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Forward propagation for op_constraints + optimization for left/right shift

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This commit is contained in:
Clemens Eisenhofer 2023-01-11 10:29:26 +01:00
parent 1d0ad1ccc0
commit 2581754c3e
4 changed files with 89 additions and 45 deletions
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74
src/math/polysat/op_constraint.cpp
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@ -229,10 +229,11 @@ namespace polysat {
* when r, q are variables.
*/
clause_ref op_constraint::lemma_lshr(solver& s, assignment const& a) {
auto& m = p().manager();
auto const pv = a.apply_to(p());
auto const qv = a.apply_to(q());
auto const rv = a.apply_to(r());
unsigned const K = p().manager().power_of_2();
unsigned const K = m.power_of_2();
signed_constraint const lshr(this, true);
@ -253,7 +254,7 @@ namespace polysat {
// q >= k -> r <= 2^{K-k} - 1
return s.mk_clause(~lshr, ~s.ule(qv.val(), q()), s.ule(r(), rational::power_of_two(K - qv.val().get_unsigned()) - 1), true);
else if (pv.is_val() && rv.is_val() && qv.is_val() && !qv.is_zero()) {
unsigned const k = qv.val().get_unsigned();
unsigned k = qv.val().get_unsigned();
// q = k -> r[i] = p[i+k] for 0 <= i < K - k
for (unsigned i = 0; i < K - k; ++i) {
if (rv.val().get_bit(i) && !pv.val().get_bit(i + k)) {
@ -265,7 +266,18 @@ namespace polysat {
}
}
else {
// forward propagation
SASSERT(!(pv.is_val() && qv.is_val() && rv.is_val()));
if (qv.is_val() && !rv.is_val()) {
const rational& qr = qv.val();
if (qr >= m.power_of_2())
return s.mk_clause(~lshr, ~s.ule(m.mk_val(m.power_of_2()), q()), s.eq(r()), true);
if (rv.is_val()) {
const rational& pr = pv.val();
return s.mk_clause(~lshr, ~s.eq(p(), m.mk_val(pr)), ~s.eq(q(), m.mk_val(qr)), s.eq(r(), m.mk_val(machine_div(pr, rational::power_of_two(qr.get_unsigned())))), true);
}
}
}
return {};
}
@ -309,10 +321,11 @@ namespace polysat {
* q = 0 -> r = p
*/
clause_ref op_constraint::lemma_shl(solver& s, assignment const& a) {
auto& m = p().manager();
auto const pv = a.apply_to(p());
auto const qv = a.apply_to(q());
auto const rv = a.apply_to(r());
unsigned const K = p().manager().power_of_2();
unsigned const K = m.power_of_2();
signed_constraint const shl(this, true);
@ -333,7 +346,7 @@ namespace polysat {
// q >= k -> r - 1 >= 2^k - 1 (equivalent unit constraint to better support narrowing)
return s.mk_clause(~shl, ~s.ule(qv.val(), q()), s.ule(rational::power_of_two(qv.val().get_unsigned()) - 1, r() - 1), true);
else if (pv.is_val() && rv.is_val() && qv.is_val() && !qv.is_zero()) {
unsigned const k = qv.val().get_unsigned();
unsigned k = qv.val().get_unsigned();
// q = k -> r[i+k] = p[i] for 0 <= i < K - k
for (unsigned i = 0; i < K - k; ++i) {
if (rv.val().get_bit(i + k) && !pv.val().get_bit(i)) {
@ -345,7 +358,18 @@ namespace polysat {
}
}
else {
// forward propagation
SASSERT(!(pv.is_val() && qv.is_val() && rv.is_val()));
if (qv.is_val() && !rv.is_val()) {
const rational& qr = qv.val();
if (qr >= m.power_of_2())
return s.mk_clause(~shl, ~s.ule(m.mk_val(m.power_of_2()), q()), s.eq(r()), true);
if (rv.is_val()) {
const rational& pr = pv.val();
return s.mk_clause(~shl, ~s.eq(p(), m.mk_val(pr)), ~s.eq(q(), m.mk_val(qr)), s.eq(r(), m.mk_val(rational::power_of_two(qr.get_unsigned()) * pr)), true);
}
}
}
return {};
}
@ -525,6 +549,12 @@ namespace polysat {
return s.mk_clause(~andc, s.ule(r(), p()), true);
if (qv.is_zero() && !rv.is_zero()) // rv not necessarily fully evaluated
return s.mk_clause(~andc, s.ule(r(), q()), true);
if (pv.is_val() && qv.is_val() && !rv.is_val()) {
const rational& pr = pv.val();
const rational& qr = qv.val();
return s.mk_clause(~s.eq(p(), m.mk_val(pr)), ~s.eq(q(), m.mk_val(qr)), s.eq(r(), m.mk_val(bitwise_and(pr, qr))), true);
}
return {};
}
@ -596,27 +626,39 @@ namespace polysat {
auto& m = p().manager();
auto pv = a.apply_to(p());
auto rv = a.apply_to(r());
if (!pv.is_val() || !rv.is_val() || eval_inv(pv, rv) == l_true)
if (eval_inv(pv, rv) == l_true)
return {};
unsigned parity_pv = pv.val().trailing_zeros();
unsigned parity_rv = rv.val().trailing_zeros();
signed_constraint const invc(this, true);
// p = 0 => r = 0
if (pv.is_zero())
return s.mk_clause(~invc, ~s.eq(p()), s.eq(r()), true);
// r = 0 => p = 0
if (rv.is_zero())
return s.mk_clause(~invc, ~s.eq(r()), s.eq(p()), true);
// p assigned => r = pseudo_inverse(eval(p))
if (pv.is_val() && !rv.is_val()) {
verbose_stream() << "Inverse ---+++ \n";
verbose_stream() << "Inverse of " << s.eq(p(), pv) << " = " << s.eq(r(), pv.val().pseudo_inverse(m.power_of_2())) << "\n";
return s.mk_clause(~invc, ~s.eq(p(), pv), s.eq(r(), pv.val().pseudo_inverse(m.power_of_2())), true);
}
if (!pv.is_val() || !rv.is_val())
return {};
unsigned parity_pv = pv.val().trailing_zeros();
unsigned parity_rv = rv.val().trailing_zeros();
// odd(r)
if (parity_rv != 0)
return s.mk_clause(~invc, s.odd(r()), true);
// parity(p) >= k && p * r < 2^k => p * r >= 2^k
// parity(p) < k && p * r >= 2^k => p * r < 2^k
rational prod = (p() * r()).val();
pdd prod = p() * r();
rational prodv = (pv * rv).val();
SASSERT(prod != rational::power_of_two(parity_pv)); // Why did it evaluate to false in this case?
unsigned lower = 0, upper = p().power_of_2();
// binary search for the parity
@ -626,14 +668,14 @@ namespace polysat {
if (parity_pv >= middle) {
lower = middle;
LOG("Its in [" << lower << "; " << upper << ")");
if (prod < rational::power_of_two(middle))
return s.mk_clause(~invc, ~s.parity_at_least(p(), middle), s.uge(p() * r(), rational::power_of_two(middle)), false);
if (prodv < rational::power_of_two(middle))
return s.mk_clause(~invc, ~s.parity_at_least(p(), middle), s.uge(prod, rational::power_of_two(middle)), false);
}
else {
upper = middle;
LOG("Its in [" << lower << "; " << upper << ")");
if (prod >= rational::power_of_two(middle))
return s.mk_clause(~invc, s.parity_at_least(p(), middle), s.ult(p() * r(), rational::power_of_two(middle)), false);
if (prodv >= rational::power_of_two(middle))
return s.mk_clause(~invc, s.parity_at_least(p(), middle), s.ult(prod, rational::power_of_two(middle)), false);
}
}
UNREACHABLE();