Holdouts lists: Difference between revisions
(Removed the section (and tables) that were attempting to document how someone could attain some of the holdout lists. This is being moved to the wiki page for the specific BB domain.) |
(Pointed out the "Number of holdouts" table is not independently verified in cases where the number of holdouts is not zero.) |
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Holdout lists are often shared by contributors. There is a [[#Downloadable Holdout Lists|Downloadable Holdout Lists]] table where people have added lists with no restriction or independent verification. For some of the entries there is a reference to a spreadsheet that documents what was run to achieve the result. For others, there is additional documentation on the specific BB pages. | Holdout lists are often shared by contributors. There is a [[#Downloadable Holdout Lists|Downloadable Holdout Lists]] table where people have added lists with no restriction or independent verification. For some of the entries there is a reference to a spreadsheet that documents what was run to achieve the result. For others, there is additional documentation on the specific BB pages. | ||
The table with the "Number of holdouts" is based on the holdout lists listed in the table below it. Thus, some of these numbers have not been independently verified so they should be treated as such. All the zero entries, no holdouts, have been verified. | |||
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Revision as of 07:00, 28 February 2025
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. There is a Downloadable Holdout Lists table where people have added lists with no restriction or independent verification. For some of the entries there is a reference to a spreadsheet that documents what was run to achieve the result. For others, there is additional documentation on the specific BB pages.
The table with the "Number of holdouts" is based on the holdout lists listed in the table below it. Thus, some of these numbers have not been independently verified so they should be treated as such. All the zero entries, no holdouts, have been verified.
| 2-state | 3-state | 4-state | 5-state | 6-state | |
|---|---|---|---|---|---|
| 2-symbol | 0 | 0 | 0 | 0 | 4408 |
| 3-symbol | 0 | 6 | 460,916,384 | ||
| 4-symbol | 0 | 434,787,751 | |||
| 5-symbol | 273 | ||||
| 6-symbol | 22,302,296 |
Downloadable Holdout Lists
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.