The concept is not far-fetched.
It's the staple of science fiction. An alternate time line where something changed history.
It is in reality too.
Communism vs the West.
Germany, East and West. They never fought, but the West won and re-unified Germany.
Vietnam. The North won and unified the country under Communism.
South Korea. They fought. Nobody won. And it is now split 50-50.
We can reverse engineer history.
Hi everyone, this is my first post on this forum, so please be a bit patient with me.
To be honest, I found this thread slightly infuriating, which caused me to create an account to comment
I had the same question yesterday and after some googling around, I found the answer. It's called 'Retrograde analyses' (which is quite a fitting name for... analyzing games while stepping backwards).
It even has a wikipedia article: https://en.wikipedia.org/wiki/Retrograde_analysis
...and a Chess programming wiki article, too: https://www.chessprogramming.org/Retrograde_Analysis
tl;dr: People are considering the problem since early 19th c., and there seem to have been some recent advances.
The threads original question could be re-stated as: "Is there is any engine that implements the un-move".
"The un-move generation is similar to move generation, with the difference that it is illegal to start in check, but legal to un-move into check, and illegal to capture, but legal to un-capture by leaving an opponent piece behind."
Also, in snoozymans quiz, answer f (10e50) is correct, not g (10^100). I'll try to explain it visually:
0% ..............................1%............................................................................................................. 100%
------------------------------------------------------------------------------------->
0 1 2 ... 10^50... 10^98........................................................................................................ 10^100
If (10^98) is only 1% of (10^100), and all the other options are smaller than (10^98), then all other options have to fall "between zero and one percent" on the number line, which leaves a 99% large gap to 10^100. So the answer has to be 10^50.
Please correct me if I'm wrong. Also, sorry for ... disturbing this peacefully sleeping thread, I guess.
@Fins5090
What a funny question.
Funnier that it exists in real life.