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improve handling of logical expr optimization/simplification #821

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Feb 13, 2020
Merged

improve handling of logical expr optimization/simplification #821

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a0d4d7c
improve handling of logical expr optimization
hushaohan Feb 13, 2020
2e586b2
remove stale import
hushaohan Feb 13, 2020
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15 changes: 10 additions & 5 deletions qiskit/aqua/components/oracles/logical_expression_oracle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,8 @@
import re

from sympy.parsing.sympy_parser import parse_expr
from sympy.logic.boolalg import to_cnf, BooleanTrue, BooleanFalse
from sympy.logic import simplify_logic
from sympy.logic.boolalg import is_cnf, is_dnf, BooleanTrue, BooleanFalse
from qiskit import QuantumCircuit, QuantumRegister

from qiskit.aqua import AquaError
Expand Down Expand Up @@ -171,14 +172,18 @@ def _process_expr(self):
self._num_vars = len(self._expr.binary_symbols)
self._lit_to_var = [None] + sorted(self._expr.binary_symbols, key=str)
self._var_to_lit = dict(zip(self._lit_to_var[1:], range(1, self._num_vars + 1)))
cnf = to_cnf(self._expr, simplify=self._optimization)

if isinstance(cnf, BooleanTrue):
if self._optimization or (not is_cnf(self._expr) and not is_dnf(self._expr)):
expr = simplify_logic(self._expr)
else:
expr = self._expr

if isinstance(expr, BooleanTrue):
ast = 'const', 1
elif isinstance(cnf, BooleanFalse):
elif isinstance(expr, BooleanFalse):
ast = 'const', 0
else:
ast = get_ast(self._var_to_lit, cnf)
ast = get_ast(self._var_to_lit, expr)

if ast[0] == 'or':
self._nf = DNF(ast, num_vars=self._num_vars)
Expand Down