提出可验证概率预测一致性的高效协议,确保AI不自相矛盾。
How to Verify Consistency of Probabilistic Claims
- 设计交互式PCP协议,用少量查询验证概率模型一致性
- 证明在多项式时间内可检测模型输出是否近似自洽
- 为训练模型自我证明一致性提供理论基础,适合安全关键场景
当概率预测模型回答大量条件概率问题时,其答案是否自洽?能否在多项式时间内验证?该问题对人工智能安全至关重要,因安全依赖于对潜在不良后果的概率诚实预测。本文构造一种交互式PCP协议:给定由概率电路P和置信度电路Q定义的模型,二者隐含指数级多的概率主张。验证者仅需在少数点评估(P,Q),并读取一个编码了声称一致的概率分布的证明预言机,在与单一不可信证明者交互中完成验证。为此,需保证存在稀疏的、与模型预测一致的见证分布。研究首先考虑显式概率主张(如m个形如Pr[Y=1|X=x]=p的命题,涉及n个布尔变量)的一致性;基于Nilsson(1986)工作,将l_2近似一致性归入NP,证书长度为O(mn + log B),其中B为输入比特精度;进一步表明,小的加性完备性-可靠性间隙可消除对B的依赖。这些结果为认证概率预测自洽性提供了复杂性理论基础。本协议被视为训练模型自我证明一致性的第一步。
原文摘要 · Abstract (English)
When a probabilistic predictor answers many conditional-probability queries, are its answers self-consistent, and can this be verified in polynomial time? This problem is of interest for AI safety, where safety is derived from honesty about probabilistic predictions of unwanted outcomes potentially caused by an AI action. We construct an interactive PCP as follows. Let a predictive model be specified by a probability circuit P and a circuit Q which outputs confidence in predictions. Together, P and Q implicitly specify exponentially many probabilistic claims. We show a protocol in which a polynomial-time verifier can verify the approximate consistency of (P,Q). The verifier is given the pair of circuits (P,Q), which it evaluates at only a few points; alongside them it is given a proof oracle, an encoding of a witnessing probability distribution allegedly consistent with the predictions of (P,Q), which it reads at a few locations while interacting with a single untrusted prover. En route, we must ensure the existence of a sparse witnessing distribution consistent with the model's predictions. To do so, we first consider witness distributions for the consistency of explicit probabilistic claims, rather than claims specified by a predictor: say m claims, each of the form Pr[Y = 1 | X = x] = p, over n Boolean variables. Building on work initiated by Nilsson (Artif. Intell., 1986), we place l_2-approximate probabilistic consistency of explicit claims in NP, with certificates of length O(mn + log B) in the input bit-precision B; we further show how a small additive completeness-soundness gap removes the dependence on B. Together these results provide a complexity-theoretic foundation for certifying the self-consistency of probabilistic predictors. We view our interactive PCP as a first step toward training predictive models to prove their own consistency.
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