scholarly journals An Adaptive Strategy for Tuning Duplicate Trails in SAT Solvers

Symmetry ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 197
Author(s):  
Wenjing Chang ◽  
Yang Xu ◽  
Shuwei Chen
Keyword(s):  
Adaptive Strategy ◽  
Empirical Results ◽  
Sat Solvers ◽  
Decision Variables ◽  
Before And After ◽  
New Strategy ◽  
Clause Learning ◽  
Restart Strategy

In mainstream conflict driven clause learning (CDCL) solvers, because of frequent restarts and phase saving, there exists a large proportion of duplicate assignment trails before and after restarts, resulting in unnecessary time wastage during solving. This paper proposes a new strategy—identifying those duplicate assignments trails and dealing with them by changing the sort order. This approach’s performance is compared with that of the Luby static restart scheme and a dynamic Glucose-restart strategy. We show that the number of solved instances is increased by 3.2% and 4.6%. We also make a compassion with the MapleCOMSPS solver by testing against application benchmarks from the SAT Competitions 2015 to 2017. These empirical results provide further evidence of the benefits of the proposed heuristic, having the advantage of managing duplicate assignments trails and choosing appropriate decision variables adaptively.

scholarly journals Seeking Practical CDCL Insights from Theoretical SAT Benchmarks

2018 ◽  
Author(s):  
Jan Elffers ◽  
Jesús Giráldez-Cru ◽  
Stephan Gocht ◽  
Jakob Nordström ◽  
Laurent Simon
Keyword(s):  
Systematic Study ◽  
Boolean Satisfiability ◽  
Proof System ◽  
Sat Solvers ◽  
Proof Search ◽  
Wide Range ◽  
Clause Learning ◽  
Resolution Proof ◽  
Shed Light

Over the last decades Boolean satisfiability (SAT) solvers based on conflict-driven clause learning (CDCL) have developed to the point where they can handle formulas with millions of variables. Yet a deeper understanding of how these solvers can be so successful has remained elusive. In this work we shed light on CDCL performance by using theoretical benchmarks, which have the attractive features of being a) scalable, b) extremal with respect to different proof search parameters, and c) theoretically easy in the sense of having short proofs in the resolution proof system underlying CDCL. This allows for a systematic study of solver heuristics and how efficiently they search for proofs. We report results from extensive experiments on a wide range of benchmarks. Our findings include several examples where theory predicts and explains CDCL behaviour, but also raise a number of intriguing questions for further study.

Chapter 3. Complete Algorithms

2021 ◽  
Author(s):  
Adnan Darwiche ◽  
Knot Pipatsrisawat
Keyword(s):  
Real World ◽  
Theoretical Perspective ◽  
Point Of View ◽  
Sat Solving ◽  
Practical Point ◽  
Sat Solvers ◽  
Proof Systems ◽  
Real World Applications ◽  
Clause Learning

Complete SAT algorithms form an important part of the SAT literature. From a theoretical perspective, complete algorithms can be used as tools for studying the complexities of different proof systems. From a practical point of view, these algorithms form the basis for tackling SAT problems arising from real-world applications. The practicality of modern, complete SAT solvers undoubtedly contributes to the growing interest in the class of complete SAT algorithms. We review these algorithms in this chapter, including Davis-Putnum resolution, Stalmarck’s algorithm, symbolic SAT solving, the DPLL algorithm, and modern clause-learning SAT solvers. We also discuss the issue of certifying the answers of modern complete SAT solvers.

scholarly journals PO 7151 COMPARING TWO BED NET DELIVERY MODELS IN’RURAL DISTRICTS OF MOZAMBIQUE

2019 ◽  
Vol 4 (Suppl 3) ◽  
pp. A19.3-A19
Author(s):  
Jorge Arroz
Keyword(s):  
Cost Effectiveness ◽  
Implementation Strategies ◽  
Cost Effective ◽  
Universal Coverage ◽  
Bed Net ◽  
Net Benefit ◽  
Previous Night ◽  
Before And After ◽  
New Strategy ◽  
Delivery Models

BackgroundThe use of long-lasting insecticidal nets (LLINs) is associated with a reduction in malaria transmission. In 2015, a new delivery strategy (intervention) for universal coverage campaign was tested and compared with standard strategy (control). The objective is to compare two bed net delivery models in rural districts of Mozambique.MethodsTwo districts served as intervention, and two as control. The following study design was used: 1) before and after; and 2) cost-effectiveness analysis. Three core implementation strategies were tested: 1) use of coupons during household registration, 2) use of stickers to identify registered houses, and 3) a new LLINs allocation criterion. The main endpoints measured were: i) percentage of distributed LLINs; ii) LLINs ownership and use coverage; iii) percentage of households that achieved universal coverage; iv) incremental cost-effectiveness ratio (ICER); v) incremental net benefit (INB).ResultsApproximately 88% (302,648) of LLINs were distributed in intervention districts compared to 77% (219,613) in control districts [OR: 2.14 (95% CI: 2.11–2.16)]. Six months after the 2015 campaign, 98.8% of the 760 households surveyed in the intervention districts had at least one LLIN; 89.6% of the 787 households surveyed in the control districts had at least one LLIN [OR: 9.7, (95% CI: 5.25–22.76)]. Near 95% and 87% of respondents who had at least one LLIN, reported having slept under the LLIN the previous night in the intervention and control districts, respectively [OR: 3.2; (95% CI 2.12–4.69)]; 71% of the households surveyed achieved universal coverage in the intervention districts against 59.6% in the control districts [OR: 1.6; (95% CI: 1.33–2.03)]. ICER per distributed LLIN was US$ 0.68. INB was positive.ConclusionIntervention districts had greater LLINs availability, greater LLINs ownership and use coverage, and a better progression toward reaching universal coverage targets. The new strategy was more cost-effective than the previous strategy.

A Study on the Strategic Application of Abnormal Risk-Return Relationship

2017 ◽  
Vol 25 (3) ◽  
pp. 339-367
Author(s):  
Youngmin Choi ◽  
Bohyun Yoon
Keyword(s):  
Capital Market ◽  
Efficient Frontier ◽  
Investment Strategies ◽  
Traditional Concept ◽  
Period Analysis ◽  
Empirical Results ◽  
Risk Return ◽  
High Return ◽  
Before And After ◽  
Preliminary Study

This paper focuses on the strategic application based on the empirical results of risk-return relationship against the classical concept. Empirical analysis from domestic data, we verify that the traditional concept-‘high risk, high return’ relationship are maintained, however, we confirm the falling pattern in the highest total volatility group. Even though we implies double sorting method to control the well known systematic factor such as BM and size, we still confirm such abnormal risk-return relationship. Furthermore, we perform sub-period analysis before and after the liberalization of Korean capital market and we find such abnormal risk-return relationship is appeared after the liberalization. Based on our empirical results, we establish and verify the new benchmark that evenly allocate highest volatility portfolio to sub-volatility portfolio. Under the new benchmark, we confirm the expansion of the efficient frontier and the improvement of Sharpe ratio. We believe that our results provide an applicability research of smart beta strategy and new benchmark based on such strategy. We expect our research to be used as preliminary study to overcome the era of “new normal” and to reform the investment strategies correspond to segmentation of benchmark.

scholarly journals FourierSAT: A Fourier Expansion-Based Algebraic Framework for Solving Hybrid Boolean Constraints

2020 ◽  
Vol 34 (02) ◽  
pp. 1552-1560
Author(s):  
Anastasios Kyrillidis ◽  
Anshumali Shrivastava ◽  
Moshe Vardi ◽  
Zhiwei Zhang
Keyword(s):  
Boolean Functions ◽  
Continuous Optimization ◽  
Conjunctive Normal Form ◽  
Cardinality Constraints ◽  
Sat Solvers ◽  
Boolean Satisfiability Problem ◽  
Algebraic Framework ◽  
Clause Learning ◽  
Sat Solver ◽  
Analysis Of Boolean Functions

The Boolean SATisfiability problem (SAT) is of central importance in computer science. Although SAT is known to be NP-complete, progress on the engineering side—especially that of Conflict-Driven Clause Learning (CDCL) and Local Search SAT solvers—has been remarkable. Yet, while SAT solvers, aimed at solving industrial-scale benchmarks in Conjunctive Normal Form (CNF), have become quite mature, SAT solvers that are effective on other types of constraints (e.g., cardinality constraints and XORs) are less well-studied; a general approach to handling non-CNF constraints is still lacking. In addition, previous work indicated that for specific classes of benchmarks, the running time of extant SAT solvers depends heavily on properties of the formula and details of encoding, instead of the scale of the benchmarks, which adds uncertainty to expectations of running time.To address the issues above, we design FourierSAT, an incomplete SAT solver based on Fourier analysis of Boolean functions, a technique to represent Boolean functions by multilinear polynomials. By such a reduction to continuous optimization, we propose an algebraic framework for solving systems consisting of different types of constraints. The idea is to leverage gradient information to guide the search process in the direction of local improvements. Empirical results demonstrate that FourierSAT is more robust than other solvers on certain classes of benchmarks.

scholarly journals Dampak Pandemi Covid-19 terhadap Kinerja Keuangan Perusahaan Sektor Jasa di BEI

2021 ◽  
Vol 7 (2) ◽  
pp. 227-233
Author(s):  
Maria J F Esomar ◽  
Restia Christianty
Keyword(s):  
Financial Performance ◽  
Hypothesis Testing ◽  
Sampling Method ◽  
Stock Exchange ◽  
Paired Sample ◽  
Empirical Results ◽  
Significant Difference ◽  
Before And After ◽  
The Impact ◽  
Profitability Ratios

The Covid-19 pandemic has caused many hotels, restaurants and tourism activities to be temporarily closed. It has an impact on the financial performance towards the companies engaged in this sub-sector. The objective of this study is to analyze the impact of Covid 19 towards the financial performance of companies engaged in the sub-sector of hotel, restaurant and tourism. Financial performance is measured using several ratios, namely liquidity ratios, solvability ratios, profitability ratios and market ratio. The ype of research is descriptive quantitave. The population in this study is 35 all companies in the sub-sector of hotel, restaurant and tourism listed on the Indonesia Stock Exchange in 2019-2020 period. Samples are collected from 30 companies using purposive sampling method. Hypothesis testing is conducted using the Paired Sample t-Test. The empirical results show that, in the liquidity ratio, and market ratio there is no significant difference between the periods of before and after the first recorded Covid-19 case in Indonesia. Meanwhile, in the solvability ratio and profitability ratio, there are significant differences between the two periods.

scholarly journals Divide and Conquer: Towards Faster Pseudo-Boolean Solving

2018 ◽  
Author(s):  
Jan Elffers ◽  
Jakob Nordström
Keyword(s):  
Boolean Satisfiability ◽  
Conflict Analysis ◽  
Divide And Conquer ◽  
Theoretical Strength ◽  
Integer Coefficient ◽  
Sat Solvers ◽  
Wide Range ◽  
Clause Learning

The last 20 years have seen dramatic improvements in the performance of algorithms for Boolean satisfiability---so-called SAT solvers---and today conflict-driven clause learning (CDCL) solvers are routinely used in a wide range of application areas. One serious short-coming of CDCL, however, is that the underlying method of reasoning is quite weak. A tantalizing solution is to instead use stronger pseudo-Boolean (PB) reasoning, but so far the promise of exponential gains in performance has failed to materialize---the increased theoretical strength seems hard to harness algorithmically, and in many applications CDCL-based methods are still superior. We propose a modified approach to pseudo-Boolean solving based on division instead of the saturation rule used in [Chai and Kuehlmann '05] and other PB solvers. In addition to resulting in a stronger conflict analysis, this also improves performance by keeping integer coefficient sizes down, and yields a very competitive solver as shown by the results in the Pseudo-Boolean Competitions 2015 and 2016.

scholarly journals Reducing SAT to Max2SAT

2021 ◽  
Author(s):  
Carlos Ansótegui ◽  
Jordi Levy
Keyword(s):  
Efficient Method ◽  
Combinatorial Structure ◽  
Constructive Method ◽  
Empirical Results ◽  
Sat Solvers

In the literature, we find reductions from 3SAT to Max2SAT. These reductions are based on the usage of a gadget, i.e., a combinatorial structure that allows translating constraints of one problem to constraints of another. Unfortunately, the generation of these gadgets lacks an intuitive or efficient method. In this paper, we provide an efficient and constructive method for Reducing SAT to Max2SAT and show empirical results of how MaxSAT solvers are more efficient than SAT solvers solving the translation of hard formulas for Resolution.

Enhancing Clause Learning by Symmetry in SAT Solvers

2010 ◽  
Author(s):  
Belaid Benhamou ◽  
Tarek Nabhani ◽  
Richard Ostrowski ◽  
Mohamed Reda Saidi
Keyword(s):  
Sat Solvers ◽  
Clause Learning
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