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Fix NLA optimization regression and relax restore_x

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- Relax restore_x() to handle backup/current size mismatches: when
  backup is shorter (new columns added), call
  move_non_basic_columns_to_bounds() to find a feasible solution.
- Fix 100x performance regression in nonlinear optimization: save LP
  optimum before check_nla and return it as bound regardless of NLA
  result, so opt_solver::check_bound() can validate via full re-solve
  with accumulated NLA lemmas.
- Refactor theory_lra::maximize() into three helpers: max_with_lp(),
  max_with_nl(), and max_result().
- Add mk_gt(theory_var, impq const&) overload for building blockers
  from saved LP optimum values.
- Add BNH multi-objective optimization test (7/7 sat in <1s vs 1/7
  in 30s before fix).
- Add restore_x test for backup size mismatch handling.

Fixes #8890

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Lev Nachmanson 2026-03-10 16:38:08 -10:00
parent bb11a56a67
commit 6d890fb026
8 changed files with 357 additions and 61 deletions
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21
src/math/lp/lar_solver.h
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@ -72,7 +72,6 @@ class lar_solver : public column_namer {
void clear_columns_with_changed_bounds();
struct scoped_backup;
public:
const indexed_uint_set& columns_with_changed_bounds() const;
void insert_to_columns_with_changed_bounds(unsigned j);
@ -437,7 +436,25 @@ public:
statistics& stats();
void backup_x() { get_core_solver().backup_x(); }
void restore_x() { get_core_solver().restore_x(); }
void restore_x() {
auto& cs = get_core_solver();
unsigned backup_sz = cs.backup_x_size();
unsigned current_sz = cs.m_n();
CTRACE(lar_solver_restore, backup_sz != current_sz,
tout << "restore_x: backup_sz=" << backup_sz
<< " current_sz=" << current_sz << "\n";);
cs.restore_x();
if (backup_sz < current_sz) {
// New columns were added after backup.
// move_non_basic_columns_to_bounds snaps non-basic
// columns to their bounds and finds a feasible solution.
move_non_basic_columns_to_bounds();
}
else {
SASSERT(ax_is_correct());
SASSERT(cs.m_r_solver.calc_current_x_is_feasible_include_non_basis());
}
}
void updt_params(params_ref const& p);
column_type get_column_type(unsigned j) const { return get_core_solver().m_column_types()[j]; }