[Retros] Retractor v2.2 with cage verfication released
hwatheod at cs.stanford.edu
Sat May 20 18:03:35 EDT 2023
In a previous message  I discussed a cage verification algorithm for
improving the solving capabilities of Retractor. This has now been
implemented in Retractor v2.2. As usual, this latest version is available
You may need to do a hard refresh (Shift-refresh) if your browser has the
previous version cached. Make sure it says "Welcome to Retractor 2.2".
To learn more about the cage feature, with some examples, click the
"Cages" link towards the bottom of the Retractor page above.
Cage verification is a form of human-assisted solving, but still fully
verified by the computer. When humans supply appropriate cages, Retractor
v2.2 is able to verify them and then solve an additional 23 type A, 24
type B, 7 type C, and 16 type D last move problems at , compared with
As a quick example, consider the first problem 8/011 at ,
8/8/8/8/8/1P6/1PkPP3/KR1b4 (last move?). Initially, Retractor is unable to
rule out the incorrect uncapture a2xb3. However, after the incorrect
uncapture a2xb3, the lower left corner (a1-e2 rectangle) forms a cage
because that configuration can never be unlocked no matter what we do
from here. In Retractor v2.2, the user can input the position in the a1-e2
rectangle as a cage, and Retractor can verify the cage. After that,
Retractor can rule out the illegal a2xb3 and find the unique solution to
the original problem.
Any comments or questions are welcome!
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