แนวคิดหลัก
The authors construct efficient interactive proof systems that enable a verifier to check the results of an untrusted learner for various classes of Boolean functions, including heavy Fourier characters, AC0[2] circuits, and k-juntas, while using significantly fewer samples than the learner.
บทคัดย่อ
The paper presents several results on constructing efficient interactive proof systems for verifying the results of agnostic learning algorithms over the uniform distribution:
- Learning Heavy Fourier Characters:
- The authors construct an interactive protocol where the verifier uses only poly(t/ε) random examples to learn the t heaviest Fourier characters of a given Boolean function up to an error ε. This improves upon the previous protocol of [GRSY21] whose sample complexity depended on the number of variables n.
- The key ideas are a novel algorithm for approximately computing the highest t Fourier coefficients, and a framework for reducing the number of queries to samples.
- Learning AC0[2] Circuits:
- The authors show that for any function f such that the distance of f from AC0[2] circuits is non-negligible, the class AC0[2] is (polylog(n), 1/10)-PAC-verifiable over the uniform distribution, where the verifier uses at most quasi-polynomially many random examples.
- This builds on the agnostic learner for AC0[2] from [CIKK17] and a careful analysis of the query patterns in their algorithm.
- Learning Juntas:
- The authors construct a PAC-verification protocol for the class of k-juntas, where the verifier uses only 2^k · poly(k/ε) random examples, while the honest prover uses k^2^k/ε^2 · log(n) examples.
- This is obtained by a general transformation from tolerant testers to PAC-verifiers, combined with the query-to-sample reduction framework.
- Unbounded Provers:
- The authors show that if the honest prover is allowed to be computationally unbounded, then any class of Boolean functions can be distribution-free, proper, (ε, 1/10)-PAC-verifiable using only O(1/ε) random examples.
- This is achieved by viewing agnostic learning as an Empirical Risk Minimization task and delegating it to an unbounded prover.
Overall, the paper demonstrates the power of interactive proofs in verifying the results of agnostic learning algorithms, achieving quantitative and qualitative improvements over standalone learners.