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nra_solver: parameterize falsified-literal selection in check_assignment

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Add smt.arith.nl.nra_check_assignment_pick (UINT, default 0) to
choose between two strategies for picking the single falsified
constraint that is sent to NLSAT in check_assignment():

  0 - minimal substitution-expansion size in the max variable
      (cheap LRA-side proxy for the lowest-degree-in-max-var
      heuristic of nlsat::solver::check(rvalues, clause); default).
  1 - uniformly random falsified constraint.

The selection is performed entirely on the LRA side; only the
chosen constraint is materialized as an NLSAT polynomial.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Lev Nachmanson 2026-05-21 15:11:43 -07:00
parent 923e29c9c8
commit ec72144c66
2 changed files with 20 additions and 9 deletions
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28
src/math/lp/nra_solver.cpp
View file

@ -433,16 +433,26 @@ struct solver::imp {
if (falsified.empty())
return l_undef;
// Pick the falsified constraint with the smallest substitution
// expansion as a cheap LRA-side proxy for the lowest-degree
// heuristic that nlsat_solver::check(rvalues, clause) would apply.
// Pick the falsified constraint according to
// arith.nl.nra_check_assignment_pick:
// 0 - minimal substitution expansion (cheap LRA-side proxy
// for the lowest-degree-in-max-var heuristic that
// nlsat::solver::check(rvalues, clause) applies).
// 1 - uniformly random falsified constraint.
lp::constraint_index best = falsified[0];
unsigned best_score = constraint_expansion_size(best);
for (unsigned k = 1; k < falsified.size(); ++k) {
unsigned sc = constraint_expansion_size(falsified[k]);
if (sc < best_score) {
best_score = sc;
best = falsified[k];
unsigned pick_mode = m_nla_core.params().arith_nl_nra_check_assignment_pick();
if (pick_mode == 1) {
unsigned k = m_nla_core.random() % falsified.size();
best = falsified[k];
}
else {
unsigned best_score = constraint_expansion_size(best);
for (unsigned k = 1; k < falsified.size(); ++k) {
unsigned sc = constraint_expansion_size(falsified[k]);
if (sc < best_score) {
best_score = sc;
best = falsified[k];
}
}
}

1
src/params/smt_params_helper.pyg
View file

@ -63,6 +63,7 @@ def_module_params(module_name='smt',
('arith.nl.nra', BOOL, True, 'call nra_solver when incremental linearization does not produce a lemma, this option is ignored when arith.nl=false, relevant only if smt.arith.solver=6'),
('arith.nl.nra_check_assignment', BOOL, True, 'call check_assignment in nra_solver to verify current assignment against nlsat constraints'),
('arith.nl.nra_check_assignment_max_fail', UINT, 7, 'maximum consecutive check_assignment failures before disabling it'),
('arith.nl.nra_check_assignment_pick', UINT, 0, 'falsified-literal selection in check_assignment: 0 - minimal degree (size) of the max variable (default), 1 - random'),
('arith.nl.branching', BOOL, True, 'branching on integer variables in non linear clusters'),
('arith.nl.expensive_patching', BOOL, False, 'use the expensive of monomials'),
('arith.nl.rounds', UINT, 1024, 'threshold for number of (nested) final checks for non linear arithmetic, relevant only if smt.arith.solver=2'),