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Added justifications for intermediate values [e.g., 2 * x in the pdd (2 * x) + y]

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This might allow propagation in both directions
This commit is contained in:
Clemens Eisenhofer 2022-12-21 13:52:27 +01:00
parent ec06027515
commit c8b9127028
6 changed files with 475 additions and 172 deletions
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56
src/math/polysat/op_constraint.cpp
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@ -277,6 +277,12 @@ namespace polysat {
return l_undef;
}
bool op_constraint::propagate_bits_lshr(solver& s, bool is_positive) {
// TODO: Implement: copy from the left shift
// TODO: Implement: negative case
return true;
}
/**
* Enforce axioms for constraint: r == p << q
*
@ -353,9 +359,10 @@ namespace polysat {
}
bool op_constraint::propagate_bits_shl(solver& s, bool is_positive) {
tbv_ref p_val = s.m_fixed_bits.eval(m_p);
tbv_ref q_val = s.m_fixed_bits.eval(m_q);
tbv_ref r_val = s.m_fixed_bits.eval(m_r);
// TODO: Implement: negative case
tbv_ref& p_val = s.m_fixed_bits.eval(s, m_p);
tbv_ref& q_val = s.m_fixed_bits.eval(s, m_q);
tbv_ref& r_val = s.m_fixed_bits.eval(s, m_r);
unsigned sz = m_p.power_of_2();
auto [shift_min, shift_max] = s.m_fixed_bits.min_max(q_val);
@ -374,15 +381,34 @@ namespace polysat {
SASSERT(shift_max_u <= sz);
SASSERT(shift_min_u <= shift_max_u);
unsigned span = shift_max_u - shift_min_u;
for (unsigned i = 0; i < shift_min_u; i++) {
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_0, this, s.))
return false;
// Shift by at the value we know q to be at least
// TODO: Improve performance; we can reuse the justifications from the previous iteration
if (shift_min_u > 0) {
for (unsigned i = 0; i < shift_min_u; i++) {
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_0, bit_justication_constraint::mk_justify_at_least(this, m_q, q_val, rational(i + 1))))
return false;
}
}
for (unsigned i = shift_min_u; i < sz; i++) {
propagate_bit(s, m_r.var(), i, p_val[i - shift_min_u]);
unsigned j = 0;
tbit val = p_val[i - shift_min_u];
if (val == BIT_z)
continue;
for (; j < span; j++) {
if (p_val[i - shift_min_u + 1] != val)
break;
}
if (j == span) { // all elements we could shift there are equal. We can safely set this value
// TODO: Relax. Sometimes we can reduce the span if further elements in q are set to the respective value
if (!s.m_fixed_bits.fix_value(s, m_r, i, val, bit_justication_constraint::mk_justify_between(this, m_q, q_val, shift_min, shift_max)))
return false;
}
}
return true;
}
void op_constraint::activate_and(solver& s) {
@ -499,12 +525,13 @@ namespace polysat {
}
bool op_constraint::propagate_bits_and(solver& s, bool is_positive){
tbv_ref p_val = s.m_fixed_bits.eval(m_p);
tbv_ref q_val = s.m_fixed_bits.eval(m_q);
tbv_ref r_val = s.m_fixed_bits.eval(m_r);
// TODO: Implement: negative case
tbv_ref& p_val = s.m_fixed_bits.eval(s, m_p);
tbv_ref& q_val = s.m_fixed_bits.eval(s, m_q);
tbv_ref& r_val = s.m_fixed_bits.eval(s, m_r);
unsigned sz = m_p.power_of_2();
for (int i = 0; i < sz; i++) {
for (unsigned i = 0; i < sz; i++) {
tbit bp = p_val[i];
tbit bq = q_val[i];
tbit br = r_val[i];
@ -512,11 +539,12 @@ namespace polysat {
// TODO: Propagate from the result to the operands. e.g., 110... = xx1... & yyy...
// TODO: ==> x = 111..., y = 110...
if (bp == BIT_0 || bq == BIT_0) {
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_0, this, std::pair(m_p, i), std::pair(m_q, i)))
// TODO: In case both are 0 use the one with the lower decision-level and not necessarily p
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_0, bit_justication_constraint::mk_unary(this, { bp == BIT_0 ? m_p : m_q, i })))
return false;
}
else if (bp == BIT_1 && bq == BIT_1) {
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_1, this, std::pair(m_p, i), std::pair(m_q, i)))
if (!s.m_fixed_bits.fix_value(s, m_r, i, BIT_1, bit_justication_constraint::mk_binary(this, { m_p, i }, { m_q, i })))
return false;
}
}