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fix #9030: box mode objectives are now optimized independently

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In box mode (opt.priority=box), each objective should be optimized
independently. Previously, box() called geometric_opt() which optimizes
all objectives together using a shared disjunction of bounds. This caused
adding/removing an objective to change the optimal values of other
objectives.

Fix: Rewrite box() to optimize each objective in its own push/pop scope
using geometric_lex, ensuring complete isolation between objectives.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Lev Nachmanson 2026-03-19 10:09:34 -10:00 • committed by Lev Nachmanson
parent e351266ecb
commit acd2e9475d
4 changed files with 101 additions and 15 deletions
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40
src/opt/optsmt.cpp
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@ -202,15 +202,19 @@ namespace opt {
}
}
lbool optsmt::geometric_lex(unsigned obj_index, bool is_maximize) {
lbool optsmt::geometric_lex(unsigned obj_index, bool is_maximize, bool is_box) {
TRACE(opt, tout << "index: " << obj_index << " is-max: " << is_maximize << "\n";);
arith_util arith(m);
bool is_int = arith.is_int(m_objs.get(obj_index));
lbool is_sat = l_true;
expr_ref bound(m), last_bound(m);
for (unsigned i = 0; i < obj_index; ++i)
commit_assignment(i);
// In lex mode, commit previous objectives so that earlier objectives
// constrain later ones. In box mode, skip this so each objective
// is optimized independently.
if (!is_box)
for (unsigned i = 0; i < obj_index; ++i)
commit_assignment(i);
unsigned steps = 0;
unsigned step_incs = 0;
@ -291,9 +295,9 @@ namespace opt {
// set the solution tight.
m_upper[obj_index] = m_lower[obj_index];
for (unsigned i = obj_index+1; i < m_lower.size(); ++i) {
m_lower[i] = inf_eps(rational(-1), inf_rational(0));
}
if (!is_box)
for (unsigned i = obj_index+1; i < m_lower.size(); ++i)
m_lower[i] = inf_eps(rational(-1), inf_rational(0));
return l_true;
}
@ -534,15 +538,23 @@ namespace opt {
if (m_vars.empty()) {
return is_sat;
}
// assertions added during search are temporary.
solver::scoped_push _push(*m_s);
if (m_optsmt_engine == symbol("symba")) {
is_sat = symba_opt();
// In box mode, optimize each objective independently.
// Each objective gets its own push/pop scope so that bounds
// from one objective do not constrain another.
// Note: geometric_lex is used unconditionally here, even when
// m_optsmt_engine is "symba", because symba_opt and geometric_opt
// optimize all objectives jointly, violating box mode semantics.
m_context.get_base_model(m_best_model);
for (unsigned i = 0; i < m_vars.size() && m.inc(); ++i) {
solver::scoped_push _push(*m_s);
is_sat = geometric_lex(i, true, true);
if (is_sat == l_undef)
return l_undef;
if (is_sat == l_false)
return l_false;
m_models.set(i, m_best_model.get());
}
else {
is_sat = geometric_opt();
}
return is_sat;
return l_true;
}