Class Description

coRP: Complement of RP

Defined in [Gil77]. (This paper does not actually discuss coRP, other than implicitly mentioning that ZPP = RP ∩ co-RP. Is there a better reference?)

Contains the problem of testing whether an integer is prime [SS77].

Linked From 3 Classes

BC=P: Bounded-Error C=P

The class of decision problems solvable by an NP machine such that

  1. If the answer is 'yes' then exactly 1/2 of the computation paths accept.
  2. If the answer is 'no' then either at most 1/4 or at least 3/4 of the computation paths accept.

(Here all computation paths have the same length.)

Defined in [Wat15], where it was shown that BC=P admits efficient amplification and is closed under union, intersection, disjunction, and conjunction, and that coRP ⊆ BC=P ⊆ BPP.

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RP: Randomized Polynomial-Time

The class of decision problems solvable by an NP machine such that

  1. If the answer is 'yes,' at least 1/2 of computation paths accept.
  2. If the answer is 'no,' all computation paths reject.

Defined in [Gil77] (implicitly: the class VPP that is defined is equivalent to RP by running the recognizer as many times as necessary to reach probability 1/2).

Contains the problem of testing whether an integer is prime [AH87], although this problem was subsequently shown to be in P [AKS02].

For other problems in RP, see the standard text on randomized algorithms, [MR95].

Has the same p-measure as ZPP. Moreover, this measure is either zero or one. If the measure is non-zero, then ZPP = BPP = EXP [IM03].

See also: coRP, ZPP, BPP.

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ZPP: Zero-Error Probabilistic Polynomial-Time

Defined as RP ∩ coRP.

Defined as the class of problems solvable by randomized algorithms that always return the correct answer, and whose expected running time (on any input) is polynomial, in [Gil77]. (Proposition 5.5(iii) in this paper shows that the two definitions above are equivalent.)

Contains the problem of testing whether an integer is prime [SS77] [AH87].

In contrast to BPP and RP, it is not known whether showing ZPP = P requires proving superpolynomial circuit lower bounds [KI02].

There exists an oracle relative to which ZPP = EXP [Hel84a], [Hel84b], [Kur85], [Hel86].

Has the same p-measure as RP. Moreover, this measure is either zero or one. If the measure is non-zero, then ZPP = BPP = EXP [IM03].

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