take back Kc8-b8 and so until arrival at the other corner.
| | | (2) Posted by James Malcom [Monday, May 8, 2023 08:11] |
To be clear, the example position maxes out at 16 moves, wherein Kb6&Kb8 is reached for the third time.
EDIT: Disregard what was here, spent way to many hours working with a non-working I idea I realized too late.
| | | (3) Posted by James Malcom [Monday, May 8, 2023 09:08] |
What exactly are the restrictions, Hauke? I assume each of your three questions pertains to a retractor problem, but it isn't quite clear
For the main challenge, need White's be unique? If not, we can have this be the end position, meaning an incalculable number of positions can be repeated twice, and technically Black's last move in the two-move loop is unique and the only possible last move each time.
 (= 15+9 )
Many many questions to be answered first.
| | | (4) Posted by Hauke Reddmann [Tuesday, May 9, 2023 22:36] |
Nr. 1 is the n record of "Last n moves?"
Nr. 2 is the longest orthodox retractor. I dimly remember
someone got a titanic number by perusing the 50 move rule.
In Nr. 3, indeed there are no further restrictions, White
may take back anything, not uniquely, as long as Blacks
take back is forced, just for the sake of the record.
I guess the number is even more titanic...
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