Hisao Tamaki - Profile on Academia.edu (original) (raw)
Papers by Hisao Tamaki
Old resolution with resolution
Journal of Combinatorial Optimization
Consider a dynamic programming scheme for a decision problem in which all subproblems involved ar... more Consider a dynamic programming scheme for a decision problem in which all subproblems involved are also decision problems. An implementation of such a scheme is positive-instance driven (PID), if it generates positive subproblem instances, but not negative ones, building each on smaller positive instances. We take the dynamic programming scheme due to Bouchitté and Todinca for treewidth computation, which is based on minimal separators and potential maximal cliques, and design a variant (for the decision version of the problem) with a natural PID implementation. The resulting algorithm performs extremely well: it solves a number of standard benchmark instances for which the optimal solutions have not previously been known. Incorporating a new heuristic algorithm for detecting safe separators, it also solves all of the 100 public instances posed by the exact treewidth track in PACE 2017, a competition on algorithm implementation. We describe the algorithm, prove its correctness, and give a running time bound in terms of the number of positive subproblem instances. We perform an experimental analysis which supports the practical importance of such a bound.
Route-Enabling Graph Orientation Problems
Proceedings of the 20th International Symposium on Algorithms and Computation, 2009
ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pair... more ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pairs, called st-pairs, we consider the problems of finding an orientation of all edges in G: min-sum orientation is to minimize the sum of the shortest directed distances between all st-pairs; and min-max orientation is to minimize the maximum shortest directed distance among all st-pairs. In this paper, we first show that both problems are strongly NP-hard for planar graphs even if all edge-weights are identical, and that both problems can be solved in polynomial time for cycles. We then consider the problems restricted to cacti, which form a graph class that contains trees and cycles but is a subclass of planar graphs. Then, min-sum orientation is solvable in polynomial time, whereas min-max orientation remains NP-hard even for two st-pairs. However, based on LP-relaxation, we present a polynomial-time 2-approximation algorithm for min-max orientation. Finally, we give a fully polynomial-time approximation scheme (FPTAS) for min-max orientation on cacti if the number of st-pairs is a fixed constant.
Fast Deflection Routing for Packets and Worms (Extended Summary)
Podc, 1993
Covering points in the plane by
Stoc, 1997
Algorithms for the Maximum Subarray Problem Based on Matrix Multiplication
Interdisciplinary Information Sciences, 2000
A Transformation System for Logic Programs which Preserves Equivalence
MAX/C on Sakai - A Web-based C-Programming Course
Transformational Logic Program Synthesis
Fgcs, 1984
ABSTRACT
A Characterization of Planar Graphs by Pseudo-Line Arrangements
Algorithmica, 2002
ABSTRACT
Approximation Algorithms for Geometric Optimization Problems(Special Issue on Algorithm Engineering : Surveys)
Ieice Transactions on Information and Systems, Mar 25, 2000
A generalized correctness proof of the unfold/ fold logic program transformation
A directed path-decomposition approach to exactly identifying attractors of boolean networks
2010 10th International Symposium on Communications and Information Technologies, 2010
Robust bounded-degree networks with small diameters
Proceedings of the fourth annual ACM symposium on Parallel algorithms and architectures - SPAA '92, 1992
A Linear Time Heuristic for the Branch-Decomposition of Planar Graphs
Lecture Notes in Computer Science, 2003
Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the ... more Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the bipartite graph on the sets of vertices and of faces of G such that each of its edges represents an incidence in G between a face and a vertex. Let α G denote the maximum distance in VF(G) from the outerface of G.
A Polynomial Time Algorithm for Bounded Directed Pathwidth
Lecture Notes in Computer Science, 2011
OLDT Resolution with Tabling
Lecture Notes in Computer Science, 2015
We call a digraph h-semicomplete if each vertex of the digraph has at most h non-neighbors, where... more We call a digraph h-semicomplete if each vertex of the digraph has at most h non-neighbors, where a non-neighbor of a vertex v is a vertex u = v such that there is no edge between u and v in either direction. This notion generalizes that of semicomplete digraphs which are 0-semicomplete and tournaments which are semicomplete and have no anti-parallel pairs of edges. Our results in this paper are as follows. (1) We give an algorithm which, given an h-semicomplete digraph G on n vertices and a positive integer k, in (h + 2k + 1) 2k n O(1) time either constructs a path-decomposition of G of width at most k or concludes correctly that the pathwidth of G is larger than k. (2) We show that there is a function f (k, h) such that every h-semicomplete digraph of pathwidth at least f (k, h) has a semicomplete subgraph of pathwidth at least k. One consequence of these results is that the problem of deciding if a fixed digraph H is topologically contained in a given h-semicomplete digraph G admits a polynomial-time algorithm for fixed h.
Interdisciplinary Information Sciences, 2000
Unfold/fold transformations of logic programs
Old resolution with resolution
Journal of Combinatorial Optimization
Consider a dynamic programming scheme for a decision problem in which all subproblems involved ar... more Consider a dynamic programming scheme for a decision problem in which all subproblems involved are also decision problems. An implementation of such a scheme is positive-instance driven (PID), if it generates positive subproblem instances, but not negative ones, building each on smaller positive instances. We take the dynamic programming scheme due to Bouchitté and Todinca for treewidth computation, which is based on minimal separators and potential maximal cliques, and design a variant (for the decision version of the problem) with a natural PID implementation. The resulting algorithm performs extremely well: it solves a number of standard benchmark instances for which the optimal solutions have not previously been known. Incorporating a new heuristic algorithm for detecting safe separators, it also solves all of the 100 public instances posed by the exact treewidth track in PACE 2017, a competition on algorithm implementation. We describe the algorithm, prove its correctness, and give a running time bound in terms of the number of positive subproblem instances. We perform an experimental analysis which supports the practical importance of such a bound.
Route-Enabling Graph Orientation Problems
Proceedings of the 20th International Symposium on Algorithms and Computation, 2009
ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pair... more ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pairs, called st-pairs, we consider the problems of finding an orientation of all edges in G: min-sum orientation is to minimize the sum of the shortest directed distances between all st-pairs; and min-max orientation is to minimize the maximum shortest directed distance among all st-pairs. In this paper, we first show that both problems are strongly NP-hard for planar graphs even if all edge-weights are identical, and that both problems can be solved in polynomial time for cycles. We then consider the problems restricted to cacti, which form a graph class that contains trees and cycles but is a subclass of planar graphs. Then, min-sum orientation is solvable in polynomial time, whereas min-max orientation remains NP-hard even for two st-pairs. However, based on LP-relaxation, we present a polynomial-time 2-approximation algorithm for min-max orientation. Finally, we give a fully polynomial-time approximation scheme (FPTAS) for min-max orientation on cacti if the number of st-pairs is a fixed constant.
Fast Deflection Routing for Packets and Worms (Extended Summary)
Podc, 1993
Covering points in the plane by
Stoc, 1997
Algorithms for the Maximum Subarray Problem Based on Matrix Multiplication
Interdisciplinary Information Sciences, 2000
A Transformation System for Logic Programs which Preserves Equivalence
MAX/C on Sakai - A Web-based C-Programming Course
Transformational Logic Program Synthesis
Fgcs, 1984
ABSTRACT
A Characterization of Planar Graphs by Pseudo-Line Arrangements
Algorithmica, 2002
ABSTRACT
Approximation Algorithms for Geometric Optimization Problems(Special Issue on Algorithm Engineering : Surveys)
Ieice Transactions on Information and Systems, Mar 25, 2000
A generalized correctness proof of the unfold/ fold logic program transformation
A directed path-decomposition approach to exactly identifying attractors of boolean networks
2010 10th International Symposium on Communications and Information Technologies, 2010
Robust bounded-degree networks with small diameters
Proceedings of the fourth annual ACM symposium on Parallel algorithms and architectures - SPAA '92, 1992
A Linear Time Heuristic for the Branch-Decomposition of Planar Graphs
Lecture Notes in Computer Science, 2003
Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the ... more Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the bipartite graph on the sets of vertices and of faces of G such that each of its edges represents an incidence in G between a face and a vertex. Let α G denote the maximum distance in VF(G) from the outerface of G.
A Polynomial Time Algorithm for Bounded Directed Pathwidth
Lecture Notes in Computer Science, 2011
OLDT Resolution with Tabling
Lecture Notes in Computer Science, 2015
We call a digraph h-semicomplete if each vertex of the digraph has at most h non-neighbors, where... more We call a digraph h-semicomplete if each vertex of the digraph has at most h non-neighbors, where a non-neighbor of a vertex v is a vertex u = v such that there is no edge between u and v in either direction. This notion generalizes that of semicomplete digraphs which are 0-semicomplete and tournaments which are semicomplete and have no anti-parallel pairs of edges. Our results in this paper are as follows. (1) We give an algorithm which, given an h-semicomplete digraph G on n vertices and a positive integer k, in (h + 2k + 1) 2k n O(1) time either constructs a path-decomposition of G of width at most k or concludes correctly that the pathwidth of G is larger than k. (2) We show that there is a function f (k, h) such that every h-semicomplete digraph of pathwidth at least f (k, h) has a semicomplete subgraph of pathwidth at least k. One consequence of these results is that the problem of deciding if a fixed digraph H is topologically contained in a given h-semicomplete digraph G admits a polynomial-time algorithm for fixed h.
Interdisciplinary Information Sciences, 2000
Unfold/fold transformations of logic programs