Holdouts lists
A holdout (or undecided machine) is a Turing machine for which it is not known whether the machine halts or not from all-0 input tape. Holdouts are the machines which deciders are unable to decide.
Holdout lists are often shared by contributors:
| BB space | Date | Shared by | Number of holdouts | File | Notes |
|---|---|---|---|---|---|
| BB(6) | August 4, 2024 | @mxdys | 5877 | File:BB6 holdouts 5877.txt | |
| BB(6) | July 6, 2024 | @mxdys | 7296 | File:BB6 holdouts 7296.txt | |
| BB(2,5) | June 15th 2024 | @dyuan01 | 273 | File:2x5_holdouts_273.txt | @Justin Blanchard's 499 holdouts minus machines solved by @mxdys |
| BB(6) | June 13th 2024 | @tjligocki | 12,091 | File:BB6 holdouts 12091.txt | Work done with @Shawn Ligocki |
| BB(3,3) | June 9th 2024 | @Justin Blanchard | 22 | File:3x3.todo.txt, File:Mugshots small.pdf | |
| BB(6) | June 7th 2024 | @mxdys | 12,325 | File:BB6 holdouts 12325.txt | Some equivalent machines are removed. |
| BB(2,5) | May 22nd 2024 | @Justin Blanchard | 499 | File:2x5.todo.txt | |
| BB(5) | 0 |
Georgi Georgiev (Skelet) posted a list of 43 holdouts for BB(5) in 2003. bbchallenge.org successfully reduced the number of holdouts for BB(5) to zero in June 2024.