PicoSAT

PicoSAT is a popular and highly efficient conflict-driven clause learning (CDCL) SAT solver written in pure C. It is known for its small code size, portability, and competitive performance on a wide range of SAT instances.

Overview

PicoSAT was developed by Armin Biere at the Johannes Kepler University Linz. Its design emphasizes simplicity and efficiency, making it suitable for embedded systems and resource-constrained environments. Despite its compact size, PicoSAT implements modern SAT solving techniques such as:

• Conflict-Driven Clause Learning (CDCL): A powerful search algorithm that analyzes conflicts to learn new clauses, pruning the search space.
• Variable Activity Heuristics: Strategies for selecting which variables to branch on during the search process.
• Clause Deletion Strategies: Techniques for removing less useful learned clauses to manage memory consumption and improve performance.
• Restarts: Periodically restarting the search process to escape local minima.
• Two-Watched Literals Scheme: An efficient method for implementing unit propagation.
• Inprocessing: Simplification techniques applied during search to reduce the size of the formula.

Key Features

• Small Code Size: One of the smallest complete SAT solvers, making it easily auditable and integrable.
• Portability: Written in ANSI C, ensuring compatibility across a wide range of platforms.
• Efficiency: Competitive performance on many SAT benchmarks.
• Open Source: Freely available under a permissive license.
• Simplicity: Designed for ease of understanding and modification.

Applications

PicoSAT has found applications in various domains, including:

• Formal Verification: Verifying the correctness of hardware and software systems.
• Artificial Intelligence: Solving planning and reasoning problems.
• Combinatorial Optimization: Finding optimal solutions to constraint satisfaction problems.
• Software Engineering: Bug finding and program analysis.
• Embedded Systems: Verification and validation of embedded software.

Licensing

PicoSAT is typically distributed under the MIT License, allowing for free use, modification, and distribution, even for commercial purposes.

Further Reading

• The official PicoSAT website maintained by Armin Biere (often contains research papers and updated information).