jix / kissat_extras

A fork of the Kissat SAT solver with additional features. Supports incremental solving.

The Kissat Extras SAT Solver

This is a fork of Armin Biere's Kissat SAT Solver (arminbiere/kissat). Kassat Extras aims to provide additional functionality currently not available in the upstream version of Kissat.

Warning: This is a work in progress and has not seen sufficient testing for production use.

New Functionality

• Solving under assumptions
  • Requires use of the incremental solving modes mentioned below
• Incremental solving via clause restoration
  • Enabled via the option incremental (on by default)
  • Transparent to the user
• Incremental solving using protect/unprotect
  • Similar to freeze/meld but more flexible w.r.t. inprocessing
  • Allows protecting variables before the first search and fresh variables between searches.
  • Allows assuming and adding new clauses on protected variables even when incremental is off.
  • Still allows equivalent literal substitution of protected variables
  • Planned: allow temporary elimination during inprocessing
  • Planned: user provided constraint propagators on protected variables
• compile_commands.json generation from ./configure

Software that wants to be compatible with both, upstream Kissat and Kissat Extras, can use the KISSAT_EXTRAS preprocessor macro that is defined by this fork.

Why a Fork?

Currently, the upstream project does not accept external contributions. This makes a fork the only option.

Source Code Formatting

Note that I reformatted all source files before I added any new functionality. While I usually try to follow existing conventions when working on an existing project, I make an exception for the GNU code style used by the upstream project.

Besides reformatting, I also adjusted the make indent target to use astyle instead of GNU indent. If it becomes necessary, it should be possible to mostly automate conversion of individual patches from one style to another.

Original Readme

Kissat is a "keep it simple and clean bare metal SAT solver" written in C. It is a port of CaDiCaL back to C with improved data structures, better scheduling of inprocessing and optimized algorithms and implementation.

Coincidentally "kissat" also means "cats" in Finnish.

Run ./configure && make test to configure, build and test in build.