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arXiv 1804.02520cs.CC
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小深度多线性电路的一个近优深度层次定理

A Near-Optimal Depth-Hierarchy Theorem for Small-Depth Multilinear Circuits

Suryajith Chillara, Christian Engels, Nutan Limaye, Srikanth Srinivasan

摘要:

我们研究了在多线性环境下,将积深度为$Δ+1$的代数电路转换为积深度为$Δ$的代数电路所需的尺寸爆破。我们发现,对于每一个积极的$Δ= Δ(n) = o(\log n/\log \log n),$有一个明确的多线性多项式$P^{(Δ)}$ $n$变量,可以计算的多线性公式的产品深度$Δ+1$和大小$O(n)$,但不是由任何多线性电路的产品深度$Δ$和大小小于$\exp(n^{Ω(1/Δ)})$。这一结果与所有$Δ= o(\log n/\log \log n).$的双指数中隐含的常数紧密相关。这加强了Raz和Yehudayoff的结果(计算复杂性2009),他们证明了常数深度多线性电路的拟多项式分离,以及Kayal的结果,奈尔和萨哈(STACS 2016)在$Δ= 1.$的情况下给出了指数分离。我们的分离例子可以看作是图可达性的变体的代数类似物。Chen,Oliveira,Servedio和Tan(STOC 2016)研究的问题,他们使用它们来证明常数深度布尔电路的下界。

英文摘要:

We study the size blow-up that is necessary to convert an algebraic circuit of product-depth $Δ+1$ to one of product-depth $Δ$ in the multilinear setting. We show that for every positive $Δ= Δ(n) = o(\log n/\log \log n),$ there is an explicit multilinear polynomial $P^{(Δ)}$ on $n$ variables that can be computed by a multilinear formula of product-depth $Δ+1$ and size $O(n)$, but not by any multilinear circuit of product-depth $Δ$ and size less than $\exp(n^{Ω(1/Δ)})$. This result is tight up to the constant implicit in the double exponent for all $Δ= o(\log n/\log \log n).$ This strengthens a result of Raz and Yehudayoff (Computational Complexity 2009) who prove a quasipolynomial separation for constant-depth multilinear circuits, and a result of Kayal, Nair and Saha (STACS 2016) who give an exponential separation in the case $Δ= 1.$ Our separating examples may be viewed as algebraic analogues of variants of the Graph Reachability problem studied by Chen, Oliveira, Servedio and Tan (STOC 2016), who used them to prove lower bounds for constant-depth Boolean circuits.

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