Time-space lower bounds for directed ST-connectivity on graph automata models

被引:2
作者
Barnes, G [1 ]
Edmonds, JA
机构
[1] Univ Waterloo, Dept Comp Sci, Waterloo, ON N2L 3G1, Canada
[2] Max Planck Inst Informat, Saarbrucken, Germany
[3] York Univ, Dept Comp Sci, N York, ON M3J 1P3, Canada
[4] Univ Toronto, Toronto, ON, Canada
关键词
time-space tradeoffs; lower bounds; JAG graph st-connectivity;
D O I
10.1137/S0097539795294402
中图分类号
TP301 [理论、方法];
学科分类号
081202 ;
摘要
Directed st-connectivity is the problem of detecting whether there is a path from a distinguished vertex s to a distinguished vertex t in a directed graph. We prove time-space lower bounds of ST = Omega(n2 log n/log(n log n/S) and S-1/2 T = Omega(m(n log n)(1/2)) for directed st-connectivity on Cook and Rackoff's jumping automaton for graphs (JAG) model [SIAM J. Comput., 9(1980), pp. 636-652], where n is the number of vertices and m the number of edges in the input graph, S is the space, and T the time used by the JAG. These lower bounds are simple and elegant, they approach the known upper bound of T = O(m) when S approaches Theta(n log n), and they are the first time-space tradeoffs for JAGs with an unrestricted number of jumping pebbles.
引用
收藏
页码:1190 / 1202
页数:13
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