5-state busy beaver winner: Difference between revisions

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Add Michel version of formula (which I think is much simpler).
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The 5-state busy beaver champion (and winner!) is: [https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA&status=halt https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA]. It was found by Heiner Marxen and Jürgen Buntrock in 1989<ref>H. Marxen and J. Buntrock. Attacking the Busy Beaver 5. Bulletin of the EATCS, 40, pages 247-251, February 1990. https://turbotm.de/~heiner/BB/mabu90.html</ref>. The machine halts after 47,176,870 steps and with 4098 1's on the tape, showing that <math>BB(5) \ge 47,176,870</math> and <math>\Sigma(5) \ge 4098</math>.
The 5-state busy beaver champion (and winner!) is: [https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA&status=halt https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA]. It was found by Heiner Marxen and Jürgen Buntrock in 1989<ref>H. Marxen and J. Buntrock. Attacking the Busy Beaver 5. Bulletin of the EATCS, 40, pages 247-251, February 1990. https://turbotm.de/~heiner/BB/mabu90.html</ref>. The machine halts after 47,176,870 steps and with 4098 1's on the tape, showing that <math>BB(5) \ge 47,176,870</math> and <math>\Sigma(5) \ge 4098</math>.


== Behavior ==
This machine repeatedly applies the following map, starting with <math>x = 0</math><ref>Aaronson, S. (2020). The Busy Beaver Frontier. Page 10-11. https://www.scottaaronson.com/papers/bb.pdf</ref>:
This machine repeatedly applies the following map, starting with <math>x = 0</math><ref>Aaronson, S. (2020). The Busy Beaver Frontier. Page 10-11. https://www.scottaaronson.com/papers/bb.pdf</ref>:
<math display="block">\begin{align}
<math display="block">\begin{align}
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   g(x) & \to \frac{5x+22}{3} && \text{if }x \equiv 1 \pmod{3} \\
   g(x) & \to \frac{5x+22}{3} && \text{if }x \equiv 1 \pmod{3} \\
   g(x) & \to \text{HALT}    && \text{if }x \equiv 2 \pmod{3}
   g(x) & \to \text{HALT}    && \text{if }x \equiv 2 \pmod{3}
\end{align}</math>which can alternatively be written as<ref>Pascal Michel. Behavior of busy beavers.https://bbchallenge.org/~pascal.michel/beh#tm52a</ref>:
<math display="block">\begin{align}
  g(3k)  & \to 5k+6 \\
  g(3k+1) & \to 5k+9 \\
  g(3k+2) & \to \text{HALT} \\
\end{align}</math>
\end{align}</math>



Revision as of 03:03, 10 July 2024

The 5-state busy beaver champion (and winner!) is: https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA. It was found by Heiner Marxen and Jürgen Buntrock in 1989[1]. The machine halts after 47,176,870 steps and with 4098 1's on the tape, showing that BB(5)47,176,870 and Σ(5)4098.

Behavior

This machine repeatedly applies the following map, starting with x=0[2]: g(x)5x+183if x0(mod3)g(x)5x+223if x1(mod3)g(x)HALTif x2(mod3)which can alternatively be written as[3]:

g(3k)5k+6g(3k+1)5k+9g(3k+2)HALT

The full orbit from x=0 is: 06163464114196334564946158426464416736612284HALT

  1. H. Marxen and J. Buntrock. Attacking the Busy Beaver 5. Bulletin of the EATCS, 40, pages 247-251, February 1990. https://turbotm.de/~heiner/BB/mabu90.html
  2. Aaronson, S. (2020). The Busy Beaver Frontier. Page 10-11. https://www.scottaaronson.com/papers/bb.pdf
  3. Pascal Michel. Behavior of busy beavers.https://bbchallenge.org/~pascal.michel/beh#tm52a