42 lines
1.2 KiB
Python
42 lines
1.2 KiB
Python
from sympy.assumptions.cnf import EncodedCNF
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def pycosat_satisfiable(expr, all_models=False):
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import pycosat
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if not isinstance(expr, EncodedCNF):
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exprs = EncodedCNF()
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exprs.add_prop(expr)
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expr = exprs
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# Return UNSAT when False (encoded as 0) is present in the CNF
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if {0} in expr.data:
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if all_models:
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return (f for f in [False])
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return False
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if not all_models:
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r = pycosat.solve(expr.data)
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result = (r != "UNSAT")
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if not result:
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return result
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return {expr.symbols[abs(lit) - 1]: lit > 0 for lit in r}
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else:
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r = pycosat.itersolve(expr.data)
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result = (r != "UNSAT")
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if not result:
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return result
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# Make solutions SymPy compatible by creating a generator
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def _gen(results):
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satisfiable = False
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try:
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while True:
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sol = next(results)
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yield {expr.symbols[abs(lit) - 1]: lit > 0 for lit in sol}
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satisfiable = True
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except StopIteration:
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if not satisfiable:
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yield False
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return _gen(r)
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