论文标题

随机性的惊人力量:NP = RP

The Amazing Power of Randomness: NP=RP

论文作者

Faragó, András

论文摘要

我们(声称)证明了NP = RP一个极其令人惊讶的事实。它是通过创建一个完全多项式的随机近似方案(FPRA)来实现的,以近似计算有界度图中的独立集数,并具有任何固定度结合,这意味着NP = RP。虽然我们的方法植根于众所周知的马尔可夫链蒙特卡洛(MCMC)方法,但我们克服了一个臭名昭著的问题,即通过在独立集中生成随机样本的新想法来缓慢混合。能够结果的关键工具是解决我们称为子集采样的新型采样任务的解决方案。以其基本形式,从马尔可夫链的(指数较大)状态空间(作为输入)中给出了一个固定样本,我们希望将其转换为另一个固定样本,该样品以掉入给定的子集为条件,该样本仍然是指数级的。通常,比马尔可夫链中的固定采样更难又容易。由于子集上的条件可能比原始状态空间更复杂,因此可能更难。但是,这也可能更容易,因为已经给出了一个固定样本,从某种意义上说,这已经包含了这种采样任务的“大部分硬度”,已经处于固定分布中,这很难在缓慢混合链中到达。我们表明,有可能有效地平衡双方:我们可以利用原始空间中已经有一个固定的样本,因此可以减轻将其限制在子集中的复杂性。我们证明,考虑到所考虑的采样任务是有效的近似值,然后递归应用于创建FPRA。

We (claim to) prove the extremely surprising fact that NP=RP. It is achieved by creating a Fully Polynomial-Time Randomized Approximation Scheme (FPRAS) for approximately counting the number of independent sets in bounded degree graphs, with any fixed degree bound, which is known to imply NP=RP. While our method is rooted in the well known Markov Chain Monte Carlo (MCMC) approach, we overcome the notorious problem of slow mixing by a new idea for generating a random sample from among the independent sets. A key tool that enables the result is a solution to a novel sampling task that we call Subset Sampling. In its basic form, a stationary sample is given from the (exponentially large) state space of a Markov chain, as input, and we want to transform it into another stationary sample that is conditioned on falling into a given subset, which is still exponentially large. In general, Subset Sampling can be both harder and easier than stationary sampling from a Markov chain. It can be harder, due to the conditioning on a subset, which may have more complex structure than the original state space. But it may also be easier, since a stationary sample is already given, which, in a sense, already encompasses "most of the hardness" of such sampling tasks, being already in the stationary distribution, which is hard to reach in a slowly mixing chain. We show that it is possible to efficiently balance the two sides: we can capitalize on already having a stationary sample from the original space, so that the complexity of confining it to a subset is mitigated. We prove that an efficient approximation is possible for the considered sampling task, and then it is applied recursively to create the FPRAS.

扫码加入交流群

加入微信交流群

微信交流群二维码

扫码加入学术交流群,获取更多资源