Examples of $X$ halts IFF $Y$ does not halt?

40 Views Asked by At

Let $X,Y$ be algorithms that accept an ordered set of positive integers as input.

What are examples of $X$ halts if and only if $Y$ does not halt ?

Im aware that the general halting problem is undecidable.

1

There are 1 best solutions below

2
On

Take any problem that is known to be decidable, i.e. a statement $S(s)$ depending on the input $s$ such that it is known that for every $s$, either $S(s)$ or $\neg S(s)$ is provable (in a given consistent formal system). Let $X$ search all finite sequences of statements of the system for proofs of $S(s)$, halting if it finds one, and similarly let $Y$ search for proofs of $\neg S(s)$, halting if it finds one.