PicoSAT Solver¶
This solver relies on the pycosat Python bindings to PicoSAT.
The pycosat package should be installed on your Sage installation.
AUTHORS:
- Thierry Monteil (2018): initial version. 
- class sage.sat.solvers.picosat.PicoSAT(verbosity=0, prop_limit=0)[source]¶
- Bases: - SatSolver- PicoSAT Solver. - INPUT: - verbosity– integer between 0 and 2 (default: 0)
- prop_limit– integer (default: 0); the propagation limit
 - EXAMPLES: - sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() # optional - pycosat - >>> from sage.all import * >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() # optional - pycosat - add_clause(lits)[source]¶
- Add a new clause to set of clauses. - INPUT: - lits– tuple of nonzero integers
 - Note - If any element - ein- litshas- abs(e)greater than the number of variables generated so far, then new variables are created automatically.- EXAMPLES: - sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() # optional - pycosat sage: solver.add_clause((1, -2 , 3)) # optional - pycosat - >>> from sage.all import * >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() # optional - pycosat >>> solver.add_clause((Integer(1), -Integer(2) , Integer(3))) # optional - pycosat 
 - clauses(filename=None)[source]¶
- Return original clauses. - INPUT: - filename– (optional) if given, clauses are written to- filenamein DIMACS format
 - OUTPUT: - If - filenameis- Nonethen a list of- litsis returned, where- litsis a list of literals.- If - filenamepoints to a writable file, then the list of original clauses is written to that file in DIMACS format.- EXAMPLES: - sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() # optional - pycosat sage: solver.add_clause((1,2,3,4,5,6,7,8,-9)) # optional - pycosat sage: solver.clauses() # optional - pycosat [[1, 2, 3, 4, 5, 6, 7, 8, -9]] - >>> from sage.all import * >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() # optional - pycosat >>> solver.add_clause((Integer(1),Integer(2),Integer(3),Integer(4),Integer(5),Integer(6),Integer(7),Integer(8),-Integer(9))) # optional - pycosat >>> solver.clauses() # optional - pycosat [[1, 2, 3, 4, 5, 6, 7, 8, -9]] - DIMACS format output: - sage: # optional - pycosat sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() sage: solver.add_clause((1, 2, 4)) sage: solver.add_clause((1, 2, -4)) sage: fn = tmp_filename() sage: solver.clauses(fn) sage: print(open(fn).read()) p cnf 4 2 1 2 4 0 1 2 -4 0 - >>> from sage.all import * >>> # optional - pycosat >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() >>> solver.add_clause((Integer(1), Integer(2), Integer(4))) >>> solver.add_clause((Integer(1), Integer(2), -Integer(4))) >>> fn = tmp_filename() >>> solver.clauses(fn) >>> print(open(fn).read()) p cnf 4 2 1 2 4 0 1 2 -4 0 <BLANKLINE> 
 - nvars()[source]¶
- Return the number of variables. - Note that for compatibility with DIMACS convention, the number of variables corresponds to the maximal index of the variables used. - EXAMPLES: - sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() # optional - pycosat sage: solver.nvars() # optional - pycosat 0 - >>> from sage.all import * >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() # optional - pycosat >>> solver.nvars() # optional - pycosat 0 - If a variable with intermediate index is not used, it is still considered as a variable: - sage: solver.add_clause((1,-2,4)) # optional - pycosat sage: solver.nvars() # optional - pycosat 4 - >>> from sage.all import * >>> solver.add_clause((Integer(1),-Integer(2),Integer(4))) # optional - pycosat >>> solver.nvars() # optional - pycosat 4 
 - var(decision=None)[source]¶
- Return a new variable. - INPUT: - decision– ignored; accepted for compatibility with other solvers
 - EXAMPLES: - sage: from sage.sat.solvers.picosat import PicoSAT sage: solver = PicoSAT() # optional - pycosat sage: solver.var() # optional - pycosat 1 sage: solver.add_clause((-1,2,-4)) # optional - pycosat sage: solver.var() # optional - pycosat 5 - >>> from sage.all import * >>> from sage.sat.solvers.picosat import PicoSAT >>> solver = PicoSAT() # optional - pycosat >>> solver.var() # optional - pycosat 1 >>> solver.add_clause((-Integer(1),Integer(2),-Integer(4))) # optional - pycosat >>> solver.var() # optional - pycosat 5