Showing papers by "Ming-Yang Kao published in 1989"

Parallel depth-first search in general directed graphs

Abstract: A directed cycle separator of an n-vertex directed graph is a simple directed cycle such that when the vertices of the cycle are deleted, the resulting graph has no strongly connected component with more than n/2 vertices. This paper shows that the problem of finding a directed cycle separator is in randomized NC. The paper also proves that computing cycle separators and conducting depth-first search in directed graphs are deterministic NC-equivalent. These two results together yield the first RNC algorithm for depth-first search in directed graphs.

Local reorientation, global order, and planar topology

Abstract: Almost every problem on digraphs requires computing strongly connected components and directed spanning trees in one form or another. It has long been an open problem whether polylog time and linear processors are enough to find the strongly connected components of a digraph and compute directed spanning trees for these components. This paper provides the first non-trivial partial solution to this open problem: For a planar digraph with n vertices, the strongly connected components can be computed in O(log3n) time and O(n) processors. If the graph is strongly connected, a directed spanning tree can be built in O(log2n) time and O(n) processors. Both algorithms are deterministic and run on a parallel random access machine that allows concurrent reads and concurrent writes in its shared memory.