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nseq: port ZIPT regex pre-check to fix benchmark discrepancy on regex-only problems (#8994)

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* Initial plan

* Port ZIPT regex pre-check and DFS node budget to address nseq benchmark discrepancy

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
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Copilot 2026-03-15 10:10:53 -07:00 • committed by GitHub
parent 2212f59704
commit d53846d501
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4
src/smt/seq/seq_nielsen.cpp
View file

@ -2172,6 +2172,10 @@ namespace seq {
if (m_cancel_fn && m_cancel_fn())
return search_result::unknown;
// check DFS node budget (0 = unlimited)
if (m_max_nodes > 0 && m_stats.m_num_dfs_nodes > m_max_nodes)
return search_result::unknown;
// revisit detection: if already visited this run, return cached status.
// mirrors ZIPT's NielsenNode.GraphExpansion() evalIdx check.
if (node->eval_idx() == m_run_idx) {

4
src/smt/seq/seq_nielsen.h
View file

@ -734,6 +734,7 @@ namespace seq {
unsigned m_run_idx = 0;
unsigned m_depth_bound = 0;
unsigned m_max_search_depth = 0;
unsigned m_max_nodes = 0; // 0 = unlimited
bool m_parikh_enabled = true;
unsigned m_next_mem_id = 0;
unsigned m_fresh_cnt = 0;
@ -821,6 +822,9 @@ namespace seq {
// maximum overall search depth (0 = unlimited)
void set_max_search_depth(unsigned d) { m_max_search_depth = d; }
// maximum total DFS nodes per solve() call (0 = unlimited)
void set_max_nodes(unsigned n) { m_max_nodes = n; }
// enable/disable Parikh image verification constraints
void set_parikh_enabled(bool e) { m_parikh_enabled = e; }

6
src/smt/seq/seq_regex.cpp
View file

@ -438,6 +438,12 @@ namespace seq {
// Only handle ground regexes; non-ground can't be fully explored
if (!re->is_ground())
return l_undef;
// s_other snodes (unrecognized regex kinds, e.g. re.+) cannot be
// efficiently explored: the alphabet partition is trivially {∅} and
// derivative computations may be slow. Report l_undef and let the
// caller fall back to a more capable procedure.
if (re->kind() == euf::snode_kind::s_other)
return l_undef;
// BFS over the Brzozowski derivative automaton.
// Each state is a derivative regex snode identified by its id.