The Busy Beaver Problem
A NEW MILLENNIUM ATTACK
Mirror Machines
The two machines pictured below are not identical, and they are not isomorphic. Rather, for each move transition in one machine, the other specifies the same transition, just with the oppositve movement. All write transitions are identical. As a result, when one machine moves right, the other moves left and vice versa. It is easy to see that these two machines will be equally as productive but will behave in a mirrored fashion to one another. There is no need, therefore, to consider both machines.
Mirror1
Mirror2
Solution: Mirror Machines
The solution to eliminating mirror machines is actually quite simple. By simply forcing the first move to always be to the right, it is impossible to generate any mirror machines. In addition, the completeness of the search remains in tact because for any machine that would have been produced if its first move was a left, its mirror machine is guaranteed to be enumerated at some point by the tree. Combined with the Empty tape and nonproductive transition filters, this leaves us with the following initial search tree:
Search tree
Optimization Filters
Project Components
Current Champions
n B(n) b(n) O(n) o(n)
1 1T 1T 1T 1T
2 2T 3T 2T 3T
3 3? 13R 3O 13R
4 5? 31R 8O 37R
5 11? 57R 15O 111O
6 25M 255M 239R 41606R
7 196M 13682M

8 672M 198339M


n P(n) p(n) R(n) r(n)
1 1T 2T 1T 2T
2 2T 4T 2T 4T
3 4R 14R 4R 14R
4 7R 32R 8R 38R
5 16R 112R 16R 112R
6 163R 27174R 240R 41607R

RSet by present RPI effort
MSet by Machado and Pereira
OSet by Oberschelp, et al.
TTrivial records
?Unknown origin

Also note: A solid yellow background indicates records have been explicitly confirmed by the present effort. A faded yellow indicates relative confidence but not yet an explicit proof.
Busy Beaver Research Team
Bram van Heuveln
Selmer Bringsjord
Boleslaw Szymanski
Carlos Varela
Kyle Ross
Owen Kellett
Shailesh Kelkar