论文标题

$δ$ - 最佳空间中的近乎最佳搜索时间,反之亦然

Near-Optimal Search Time in $δ$-Optimal Space, and Vice Versa

论文作者

Kociumaka, Tomasz, Navarro, Gonzalo, Olivares, Francisco

论文摘要

储层计算是预测湍流的有力工具,其简单的架构具有处理大型系统的计算效率。然而,其实现通常需要完整的状态向量测量和系统非线性知识。我们使用非线性投影函数将系统测量扩展到高维空间,然后将其输入到储层中以获得预测。我们展示了这种储层计算网络在时空混沌系统上的应用,该系统模拟了湍流的若干特征。我们表明,使用径向基函数作为非线性投影器,即使只有部分观测并且不知道控制方程,也能稳健地捕捉复杂的系统非线性。最后,我们表明,当测量稀疏、不完整且带有噪声,甚至控制方程变得不准确时,我们的网络仍然可以产生相当准确的预测,从而为实际湍流系统的无模型预测铺平了道路。

Two recent lower bounds on the compressibility of repetitive sequences, $δ\le γ$, have received much attention. It has been shown that a length-$n$ string $S$ over an alphabet of size $σ$ can be represented within the optimal $O(δ\log\tfrac{n\log σ}{δ\log n})$ space, and further, that within that space one can find all the $occ$ occurrences in $S$ of any length-$m$ pattern in time $O(m\log n + occ \log^εn)$ for any constant $ε>0$. Instead, the near-optimal search time $O(m+({occ+1})\log^εn)$ has been achieved only within $O(γ\log\frac{n}γ)$ space. Both results are based on considerably different locally consistent parsing techniques. The question of whether the better search time could be supported within the $δ$-optimal space remained open. In this paper, we prove that both techniques can indeed be combined to obtain the best of both worlds: $O(m+({occ+1})\log^εn)$ search time within $O(δ\log\tfrac{n\log σ}{δ\log n})$ space. Moreover, the number of occurrences can be computed in $O(m+\log^{2+ε}n)$ time within $O(δ\log\tfrac{n\log σ}{δ\log n})$ space. We also show that an extra sublogarithmic factor on top of this space enables optimal $O(m+occ)$ search time, whereas an extra logarithmic factor enables optimal $O(m)$ counting time.

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