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optimizations, fixes, TODO items

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-09-21 14:50:18 -07:00
parent 444084f396
commit 6478e789e9
6 changed files with 87 additions and 28 deletions
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31
src/math/polysat/ule_constraint.cpp
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@ -12,15 +12,16 @@ Author:
Notes:
TODO: add rewrite rules to simplify expressions
Rewrite rules to simplify expressions
- k1 <= k2 ==> 0 <= 0 if k1 <= k2
- k1 <= k2 ==> 1 <= 0 if k1 > k2
- 0 <= p ==> 0 <= 0
- p <= -1 ==> 0 <= 0
- k*p <= 0 ==> p <= 0 if k is odd
- k*2^n*p <= 0 ==> 2^n*p <= 0 if k is odd, leading coeffient is always a power of 2.
- k <= p ==> p - k <= - k - 1
- k <= p ==> p - k <= k - 1
TODO:
- p <= p + q ==> p <= -q - 1
- p + k <= p ==> p + k <= k - 1 for k > 0
@ -45,11 +46,35 @@ namespace polysat {
}
void ule_constraint::simplify() {
if (m_lhs.is_zero()) {
m_rhs = 0;
return;
}
if (m_rhs.is_val() && m_rhs.val() == m_rhs.manager().max_value()) {
m_lhs = 0, m_rhs = 0;
return;
}
if (m_lhs.is_val() && m_rhs.is_val()) {
if (m_lhs.val() <= m_rhs.val())
m_lhs = m_rhs = 0;
else
m_lhs = 1, m_rhs = 0;
return;
}
// k <= p => p - k <= - k - 1
if (m_lhs.is_val()) {
pdd k = m_lhs;
m_lhs = m_rhs - k;
m_rhs = - k - 1;
}
// normalize leading coefficient to be a power of 2
if (m_rhs.is_zero() && !m_lhs.leading_coefficient().is_power_of_two()) {
rational lc = m_lhs.leading_coefficient();
rational x, y;
gcd(lc, m_lhs.manager().two_to_N(), x, y);
if (x.is_neg())
x = mod(x, m_lhs.manager().two_to_N());
m_lhs *= x;
}
}