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optimizations by using cached psc

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2025-12-17 15:34:05 -10:00
parent c37adafe12
commit 0c0142d6bb
1 changed files with 86 additions and 13 deletions
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99
src/nlsat/levelwise.cpp
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@ -173,10 +173,11 @@ namespace nlsat {
assignment & sample() { return m_solver.sample(); }
polynomial::cache & m_cache;
todo_set m_unique_set;
polynomial_ref_vector m_psc_tmp;
// max_x plays the role of n in algorith 1 of the levelwise paper.
impl(solver& solver, polynomial_ref_vector const& ps, var max_x, assignment const& s, pmanager& pm, anum_manager& am, polynomial::cache & cache)
: m_solver(solver), m_P(ps), m_n(max_x), m_pm(pm), m_am(am), m_cache(cache), m_unique_set(cache, true) {
: m_solver(solver), m_P(ps), m_n(max_x), m_pm(pm), m_am(am), m_cache(cache), m_unique_set(cache, true), m_psc_tmp(m_pm) {
TRACE(lws, tout << "m_n:" << m_n << "\n";);
m_I.reserve(m_n); // cannot just resize bcs of the absence of the default constructor of root_function_interval
for (unsigned i = 0; i < m_n; ++i)
@ -191,6 +192,54 @@ namespace nlsat {
unsigned max_var(poly* p) { return m_pm.max_var(p); }
unsigned max_var(polynomial_ref const & p) { return m_pm.max_var(p); }
// Wrapper to use cached PSC chain computation
void psc_chain(polynomial_ref & p, polynomial_ref & q, unsigned x, polynomial_ref_vector & result) {
m_cache.psc_chain(p, q, x, result);
}
// Use the PSC chain of p and its derivative w.r.t x to obtain a discriminant candidate.
// Prefer the first non-constant PSC; fall back to zero/constant if nothing else appears,
// and finally to the classic discriminant if the chain is empty.
polynomial_ref psc_discriminant(polynomial_ref const & p_in, unsigned x) {
polynomial_ref p(p_in);
polynomial_ref d(m_pm);
d = derivative(p, x);
polynomial_ref_vector & chain = m_psc_tmp;
chain.reset();
psc_chain(p, d, x, chain);
polynomial_ref disc(m_pm);
polynomial_ref last_const(m_pm);
bool saw_zero = false;
for (unsigned i = 0; i < chain.size(); ++i) {
polynomial_ref s(chain.get(i), m_pm);
if (is_zero(s)) {
saw_zero = true;
continue;
}
if (is_const(s)) {
if (!last_const)
last_const = s;
continue;
}
disc = s;
break;
}
if (disc)
return disc;
if (saw_zero)
disc = m_pm.mk_zero();
if (last_const)
return last_const;
// Fallback to the classic discriminant if PSC chain did not yield anything usable.
disc = discriminant(p, x);
return disc;
}
// Helper to print out m_Q
std::ostream& display(std::ostream& out) {
out << "{\n";
@ -520,14 +569,34 @@ namespace nlsat {
polynomial_ref pa(a, m_pm);
polynomial_ref pb(b, m_pm);
polynomial_ref r(m_pm);
r = resultant(pa, pb, x);
TRACE(lws,
tout << "resultant wrt x" << x << "\n";
::nlsat::display(tout << "a: ", m_solver, pa) << "\n";
::nlsat::display(tout << "b: ", m_solver, pb) << "\n";
::nlsat::display(tout << "r: ", m_solver, r) << "\n";);
if (is_zero(r)) {
TRACE(lws, tout << "zero resultant\n";);
polynomial_ref_vector & chain = m_psc_tmp;
chain.reset();
psc_chain(pa, pb, x, chain);
polynomial_ref candidate(m_pm);
bool has_zero = false;
for (unsigned i = 0; i < chain.size(); ++i) {
polynomial_ref s(chain.get(i), m_pm);
if (is_zero(s)) {
has_zero = true;
continue;
}
if (is_const(s))
continue;
candidate = s;
break;
}
if (candidate) {
r = candidate;
TRACE(lws,
tout << "psc resultant wrt x" << x << "\n";
::nlsat::display(tout << "a: ", m_solver, pa) << "\n";
::nlsat::display(tout << "b: ", m_solver, pb) << "\n";
::nlsat::display(tout << "r: ", m_solver, r) << "\n";);
}
else if (has_zero) {
TRACE(lws, tout << "psc resultant is zero\n";);
polynomial_ref g(m_pm);
m_pm.gcd(a, b, g);
SASSERT (!is_const(g));
@ -575,6 +644,10 @@ namespace nlsat {
});
return;
}
else {
TRACE(lws, tout << "psc resultant is constant; skipping ord_inv\n";);
return;
}
for_each_distinct_factor(r, [&](polynomial_ref& f) {
TRACE(lws, tout << "f:" << f << "\n";);
mk_prop(prop_enum::ord_inv, f);
@ -618,7 +691,7 @@ namespace nlsat {
// handle ord_inv(discriminant_{x_{i+1}}(p)) for an_del pre-processing
void add_ord_inv_discriminant_for(const property& p) {
polynomial::polynomial_ref disc(m_pm);
disc = discriminant(p.m_poly, max_var(p.m_poly));
disc = psc_discriminant(p.m_poly, max_var(p.m_poly));
TRACE(lws, display(tout << "p:", p) << "\n"; ::nlsat::display(tout << "discriminant by x" << max_var(p.m_poly)<< ": ", m_solver, disc) << "\n";);
if (!is_const(disc)) {
for_each_distinct_factor(disc, [&](polynomial::polynomial_ref f) {
@ -691,7 +764,7 @@ namespace nlsat {
}
// If a polynomial has a coefficient which is non-zero constant then non_null holds
bool has_non_null_cost_coeff(const polynomial_ref& p) {
bool has_const_coeff(const polynomial_ref& p) {
unsigned level = max_var(p);
unsigned deg = m_pm.degree(p, level);
for (unsigned j = 0; j <= deg; ++j) {
@ -706,7 +779,7 @@ namespace nlsat {
void apply_pre_non_null(const property& p) {
TRACE(lws, tout << "p:"; display(tout, p) << std::endl;);
if (has_non_null_cost_coeff(p.m_poly))
if (has_const_coeff(p.m_poly))
return;
if (!try_non_null_via_coeffs(p))
fail();
@ -755,7 +828,7 @@ namespace nlsat {
}
// compute discriminant w.r.t. the variable at p.level
polynomial_ref disc(m_pm);
disc = discriminant(p.m_poly, level);
disc = psc_discriminant(p.m_poly, level);
SASSERT (!is_zero(disc)); // p.m_poly is supposed to be square free
TRACE(lws, ::nlsat::display(tout << "discriminant: ", m_solver, disc) << "\n";);