Derandomized Parallel Repetition via Structured PCPs

Irit Dinur, Or Meir

Research output: Contribution to journalArticlepeer-review


A PCP is a proof system for NP in which the proof can be checked by a probabilistic verifier. The verifier is only allowed to read a very small portion of the proof and in return is allowed to err with some bounded probability. The probability that the verifier accepts a proof of a false claim is called the soundness error and is an important parameter of a PCP system that one seeks to minimize. Constructing PCPs with subconstant soundness error and, at the same time, a minimal number of queries into the proof (namely two) is especially important due to applications for inapproximability. In this work, we construct such PCP verifiers, i.e., PCPs that make only two queries and have subconstant soundness error. Our construction can be viewed as a combinatorial alternative to the "manifold vs. point" construction, which is the basis for all constructions in the literature for this parameter range. The "manifold vs. point" PCP is based on a low-degree test, while our construction is based on a direct product test. We also extend our construction to yield a decodable PCP (dPCP) with the same parameters. By plugging in this dPCP into the scheme of Dinur and Harsha (FOCS 2009), one gets an alternative construction of the result of Moshkovitz and Raz (FOCS 2008), namely a construction of two-query PCPs with small soundness error and small alphabet size. Our construction of a PCP is based on extending the derandomized direct product test of Impagliazzo, Kabanets, and Wigderson (STOC 09) to a derandomized parallel repetition theorem. More accurately, our PCP construction is obtained in two steps. We first prove a derandomized parallel repetition theorem for specially structured PCPs. Then, we show that any PCP can be transformed into one that has the required structure, by embedding it on a de-Bruijn graph.

Original languageEnglish
Pages (from-to)207-327
Number of pages121
JournalComputational Complexity
Issue number2
StatePublished - Jun 2011
Externally publishedYes

Bibliographical note

Funding Information:
Irit Dinur is supported in part by the Israel Science Foundation and by the Binational Science Foundation and by an ERC grant. Or Meir is supported in part by the Israel Science Foundation (grant No. 1041/08) and by the Adams Fellowship Program of the Israel Academy of Sciences and Humanities. An extended abstract of this paper has appeared as Dinur & Meir (2010).


  • PCP
  • de-Bruijn
  • derandomized parallel repetition
  • direct product
  • direct product test
  • low error

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Mathematics
  • Computational Theory and Mathematics
  • Computational Mathematics


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  • Derandomized parallel repetition of structured PCPs

    Dinur, I. & Meir, O., 2010, Proceedings - 25th Annual IEEE Conference on Computational Complexity, CCC 2010. p. 16-27 12 p. 5497901. (Proceedings of the Annual IEEE Conference on Computational Complexity).

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

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