mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2026-03-08 06:14:52 +00:00
Code Activity
z3/src/ast/euf/euf_sgraph.cpp
copilot-swe-agent[bot] 150f1fe2ea Revert is_concat changes, add ZIPT URL, implement snode/sgraph operations and tests 
- Revert is_str_concat/is_re_concat to original form (PR #8820 review)
- Add ZIPT URL (https://github.com/CEisenhofer/ZIPT) to euf_sgraph.h
- Add snode::at() for token indexing and collect_tokens() for enumeration
- Add sgraph factory methods: mk_var, mk_char, mk_empty, mk_concat
- Add sgraph drop operations: drop_first, drop_last, drop_left, drop_right
- Add sgraph substitution: subst(snode*, snode*, snode*)
- Add Brzozowski derivative via seq_rewriter::mk_derivative
- Add minterm computation from regex predicates
- Add 7 new unit tests covering all new operations with complex concats

Co-authored-by: NikolajBjorner <56730610+NikolajBjorner@users.noreply.github.com>
2026-03-02 19:28:32 +00:00

551 lines
17 KiB
C++
Raw Blame History

/*++
Copyright (c) 2026 Microsoft Corporation
Module Name:
euf_sgraph.cpp
Abstract:
Sequence/string graph implementation
Author:
Nikolaj Bjorner (nbjorner) 2026-03-01
Clemens Eisenhofer 2026-03-01
--*/
#include "ast/euf/euf_sgraph.h"
#include "ast/euf/euf_seq_plugin.h"
#include "ast/arith_decl_plugin.h"
#include "ast/ast_pp.h"
namespace euf {
sgraph::sgraph(ast_manager& m):
m(m),
m_seq(m),
m_rewriter(m),
m_egraph(m),
m_exprs(m),
m_str_sort(m_seq.str.mk_string_sort(), m) {
// create seq_plugin and register it with the egraph
m_egraph.add_plugin(alloc(seq_plugin, m_egraph));
// register on_make callback so sgraph creates snodes for new enodes
std::function<void(enode*)> on_make = [this](enode* n) {
expr* e = n->get_expr();
if (m_seq.is_seq(e) || m_seq.is_re(e))
mk(e);
};
m_egraph.set_on_make(on_make);
}
sgraph::~sgraph() {
}
snode_kind sgraph::classify(expr* e) const {
if (!is_app(e))
return snode_kind::s_other;
if (m_seq.str.is_empty(e))
return snode_kind::s_empty;
if (m_seq.str.is_string(e)) {
zstring s;
if (m_seq.str.is_string(e, s) && s.empty())
return snode_kind::s_empty;
return snode_kind::s_other;
}
if (m_seq.str.is_concat(e))
return snode_kind::s_concat;
if (m_seq.str.is_unit(e)) {
expr* ch = to_app(e)->get_arg(0);
if (m_seq.is_const_char(ch))
return snode_kind::s_char;
return snode_kind::s_unit;
}
if (m_seq.str.is_power(e))
return snode_kind::s_power;
if (m_seq.re.is_star(e))
return snode_kind::s_star;
if (m_seq.re.is_loop(e))
return snode_kind::s_loop;
if (m_seq.re.is_union(e))
return snode_kind::s_union;
if (m_seq.re.is_intersection(e))
return snode_kind::s_intersect;
if (m_seq.re.is_complement(e))
return snode_kind::s_complement;
if (m_seq.re.is_empty(e))
return snode_kind::s_fail;
if (m_seq.re.is_full_char(e))
return snode_kind::s_full_char;
if (m_seq.re.is_full_seq(e))
return snode_kind::s_full_seq;
if (m_seq.re.is_to_re(e))
return snode_kind::s_to_re;
if (m_seq.str.is_in_re(e))
return snode_kind::s_in_re;
// uninterpreted constants of string sort are variables
if (is_uninterp_const(e) && m_seq.is_seq(e->get_sort()))
return snode_kind::s_var;
return snode_kind::s_other;
}
void sgraph::compute_metadata(snode* n) {
switch (n->m_kind) {
case snode_kind::s_empty:
n->m_ground = true;
n->m_regex_free = true;
n->m_nullable = true;
n->m_level = 0;
n->m_length = 0;
break;
case snode_kind::s_char:
n->m_ground = true;
n->m_regex_free = true;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_var:
n->m_ground = false;
n->m_regex_free = true;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_unit:
n->m_ground = n->num_args() > 0 ? n->arg(0)->is_ground() : true;
n->m_regex_free = true;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_concat: {
SASSERT(n->num_args() == 2);
snode* l = n->arg(0);
snode* r = n->arg(1);
n->m_ground = l->is_ground() && r->is_ground();
n->m_regex_free = l->is_regex_free() && r->is_regex_free();
n->m_nullable = l->is_nullable() && r->is_nullable();
n->m_level = std::max(l->level(), r->level()) + 1;
n->m_length = l->length() + r->length();
++m_stats.m_num_concat;
break;
}
case snode_kind::s_power: {
// s^n: nullable follows base, consistent with ZIPT's PowerToken
// the exponent n is assumed to be a symbolic integer, may or may not be zero
SASSERT(n->num_args() >= 1);
snode* base = n->arg(0);
n->m_ground = base->is_ground();
n->m_regex_free = base->is_regex_free();
n->m_nullable = base->is_nullable();
n->m_level = 1;
n->m_length = 1;
++m_stats.m_num_power;
break;
}
case snode_kind::s_star:
SASSERT(n->num_args() == 1);
n->m_ground = n->arg(0)->is_ground();
n->m_regex_free = false;
n->m_nullable = true;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_loop:
n->m_ground = n->num_args() > 0 ? n->arg(0)->is_ground() : true;
n->m_regex_free = false;
n->m_nullable = false; // depends on lower bound
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_union:
SASSERT(n->num_args() == 2);
n->m_ground = n->arg(0)->is_ground() && n->arg(1)->is_ground();
n->m_regex_free = false;
n->m_nullable = n->arg(0)->is_nullable() || n->arg(1)->is_nullable();
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_intersect:
SASSERT(n->num_args() == 2);
n->m_ground = n->arg(0)->is_ground() && n->arg(1)->is_ground();
n->m_regex_free = false;
n->m_nullable = n->arg(0)->is_nullable() && n->arg(1)->is_nullable();
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_complement:
SASSERT(n->num_args() == 1);
n->m_ground = n->arg(0)->is_ground();
n->m_regex_free = false;
n->m_nullable = !n->arg(0)->is_nullable();
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_fail:
n->m_ground = true;
n->m_regex_free = false;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_full_char:
n->m_ground = true;
n->m_regex_free = false;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_full_seq:
n->m_ground = true;
n->m_regex_free = false;
n->m_nullable = true;
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_to_re:
SASSERT(n->num_args() == 1);
n->m_ground = n->arg(0)->is_ground();
n->m_regex_free = false;
n->m_nullable = n->arg(0)->is_nullable();
n->m_level = 1;
n->m_length = 1;
break;
case snode_kind::s_in_re:
SASSERT(n->num_args() == 2);
n->m_ground = n->arg(0)->is_ground() && n->arg(1)->is_ground();
n->m_regex_free = false;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
default:
n->m_ground = true;
n->m_regex_free = true;
n->m_nullable = false;
n->m_level = 1;
n->m_length = 1;
break;
}
}
snode* sgraph::mk_snode(expr* e, snode_kind k, unsigned num_args, snode* const* args) {
unsigned id = m_nodes.size();
snode* n = snode::mk(m_region, e, k, id, num_args, args);
compute_metadata(n);
m_nodes.push_back(n);
m_exprs.push_back(e);
if (e) {
unsigned eid = e->get_id();
m_expr2snode.reserve(eid + 1, nullptr);
m_expr2snode[eid] = n;
}
++m_stats.m_num_nodes;
return n;
}
snode* sgraph::mk(expr* e) {
SASSERT(e);
snode* n = find(e);
if (n)
return n;
snode_kind k = classify(e);
if (!is_app(e))
return mk_snode(e, k, 0, nullptr);
app* a = to_app(e);
unsigned arity = a->get_num_args();
// recursively register children
// for seq/re children, create classified snodes
// for other children (e.g. integer exponents), create s_other snodes
snode_vector child_nodes;
for (unsigned i = 0; i < arity; ++i) {
expr* ch = a->get_arg(i);
snode* cn = mk(ch);
child_nodes.push_back(cn);
}
return mk_snode(e, k, child_nodes.size(), child_nodes.data());
}
snode* sgraph::find(expr* e) const {
if (!e)
return nullptr;
unsigned eid = e->get_id();
if (eid < m_expr2snode.size())
return m_expr2snode[eid];
return nullptr;
}
enode* sgraph::mk_enode(expr* e) {
enode* n = m_egraph.find(e);
if (n) return n;
enode_vector args;
if (is_app(e)) {
for (expr* arg : *to_app(e)) {
enode* a = mk_enode(arg);
args.push_back(a);
}
}
return m_egraph.mk(e, 0, args.size(), args.data());
}
void sgraph::push() {
m_scopes.push_back(m_nodes.size());
++m_num_scopes;
m_egraph.push();
}
void sgraph::pop(unsigned num_scopes) {
if (num_scopes == 0)
return;
SASSERT(num_scopes <= m_num_scopes);
unsigned new_lvl = m_num_scopes - num_scopes;
unsigned old_sz = m_scopes[new_lvl];
for (unsigned i = m_nodes.size(); i-- > old_sz; ) {
snode* n = m_nodes[i];
if (n->get_expr()) {
unsigned eid = n->get_expr()->get_id();
if (eid < m_expr2snode.size())
m_expr2snode[eid] = nullptr;
}
}
m_nodes.shrink(old_sz);
m_exprs.shrink(old_sz);
m_scopes.shrink(new_lvl);
m_num_scopes = new_lvl;
m_egraph.pop(num_scopes);
}
snode* sgraph::mk_var(symbol const& name) {
expr_ref e(m.mk_const(name, m_str_sort), m);
return mk(e);
}
snode* sgraph::mk_char(unsigned ch) {
expr_ref c(m_seq.str.mk_char(ch), m);
expr_ref u(m_seq.str.mk_unit(c), m);
return mk(u);
}
snode* sgraph::mk_empty() {
expr_ref e(m_seq.str.mk_empty(m_str_sort), m);
return mk(e);
}
snode* sgraph::mk_concat(snode* a, snode* b) {
if (a->is_empty()) return b;
if (b->is_empty()) return a;
expr_ref e(m_seq.str.mk_concat(a->get_expr(), b->get_expr()), m);
return mk(e);
}
snode* sgraph::drop_first(snode* n) {
if (n->is_empty() || n->is_token())
return mk_empty();
SASSERT(n->is_concat());
snode* l = n->arg(0);
snode* r = n->arg(1);
if (l->is_token() || l->is_empty())
return r;
return mk_concat(drop_first(l), r);
}
snode* sgraph::drop_last(snode* n) {
if (n->is_empty() || n->is_token())
return mk_empty();
SASSERT(n->is_concat());
snode* l = n->arg(0);
snode* r = n->arg(1);
if (r->is_token() || r->is_empty())
return l;
return mk_concat(l, drop_last(r));
}
snode* sgraph::drop_left(snode* n, unsigned count) {
for (unsigned i = 0; i < count && !n->is_empty(); ++i)
n = drop_first(n);
return n;
}
snode* sgraph::drop_right(snode* n, unsigned count) {
for (unsigned i = 0; i < count && !n->is_empty(); ++i)
n = drop_last(n);
return n;
}
snode* sgraph::subst(snode* n, snode* var, snode* replacement) {
if (n == var)
return replacement;
if (n->is_empty() || n->is_char())
return n;
if (n->is_concat())
return mk_concat(subst(n->arg(0), var, replacement),
subst(n->arg(1), var, replacement));
// for non-concat compound nodes (power, star, etc.), no substitution into children
return n;
}
snode* sgraph::brzozowski_deriv(snode* re, snode* elem) {
expr* re_expr = re->get_expr();
expr* elem_expr = elem->get_expr();
if (!re_expr || !elem_expr)
return nullptr;
// unwrap str.unit to get the character expression
expr* ch = nullptr;
if (m_seq.str.is_unit(elem_expr, ch))
elem_expr = ch;
expr_ref result = m_rewriter.mk_derivative(elem_expr, re_expr);
if (!result)
return nullptr;
return mk(result);
}
void sgraph::collect_re_predicates(snode* re, expr_ref_vector& preds) {
if (!re || !re->get_expr())
return;
expr* e = re->get_expr();
expr* ch = nullptr, *lo = nullptr, *hi = nullptr;
// leaf regex predicates: character ranges and single characters
if (m_seq.re.is_range(e, lo, hi)) {
preds.push_back(e);
return;
}
if (m_seq.re.is_to_re(e))
return;
if (m_seq.re.is_full_char(e))
return;
if (m_seq.re.is_full_seq(e))
return;
if (m_seq.re.is_empty(e))
return;
// recurse into compound regex operators
for (unsigned i = 0; i < re->num_args(); ++i)
collect_re_predicates(re->arg(i), preds);
}
void sgraph::compute_minterms(snode* re, snode_vector& minterms) {
// extract character predicates from the regex
expr_ref_vector preds(m);
collect_re_predicates(re, preds);
if (preds.empty()) {
// no predicates means the whole alphabet is one minterm
// represented by full_char
expr_ref fc(m_seq.re.mk_full_char(m_str_sort), m);
minterms.push_back(mk(fc));
return;
}
// generate minterms as conjunctions/negations of predicates
// for n predicates, there are up to 2^n minterms
unsigned n = preds.size();
for (unsigned mask = 0; mask < (1u << n); ++mask) {
expr_ref_vector conj(m);
for (unsigned i = 0; i < n; ++i) {
if (mask & (1u << i))
conj.push_back(preds.get(i));
else
conj.push_back(m_seq.re.mk_complement(preds.get(i)));
}
// intersect all terms
expr_ref mt(conj.get(0), m);
for (unsigned i = 1; i < conj.size(); ++i)
mt = m_seq.re.mk_inter(mt, conj.get(i));
minterms.push_back(mk(mt));
}
}
std::ostream& sgraph::display(std::ostream& out) const {
auto kind_str = [](snode_kind k) -> char const* {
switch (k) {
case snode_kind::s_empty: return "empty";
case snode_kind::s_char: return "char";
case snode_kind::s_var: return "var";
case snode_kind::s_unit: return "unit";
case snode_kind::s_concat: return "concat";
case snode_kind::s_power: return "power";
case snode_kind::s_star: return "star";
case snode_kind::s_loop: return "loop";
case snode_kind::s_union: return "union";
case snode_kind::s_intersect: return "intersect";
case snode_kind::s_complement: return "complement";
case snode_kind::s_fail: return "fail";
case snode_kind::s_full_char: return "full_char";
case snode_kind::s_full_seq: return "full_seq";
case snode_kind::s_to_re: return "to_re";
case snode_kind::s_in_re: return "in_re";
case snode_kind::s_other: return "other";
}
return "?";
};
for (snode* n : m_nodes) {
out << "snode[" << n->id() << "] "
<< kind_str(n->kind())
<< " level=" << n->level()
<< " len=" << n->length()
<< " ground=" << n->is_ground()
<< " rfree=" << n->is_regex_free()
<< " nullable=" << n->is_nullable();
if (n->num_args() > 0) {
out << " args=(";
for (unsigned i = 0; i < n->num_args(); ++i) {
if (i > 0) out << ", ";
out << n->arg(i)->id();
}
out << ")";
}
if (n->get_expr())
out << " expr=" << mk_pp(n->get_expr(), m);
out << "\n";
}
return out;
}
void sgraph::collect_statistics(statistics& st) const {
st.update("seq-graph-nodes", m_stats.m_num_nodes);
st.update("seq-graph-concat", m_stats.m_num_concat);
st.update("seq-graph-power", m_stats.m_num_power);
st.update("seq-graph-hash-hits", m_stats.m_num_hash_hits);
m_egraph.collect_statistics(st);
}
}
View git blame Copy permalink