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Power base compression

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This commit is contained in:
CEisenhofer 2026-03-12 13:24:20 +01:00
parent bee9fd82f0
commit e8354a783a
2 changed files with 42 additions and 5 deletions
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45
src/smt/seq/seq_nielsen.cpp
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@ -870,7 +870,7 @@ namespace seq {
// --- nodes ---
for (nielsen_node const* n : m_nodes) {
out << "\t" << n->id() << " [label=<"
out << " " << n->id() << " [label=<"
<< n->id() << ": ";
n->display_html(out, m);
// append conflict reason if this is a direct conflict
@ -894,7 +894,7 @@ namespace seq {
// --- edges ---
for (nielsen_node const* n : m_nodes) {
for (nielsen_edge const* e : n->outgoing()) {
out << "\t" << n->id() << " -> " << e->tgt()->id() << " [label=<";
out << " " << n->id() << " -> " << e->tgt()->id() << " [label=<";
// edge label: substitutions joined by <br/>
bool first = true;
@ -955,7 +955,7 @@ namespace seq {
// backedge as dotted arrow
if (n->backedge())
out << "\t" << n->id() << " -> " << n->backedge()->id()
out << " " << n->id() << " -> " << n->backedge()->id()
<< " [style=dotted];\n";
}
@ -3131,10 +3131,47 @@ namespace seq {
bool nielsen_graph::fire_gpower_intro(
nielsen_node* node, str_eq const& eq,
euf::snode* var, euf::snode_vector const& ground_prefix) {
euf::snode* var, euf::snode_vector const& ground_prefix_orig) {
ast_manager& m = m_sg.get_manager();
arith_util arith(m);
seq_util& seq = m_sg.get_seq_util();
// Compress repeated patterns in the ground prefix (mirrors ZIPT's LcpCompressionFull).
// E.g., [a,b,a,b] has minimal period 2 → use [a,b] as the power base.
// This ensures we use the minimal repeating unit: x = (ab)^n · suffix
// instead of x = (abab)^n · suffix.
euf::snode_vector ground_prefix;
unsigned n = ground_prefix_orig.size();
unsigned period = n;
for (unsigned p = 1; p <= n / 2; ++p) {
if (n % p != 0) continue;
bool match = true;
for (unsigned i = p; i < n && match; ++i)
match = (ground_prefix_orig[i]->id() == ground_prefix_orig[i % p]->id());
if (match) { period = p; break; }
}
for (unsigned i = 0; i < period; ++i)
ground_prefix.push_back(ground_prefix_orig[i]);
// If the compressed prefix is a single power snode, unwrap it to use
// its base tokens, avoiding nested powers.
// E.g., [(ab)^3] → [a, b] so we get (ab)^n instead of ((ab)^3)^n.
// (mirrors ZIPT: if b.Length == 1 && b is PowerToken pt => b = pt.Base)
if (ground_prefix.size() == 1 && ground_prefix[0]->is_power()) {
expr* base_e = get_power_base_expr(ground_prefix[0]);
if (base_e) {
euf::snode* base_sn = m_sg.mk(base_e);
if (base_sn) {
euf::snode_vector base_toks;
base_sn->collect_tokens(base_toks);
if (!base_toks.empty()) {
ground_prefix.reset();
ground_prefix.append(base_toks);
}
}
}
}
unsigned base_len = ground_prefix.size();
// Build base string expression from ground prefix tokens.