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Fix the in-place negation of Xor in the TseitinEncoder #68

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merged 1 commit into from
Aug 19, 2024
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Fix the in-place negation of Xor in the TseitinEncoder #68

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53 changes: 51 additions & 2 deletions crates/pindakaas/src/propositional_logic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -261,7 +261,13 @@ impl<DB: ClauseDatabase> Encoder<DB, Formula> for TseitinEncoder {
let neg_els: Formula = !*els.clone();
self.encode(&mut cdb, &neg_els)
}
Formula::Xor(sub) => {
Formula::Equiv(sub) if sub.len() == 2 => {
self.encode(db, &Formula::Xor(sub.clone()))
}
Formula::Xor(sub) if sub.len() == 2 => {
self.encode(db, &Formula::Equiv(sub.clone()))
}
Formula::Xor(sub) if sub.len() % 2 != 0 => {
let neg_sub = sub.iter().map(|f| !(f.clone())).collect();
self.encode(db, &Formula::Xor(neg_sub))
}
Expand Down Expand Up @@ -339,7 +345,7 @@ impl<DB: ClauseDatabase> Encoder<DB, Formula> for TseitinEncoder {
#[cfg(test)]
mod tests {
use crate::{
helpers::tests::{assert_enc_sol, lits},
helpers::tests::{assert_enc_sol, assert_sol, lits},
Encoder, Formula, Lit, TseitinEncoder,
};

Expand Down Expand Up @@ -507,6 +513,49 @@ mod tests {
=> vec![lits![-1, -3, -5], lits![1, 3, -5], lits![-1, 3, 5], lits![1, -3, 5], lits![-2, -4, -5], lits![2, -4, 5], lits![2, 4, -5], lits![-2, 4, 5]],
vec![lits![-1, -2, -3, -4], lits![-1, -2, 3, 4], lits![-1, 2, -3, 4], lits![-1, 2, 3, -4], lits![1, -2, -3, 4], lits![1, -2, 3, -4], lits![1, 2, -3, -4], lits![1, 2, 3, 4]]
);
// Regression test: negated XOR (into equiv)
assert_enc_sol!(
TseitinEncoder,
2,
&Formula::Not(Box::new(Formula::Xor(vec![
Formula::Atom(1.into()),
Formula::Atom(2.into()),
])))
=> vec![lits![-1, 2,], lits![1,-2]],
vec![lits![-1, -2],lits![1, 2]]
);
// Regression test: negated XOR (negated args)
assert_sol!(
TseitinEncoder,
3,
&Formula::Not(Box::new(Formula::Xor(vec![
Formula::Atom(1.into()),
Formula::Atom(2.into()),
Formula::Atom(3.into()),
])))
=> vec![lits![-1, -2, -3], lits![1, 2, -3], lits![-1, 2, 3], lits![1, -2, 3]]
);
// Regression test: negated XOR (negated binding)
assert_sol!(
TseitinEncoder,
4,
&Formula::Not(Box::new(Formula::Xor(vec![
Formula::Atom(1.into()),
Formula::Atom(2.into()),
Formula::Atom(3.into()),
Formula::Atom(4.into()),
])))
=> vec![
lits![-1, -2, -3, -4],
lits![1, 2, -3, -4],
lits![1, -2, 3, -4],
lits![1, -2, -3, 4],
lits![-1, 2, 3, -4],
lits![-1, 2, -3, 4],
lits![-1, -2, 3, 4],
lits![1, 2, 3, 4]
]
);
}

#[test]
Expand Down
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