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arXiv 1409.6397cs.CG
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空等边三角形定义的德洛内三角剖分上的局部最优布线

Optimal local routing on Delaunay triangulations defined by empty equilateral triangles

Prosenjit Bose, Rolf Fagerberg, André van Renssen, Sander Verdonschot

摘要:

我们提出了一个确定性的本地路由算法,保证找到一条路径之间的任何一对顶点之间的半- $θ_6$ -图(半- $θ_6$ -图是等价的德洛内三角剖分的空区域是一个等边三角形)。路径的长度最多是顶点对之间的欧几里得距离的$5/\sqrt{3} \approx 2.887$倍。此外,我们表明,没有本地路由算法可以实现更好的路由比,从而证明我们的路由算法是最佳的。这有点令人惊讶,因为半$θ_6$图的生成比是2,这意味着即使总是存在一条长度至多为欧几里得距离两倍的路径,我们也不能总是在本地路由时找到这样的路径。由于每一个三角形可以嵌入在平面上作为一个半$θ_6$ -图使用$O(\log n)$位每顶点坐标通过Schnyder的嵌入方案(SODA 1990),我们的结果提供了一个有竞争力的本地路由算法,为每个这样的嵌入三角形。最后,我们展示了如何我们的路由算法可以适应于提供路由比的$15/\sqrt{3} \approx 8.660$上的两个有界度的子图的半- $θ_6$ -图。

英文摘要:

We present a deterministic local routing algorithm that is guaranteed to find a path between any pair of vertices in a half-$θ_6$-graph (the half-$θ_6$-graph is equivalent to the Delaunay triangulation where the empty region is an equilateral triangle). The length of the path is at most $5/\sqrt{3} \approx 2.887$ times the Euclidean distance between the pair of vertices. Moreover, we show that no local routing algorithm can achieve a better routing ratio, thereby proving that our routing algorithm is optimal. This is somewhat surprising because the spanning ratio of the half-$θ_6$-graph is 2, meaning that even though there always exists a path whose lengths is at most twice the Euclidean distance, we cannot always find such a path when routing locally. Since every triangulation can be embedded in the plane as a half-$θ_6$-graph using $O(\log n)$ bits per vertex coordinate via Schnyder's embedding scheme (SODA 1990), our result provides a competitive local routing algorithm for every such embedded triangulation. Finally, we show how our routing algorithm can be adapted to provide a routing ratio of $15/\sqrt{3} \approx 8.660$ on two bounded degree subgraphs of the half-$θ_6$-graph.

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