This is the third of three papers describing ZAP, a satisfiability engine that substantially generalizes existing tools while retaining the performance characteristics of modern high-performance solvers. The fundamental idea underlying ZAP is that many problems passed to such engines contain rich internal structure that is obscured by the Boolean representation used; our goal has been to define a representation in which this structure is apparent and can be exploited to improve computational performance. The first paper surveyed existing work that (knowingly or not) exploited problem structure to improve the performance of satisfiability engines, and the second paper showed that this structure could be understood in terms of groups of permutations acting on individual clauses in any particular Boolean theory. We conclude the series by discussing the techniques needed to implement our ideas, and by reporting on their performance on a variety of problem instances.

This is the second of three planned papers describing ZAP, a satisfiability engine that substantially generalizes existing tools while retaining the performance characteristics of modern high performance solvers. The fundamental idea underlying ZAP is that many problems passed to such engines contain rich internal structure that is obscured by the Boolean representation used; our goal is to define a representation in which this structure is apparent and can easily be exploited to improve computational performance. This paper presents the theoretical basis for the ideas underlying ZAP, arguing that existing ideas in this area exploit a single, recurring structure in that multiple database axioms can be obtained by operating on a single axiom using a subgroup of the group of permutations on the literals in the problem. We argue that the group structure precisely captures the general structure at which earlier approaches hinted, and give numerous examples of its use. We go on to extend the Davis-Putnam-Logemann-Loveland inference procedure to this broader setting, and show that earlier computational improvements are either subsumed or left intact by the new method. The third paper in this series discusses ZAP's implementation and presents experimental performance results.

For an integer constant d > 0, let Γd denote the class of finite groups all of whose nonabelian composition factors lie in Sd; in particular, Γd includes all solvable groups. Motivated by applications to graph-isomorphism testing, there has been extensive study of the complexity of computation for permutation groups in this class. In particular, set-stabilizers, group intersections, and centralizers have all been shown to be polynomial-time computable. The most notable gap in the theory has been the question of whether normalizers of subgroups can be found in polynomial time. We resolve this question in the affirmative. Among other new procedures, the algorithm requires instances of subspace-stabilizers for certain linear representations and therefore some polynomial-time computation in matrix groups.

We show that hypergraph isomorphism can be tested in time O(c"),where n is the sire of the vertex set.In general, input of a hypergraph could require n(2") space, in which

We present new algorithms for permutation group manipulation. Our methods result in an improvement of nearly an order of magnitude in the worst-case analysis for the fundamental problems of finding strong generating sets and testing membership. The normal structure of the group is brought into play even for such elementary issues. An essential element is the recognition of large alternating composition factors of the given group and subsequent extension of the permutation domain to display the natural action of these alternating groups. Further new features include a novel fast handling of alternating groups and the sifting of defining relations in order to link these and other analyzed factors with the rest of the group. The analysis of the algorithm depends on the classification of finite simple groups. In a sequel to this paper, using an enhancement of the present method, we shall achieve a further order of magnitude improvement.

Article Computing normalizers in permutation p-groups Share on Authors: Eugene M. Luks Computer and Information Science, University of Oregon Computer and Information Science, University of OregonView Profile , Ferenc Rákóczi Computer and Information Science, University of Oregon Computer and Information Science, University of OregonView Profile , Charles R. B. Wright Department of Mathematics, University of Oregon Department of Mathematics, University of OregonView Profile Authors Info & Claims ISSAC '94: Proceedings of the international symposium on Symbolic and algebraic computationAugust 1994 Pages 139–146https://doi.org/10.1145/190347.190390Published:01 August 1994 2citation179DownloadsMetricsTotal Citations2Total Downloads179Last 12 Months1Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

The author announces methods for efficient management of solvable matrix groups over finite fields. He shows that solvability and nilpotence can be tested in polynomial-time. Such efficiency seems unlikely for membership-testing, which subsumes the discrete-log problem. However, assuming that the primes in mod G mod (other than the field characteristic) are polynomially-bounded, membership-testing and many other computational problems are in polynomial time. These problems include finding stabilizers of vectors and of subspaces and finding centralizers and intersections of subgroups. An application to solvable permutation groups puts the problem of finding normalizers of subgroups into polynomial time. Some of the results carry over directly to finite matrix groups over algebraic number fields; thus, testing solvability is in polynomial time, as is testing membership and finding Sylow subgroups.>

Article Free Access Share on Fast Monte Carlo algorithms for permutation groups Authors: László Babai Univ. of Chicago, Chicago, IL Univ. of Chicago, Chicago, ILView Profile , Gene Cooperman Northeastern Univ., Boston, MA Northeastern Univ., Boston, MAView Profile , Larry Finkelstein Northeastern Univ., Boston, MA Northeastern Univ., Boston, MAView Profile , Eugene Luks Univ. of Oregon, Eugene Univ. of Oregon, EugeneView Profile , Ákos Seress Ohio State Univ., Columbus Ohio State Univ., ColumbusView Profile Authors Info & Claims STOC '91: Proceedings of the twenty-third annual ACM symposium on Theory of ComputingJanuary 1991 Pages 90–100https://doi.org/10.1145/103418.103435Published:03 January 1991Publication History 14citation519DownloadsMetricsTotal Citations14Total Downloads519Last 12 Months55Last 6 weeks5 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

We present polynomial-time algorithms for computation in quotient groups G/K of a permutation group G.In effect, these solve, for quotient groups, the problems that are known to be in polynomial-time for permutation groups.Since it is not computationally feasible to represent G/K itself as a permutation group, the methodology for the quotient-group versions of such problems frequently differ markedly from the procedures that have been observed for the K = 1 subcases.Whereas the algorithms for permutation groups may have rested on elementary notions, procedures underlying the extension to quotient groups often utilize deep knowledge of the structure of the group.In some instances, we present algorithms for problems that were not previously known to be in polynomial time, even for permutation groups themselves (K = 1).These problems apparently required access to quotients.

The construction of point stabilizer subgroups is a problem which has been studied intensively. [1, 4, 5, 10, 11, 12, 14] This work describes a general reduction of certain group constructions to the point stabilizer problem. Examples are given for the centralizer, the normal closure, and a restricted group intersection problem. For the normal closure problem, this work provides an alternative to current algorithms, which are limited by the need for repeated closures under conjugation. For the centralizer and restricted group intersection problems, one can use an existing point stabilizer sequence along with a recent base change algorithm [2] to avoid generating a new point stabilizer sequence. This reduces the time complexity by at least an order of magnitude. Algorithms and theoretical time estimates for the special case of a small base are also summarized. An implementation is in progress.

Novel algorithms for computation in permutation groups are presented. They provide an order-of-magnitude improvement in the worst-case analysis of the basic permutation-group problems, including membership testing and computing the order of the group. For deeper questions about the group, including finding composition factors, an improvement of up to four orders of magnitude is realized. These and other essential investigations are all accomplished in O(n/sup 4/log/sup c/n) time. The approach is distinguished by its recognition and use of the intrinsic structure of the group at hand.>

We show that the basic problems of permutation group manipulation admit efficient parallel solutions. Given a permutation group G by a list of generators, we find a set of NC-efficient strong generators in NC. Using this, we show, that the following problems are in NC: membership in G; determining the order of G; finding the center of G; finding a composition series of G along with permutation representations of each composition factor. Moreover, given G, we are able to find the pointwise stabilizer of a set in NC. One consequence is that isomorphism of graphs with bounded multiplicity of eigenvalues is in NC.

This paper describes an O ( n 3 log n ) deterministic algorithm and an O ( n 3 ) Las Vegas algorithm for testing whether two given trivalent graphs on n vertices are isomorphic. In fact, the algorithms construct the set of all isomorphisms between two such graphs, presenting, in particular, generators for the group of all automorphisms of a trivalent graph. The algorithms are based upon the original polynomial-time solution to these problems by Luks but they introduce numerous speedups. These include improved permutation-group algorithms that exploit the structure of the underlying 2-groups. A remarkable property of the Las Vegas algorithm is that it computes the set of all isomorphisms between two trivalent graphs for the cost of computing only those isomorphisms that map a specified edge to a specified edge.

We develop parallel techniques for dealing with permutation group problems. These are most effective on the class of groups with bounded non-abelian composition factors. For this class, we place in NC problems such as membership testing, finding the center and composition factors, and, of particular significance, finding pointwise-set-stabilisers. The last has applications to instances of graph-isomorphism and we show that NC contains isomorphism-testing for vertex-colored graphs with bounded color multiplicity, a problem not long known to be in polynomial time.

We develop fast parallel solutions to a number of basic problems involving solvable and nilpotent permutation groups. Testing solvability is in NC, and RNC includes, for solvable groups, finding order, testing membership, finding the derived series and finding a composition series. Additionally, for nilpotent groups, one can, in RNC, find the center, a central composition series, and point-wise stabilizers of sets. There are applications to graph isomorphism. In fact, we exhibit a class of vertex-colored graphs for which determining isomorphism is NC-equivalent to computing ranks of matrices Over small fields. A useful tool is the observation that the problem of finding the smallest subspace containing a given set of vectors and closed under a given set of linear transformations (all over a small field) belongs to RNC.

We address the graph isomorphism problem and related fundamental complexity problems of computational group theory. The main results are these: A1. A polynomial time algorithm to test simplicity and find composition factors of a given permutation group (COMP). A2. A polynomial time algorithm to find elements of given prime order p in a permutation group of order divisible by p. A3. A polynomial time reduction of the problem of finding Sylow subgroups of permutation groups (SYLFIND) to finding the intersection of two cosets of permutation groups (INT). As a consequence, one can find Sylow subgroups of solvable groups and of groups with bounded nonabelian composition factors in polynomial time. A4. A polynomial time algorithm to solve SYLFIND for finite simple groups. A5. An ncd/log d algorithm for isomorphism (ISO) of graphs of valency less than d and a consequent improved moderately exponential general graph isomorphism test in exp(c√n log n) steps. A6. A moderately exponential, n,c√n algorithm for INT. Combined with A3, we obtain an nc√n algorithm for SYLFIND as well. All these problems have strong links to each other. ISO easily reduces to INT. A subcase of SYLFIND was solved in polynomial time and applied to bounded valence ISO in [Lul]. Now, SYLFIND is reduced to INT. Interesting special cases of SYLFIND belong to NP ∩ coNP and are not known to have subexponential solutions. All the results stated depend on the classification of finite simple groups. We note that no previous ISO test had no(d) worst case behavior for graphs of valency less than d. It appears that unless there is another radical breakthrough in ISO, independent of the previous one, the simple groups classification is an indispensable tool for further developments.

We announce an algebraic approach to the problem of assigning canonical forms to graphs. We compute canonical forms and the associated canonical labelings (or renumberings) in polynomial time for graphs of bounded valence, in moderately exponential, exp(n½ + ο(1)),time for general graphs, in subexponential, nlog n, time for tournaments and for 2-(ν,κ,λ) block designs with κ,λ bounded and nlog log n time for λ-planes (symmetric designs) with λ bounded. We prove some related problems NP-hard and indicate some open problems.

The main results of this paper are an O(n3) probabilistic algorithm and an O(n3 log n) deterministic algorithm that test whether two given trivalent graphs are isomorphic. In fact, the algorithms construct the set of all isomorphisms of the two graphs. Variants of these algorithms construct the set of all automorphisms of a trivalent graph. The algorithms make use of some new improved permutation group algorithms that exploit the fact that the groups involved are 2-groups. A remarkable property of the probabilistic algorithm is that it computes Isoe,ei(X,Y), i = 1,...,m, m = O(n) (the set of all isomorhisms φ: X → Y with φ(e)=ei) for the cost of computing the single set Isoe,el(X,Y).

A permutation group on n letters may always be represented by a small set of generators, even though its size may be exponential in n. We show that it is practical to use such a representation since many problems such as membership testing, equality testing, and inclusion testing are decidable in polynomial time. In addition, we demonstrate that the normal closure of a subgroup can be computed in polynomial time, and that this proceaure can be used to test a group for solvability. We also describe an approach to computing the intersection of two groups. The procedures and techniques have wide applicability and have recently been used to improve many graph isomorphism algorithms.

Suppose we are given a set of generators for a group G of permutations of a colored set A. The color automorphism problem for G involves finding generators for the subgroup of G which stabilizes the color classes. Testing isomorphism of graphs of valence ≤ t is polynomial-time reducible to the color automorphism problem for groups with small simple sections. The algorithm for the latter problem involves several divide-and-conquer tricks. The problem is solved sequentially on the G-orbits. An orbit is broken into a minimal set of blocks permuted by G. The hypothesis on G guarantees the existence of a 'large' subgroup P which acts as a p-group on the blocks. A similar process is repeated for each coset of P on G. Some results on primitive permutation groups are used to show that the algorithm runs in polynomial time.