Edward A. Hirsch and Arist Kojevnikov. UnitWalk: A new SAT solver that uses local search guided by unit clause elimination. PDMI preprint 9/2001, Steklov Institute of Mathematics at St.Petersburg, 2001.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....very simple hill climber GSAT [23] and its powerful variant Walksat [22] are famous examples of incomplete algorithms. Though incomplete algorithms are little helpful for unsatis able instances, they represent the unique approach for nding models of very large instances. At this time, Unitwalk [14] appears as the best incomplete algorithm. A current trend for designing more powerful algorithms consists in combining in some way the best elements from di erent approaches, leading to hybrid algorithms [21] In this paper, we present GASAT, a new hybrid algorithm embedding a tabu search ....

.... simplify our TS function as TS(X;Maxf lip) 4 Experimental Results In this section, we evaluate the performance of GASAT on several classes of satis able and unsatis able benchmark instances and compare it with Walksat [22] one of the well known incomplete algorithms for SAT, and with UnitWalk [14] (combination of local search and unit propagation) the best up to now incomplete randomized solver presented to the SAT2002 competition [24] 4.1 Experimental Conditions Due to the incomplete and non deterministic nature of GASAT, Walksat and UnitWalk, each algorithm runs 20 times on each ....

Edward A. Hirsch and Arist Kojevnikov. UnitWalk: A new SAT solver that uses local search guided by unit clause elimination. PDMI preprint 9/2001, Steklov Institute of Mathematics at St.Petersburg, 2001.

....accelerated development of new circuits. Initial work to develop automatic SAT solving programs primarily focuses on the Davis Putname Longemann Loveland (DPLL) algorithm [5] for solving SAT instances. Solutions to practical problems, however, remained difficult to achieve. More recent research [1,3,8,9] has resulted in algorithmic and implementation advances that make it possible to solve problem instances generated by practical applications. Because of the importance of SAT results to the engineering community, a suite of benchmark [14] problems (some with known solutions some not) has been ....

E. A. Hirsch and A. Kojevnikov. UnitWalk: A new SAT solver that uses local search guided by unit clause elimination. In PDMI preprint 9/2001.

....namely, GSAT [15] and WalkSAT [12] 14] They both have many variations, for example, GWSAT [14] GSAT Tabu [11] of GSAT, and Novelty, R Novelty [12] Novelty , and R Novelty [6] of WalkSAT. Recently, two more e ective local search methods have been proposed, they are: SDF [13] and UnitWalk [5]. Generally speaking, SDF makes a greedy descent on its objective function similar to other local search methods. But a special feature of SDF is that it not only counts the number of unsatis ed clauses, but also considers how strongly a clause is satis ed. In addition, SDF makes the use of a ....

....4.3. In an instance of Uniform Random 3 SAT problems, each clause has exactly 3 literals which are randomly selected from n variables and randomly decide whether add them or their negations to this clause. In an instance of at100, clauses may have di erent number of literals, but at most 3. In [5], the authors presented their experimental results on benchmark SAT problem packages, include the above two packages. To compare with those of other algorithms, we conducted the same experiments on each package using the MASSAT approach. In Table 1, we list the mean and median numbers of movements ....

[Article contains additional citation context not shown here]

E. A. Hirsch and A. Kojevnikov, UnitWalk: A new SAT solver that uses local search guided by unit clause elimination, in Proceedings of the 5th International Symposium on the Theory and Applications of Satis ability Testing (SAT 2002), pp. 35-42, 2002.

....SATs. The conventional methods can be categorized into two types. The rst type is based on DPLL procedure [3, 4] for example, GRASP [13] REL SAT [11] SATZ [12] and TABLEAU [2] etc. Another type is based on local search [5, 20] such as GSAT [20] WalkSAT [14, 19] SDF [17, 18] and UnitWalk [8, 9]. All these conventional methods are sequential. Recently, two distributed multi agent based approaches have been proposed to solve SATs, i.e. MASSAT [10] and MultiDB [7] In both distributed approaches, the authors employed a multi agent system to solve SATs in which agents were used to ....

E. A. Hirsch and A. Kojevnikov. Unitwalk: A new sat solver that uses local search guided by unit clause elimination. In Proceedings of the Fifth International Symposium on the Theory and Applications of Satis ability Testing (SAT 2002.

....that these di erences are essential. 1. Our algorithm is probabilistically approximately complete (see Theorem 1) while WalkSAT TABU is essentially incomplete [13, 14] 2. Experimental data show that UnitWalk makes substantially less ips than WalkSAT TABU on almost all instances (see tables in [12]) 4. The solver The algorithm described in Section 3 is interesting in its own right. However, life is always more complex than theory. Therefore, writing a solver that performs well if run on a real computer is another kind of art. In particular, one has to implement ecient data structures, ....

Hirsch, E. A. and A. Kojevnikov: 2001, `UnitWalk: A new SAT solver that uses local search guided by unit clause elimination'. PDMI preprint 9/2001, Steklov Institute of Mathematics at St.Petersburg.

....When removing clauses Berkmin tries to get rid of the clauses that are at the bottom of the stack in the first place. Eugene Goldberg] The version used for the competition was 62. Berkmin 56 binaries are available at http: eigold.tripod.com . unitwalk by Edward A. Hirsch and Arist Kojevnikov [HK01] Incomplete randomized solver. UnitWalk is a combination of unit clause elimination (particularly, the idea of Paturi, Pudlak and Zane s randomized unit clause elimination algorithm [PPZ97] and local search. The solver participated in the competition extends this basic algorithm with adding ....

E. A. Hirsch and A. Kojevnikov. UnitWalk: A new SAT solver that uses local search guided by unit clause elimination. PDMI preprint 9/2001, Steklov Institute of Mathematics at St.Petersburg, 2001. A journal version is submitted to this issue.

.... approximately complete (PAC) 1 Introduction Since this extended abstract is aimed at SAT Symposium, we skip most de nitions and history concerning the Boolean satis ability problem (SAT) Concerning these topics we refer the interested reader to the preliminary full version of our paper [HK01]. Weakly exponential worst case upper bounds. Weakly exponential upper bounds on the worst case running time of SAT algorithms are bounds of the form p(n)c , where c 2 is a constant, n is the number of variables in the input formula, and p is a polynomial (note that SAT can be easily ....

....instances and on structured instances encoding various practical problems like planning or circuit design. Theoretical knowledge about these algorithms is very limited and mostly concentrates on exponential worst case lower bounds [Hir00] average case bounds [GG94,KP92] or properties See also [HK01] for a more detailed preliminary version. Supported by CRDF and by grant #1 of the 6th RAS contest expertise of young scientists projects (1999) Supported by CRDF. 35 related to their completeness [CGH00,Hoo98,Hoo99] Some of these algorithms are surveyed in [GPFW97,HS00a] In ....

[Article contains additional citation context not shown here]

Edward A. Hirsch and Arist Kojevnikov. UnitWalk: A new SAT solver that uses local search guided by unit clause elimination. PDMI preprint 9/2001, Steklov Institute of Mathematics at St.Petersburg, 2001.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC