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seq_split: add behaviour-neutral perf counters, surfaced via nseq -st

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Adds a split_stats struct to seq_split (make/sigma-expand/materialize/splits/pushes/oracle-prunes/intersect/intersect-pairs/complement/giveups/threshold-overruns/max-split-set/simplify) and reports them in nielsen_graph::collect_statistics as 'nseq split *'. Read-only counters; solver behaviour is unchanged (verified: L11 sat, L14 unsat, gen cssfunc sat). Diagnosis on gen-lb L15 negcount: the De Morgan complement -> intersect cross-product blows up to 2^16 split-set pairs (1.3M intersect-pairs) while simplify() and the oracle never fire on that path.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Margus Veanes 2026-07-03 16:05:31 +03:00
parent 7cc5a73bd8
commit 8992d5fc53
4 changed files with 69 additions and 3 deletions
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24
src/ast/rewriter/seq_split.h
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@ -57,6 +57,25 @@ enum class split_mode { weak, strong };
// default) keeps everything, so sigma is unchanged. See seq_split::compute.
typedef std::function<bool(expr* D, expr* N)> split_oracle;
// Lightweight performance counters for the split algebra (surfaced via -st in
// the nseq solver; behaviour-neutral). See seq_split.cpp for where each fires.
struct split_stats {
unsigned m_make = 0; // make(): suspended sigma(r) built
unsigned m_sigma_expand = 0; // expand_fromre(): one sigma rule level
unsigned m_materialize = 0; // materialize(): a split-set drained
unsigned m_splits = 0; // splits produced by iterator::next()
unsigned m_pushes = 0; // candidate <D,N> offered to push()
unsigned m_oracle_prunes = 0; // candidates dropped by the lookahead oracle
unsigned m_intersect = 0; // intersect() calls
unsigned m_intersect_pairs = 0; // pairs formed by intersect() cross-products
unsigned m_complement = 0; // complement() calls
unsigned m_giveups = 0; // iterator give-ups (unsupported/weak/overrun)
unsigned m_threshold_overruns = 0; // threshold hits (intersect/complement/iterator)
unsigned m_max_split_set = 0; // largest materialized split-set seen
unsigned m_simplify = 0; // simplify() calls
void reset() { *this = split_stats(); }
};
class seq_split {
ast_manager& m;
seq_rewriter& m_rw; // for mk_re_append + manager / seq_util access
@ -81,6 +100,7 @@ class seq_split {
func_decl_ref m_d_empty, m_d_single, m_d_fromre, m_d_union,
m_d_inter, m_d_compl, m_d_lcat, m_d_rcat;
expr_ref m_empty_app; // cached nullary `empty` term
mutable split_stats m_stats; // performance counters (see -st)
seq_util& seq() const;
seq_util::rex& re() const;
@ -151,6 +171,10 @@ class seq_split {
public:
explicit seq_split(seq_rewriter& rw);
// Performance counters (read via nseq -st).
split_stats const& stats() const { return m_stats; }
void reset_stats() { m_stats.reset(); }
// Lazy split enumerator. Holds the suspended split-set worklist and produces
// the concrete splits <D, N> one at a time, on demand, instead of computing
// them all up front. Obtain one from seq_split::iterate (or construct it