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add some review comments

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2018-06-09 10:57:57 -07:00 committed by Arie Gurfinkel
parent 2e44850df9
commit 14696f03f7
2 changed files with 619 additions and 0 deletions

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/**++
Copyright (c) Arie Gurfinkel
Module Name:
qe_term_graph.cpp
Abstract:
Equivalence graph of terms
Author:
Arie Gurfinkel
Notes:
--*/
#include "util/util.h"
#include "ast/ast_pp.h"
#include "ast/ast_util.h"
#include "ast/for_each_expr.h"
#include "qe/qe_term_graph.h"
namespace qe {
class term {
// -- an app represented by this term
app* m_app;
// -- root of the equivalence class
term* m_root;
// -- next element in the equivalence class (cyclic linked list)
term* m_next;
// -- eq class size
unsigned m_class_size;
// -- general purpose mark
unsigned m_mark:1;
// -- general purpose second mark
unsigned m_mark2:1;
// -- is an interpreted constant
unsigned m_interpreted:1;
// -- terms that contain this term as a child
//ptr_vector<term> m_uses;
// ptr_vector<term> m_args;
public:
term(app* a) : m_app(a), m_root(this), m_next(this),
m_class_size(1), m_mark(false), m_mark2(false),
m_interpreted(false) {}
~term() {}
unsigned get_id() const {return m_app->get_id();}
bool is_marked() const {return m_mark;}
void set_mark(bool v){m_mark = v;}
bool is_marked2() const {return m_mark2;}
void set_mark2(bool v){m_mark2 = v;}
bool is_interpreted() const {return m_interpreted;}
void mark_as_interpreted() {m_interpreted=true;}
app* get_app() const {return m_app;}
term &get_root() const {return *m_root;}
bool is_root() const {return m_root == this;}
void set_root(term &r) {m_root = &r;}
term &get_next() const {return *m_next;}
unsigned get_class_size() const {return m_class_size;}
void merge_eq_class(term &b) {
std::swap(this->m_next, b.m_next);
m_class_size += b.get_class_size();
// -- reset (useful for debugging)
b.m_class_size = 0;
}
// -- make this term the root of its equivalence class
void mk_root() {
if (is_root()) return;
term *curr = this;
do {
if (curr->is_root()) {
// found previous root
SASSERT(curr != this);
m_class_size = curr->get_class_size();
curr->m_class_size = 0;
}
curr->set_root(*this);
curr = &curr->get_next();
}
while (curr != this);
}
};
class arith_term_graph_plugin : public term_graph_plugin {
term_graph &m_g;
ast_manager &m;
arith_util m_arith;
public:
arith_term_graph_plugin(term_graph &g) :
term_graph_plugin (g.get_ast_manager().mk_family_id("arith")),
m_g(g), m(g.get_ast_manager()), m_arith(m) {(void)m_g;}
virtual ~arith_term_graph_plugin() {}
bool mk_eq_core (expr *_e1, expr *_e2, app_ref &res) {
expr *e1, *e2;
e1 = _e1;
e2 = _e2;
if (m_arith.is_zero(e1)) {
std::swap(e1, e2);
}
// y + -1*x == 0 --> y = x
expr *a0 = 0, *a1 = 0, *x = 0;
if (m_arith.is_zero(e2) && m_arith.is_add(e1, a0, a1)) {
if (m_arith.is_times_minus_one(a1, x)) {
e1 = a0;
e2 = x;
}
else if (m_arith.is_times_minus_one(a0, x)) {
e1 = a1;
e2 = x;
}
}
res = m.mk_eq(e1, e2);
return true;
}
app* mk_le_zero(expr *arg) {
expr *e1, *e2, *e3;
// XXX currently disabled
if (m_arith.is_add(arg, e1, e2)) {
// e1-e2<=0 --> e1<=e2
if (m_arith.is_times_minus_one(e2, e3)) {
return m_arith.mk_le(e1, e3);
}
// -e1+e2<=0 --> e2<=e1
else if (m_arith.is_times_minus_one(e1, e3)) {
return m_arith.mk_le(e2, e3);
}
}
return m_arith.mk_le(arg, mk_zero());
}
app* mk_ge_zero(expr *arg) {
expr *e1, *e2, *e3;
// XXX currently disabled
if (m_arith.is_add(arg, e1, e2)) {
// e1-e2>=0 --> e1>=e2
if (m_arith.is_times_minus_one(e2, e3)) {
return m_arith.mk_ge(e1, e3);
}
// -e1+e2>=0 --> e2>=e1
else if (m_arith.is_times_minus_one(e1, e3)) {
return m_arith.mk_ge(e2, e3);
}
}
return m_arith.mk_ge(arg, mk_zero());
}
bool mk_le_core (expr *arg1, expr * arg2, app_ref &result) {
// t <= -1 ==> t < 0 ==> ! (t >= 0)
rational n;
if (m_arith.is_int (arg1) && m_arith.is_minus_one (arg2)) {
result = m.mk_not (mk_ge_zero (arg1));
return true;
}
else if (m_arith.is_zero(arg2)) {
result = mk_le_zero(arg1);
return true;
}
else if (m_arith.is_int(arg1) && m_arith.is_numeral(arg2, n) && n < 0) {
// t <= n ==> t < n + 1 ==> ! (t >= n + 1)
result = m.mk_not(m_arith.mk_ge(arg1, m_arith.mk_numeral(n+1, true)));
return true;
}
return false;
}
expr * mk_zero () {return m_arith.mk_numeral (rational (0), true);}
bool is_one (expr const * n) const {
rational val;
return m_arith.is_numeral (n, val) && val.is_one ();
}
bool mk_ge_core (expr * arg1, expr * arg2, app_ref &result) {
// t >= 1 ==> t > 0 ==> ! (t <= 0)
rational n;
if (m_arith.is_int (arg1) && is_one (arg2)) {
result = m.mk_not (mk_le_zero (arg1));
return true;
}
else if (m_arith.is_zero(arg2)) {
result = mk_ge_zero(arg1);
return true;
}
else if (m_arith.is_int(arg1) && m_arith.is_numeral(arg2, n) && n > 0) {
// t >= n ==> t > n - 1 ==> ! (t <= n - 1)
result = m.mk_not(m_arith.mk_le(arg1, m_arith.mk_numeral(n-1, true)));
return true;
}
return false;
}
virtual app_ref process_lit (app *_lit) {
app *lit = _lit;
expr *e1, *e2;
// strip negation
bool is_neg = m.is_not(lit);
if (is_neg) {
lit = to_app(to_app(lit)->get_arg(0));
}
app_ref res(m);
res = lit;
if (m.is_eq (lit, e1, e2)) {
mk_eq_core(e1, e2, res);
}
else if (m_arith.is_le(lit, e1, e2)) {
mk_le_core(e1, e2, res);
}
else if (m_arith.is_ge(lit, e1, e2)) {
mk_ge_core(e1, e2, res);
}
// restore negation
if (is_neg) {
res = m.mk_not(res);
}
return res;
}
};
term_graph::term_graph(ast_manager &man) : m(man), m_lits(m), m_pinned(m) {
m_plugins.register_plugin (alloc(arith_term_graph_plugin, *this));
}
term_graph::~term_graph() {
reset();
}
static family_id get_family_id(ast_manager &m, app *lit) {
family_id fid = null_family_id;
expr *e1, *e2, *e3;
// strip negation
if (!m.is_not (lit, e1)) { e1 = lit; }
// deal with equality using sort of range
if (m.is_eq (e1, e2, e3)) {
fid = get_sort (e2)->get_family_id();
}
// extract family_id of top level app
else {
fid = to_app(e1)->get_decl()->get_family_id();
}
return fid;
}
void term_graph::add_lit(app *l) {
app_ref lit(m);
family_id fid = get_family_id (m, l);
term_graph_plugin *pin = m_plugins.get_plugin(fid);
if (pin) {
lit = pin->process_lit(l);
} else {
lit = l;
}
m_lits.push_back(lit);
internalize_lit(lit);
}
bool term_graph::is_internalized(app *a) {
return m_app2term.contains(a->get_id());
}
term* term_graph::get_term(app *a) {
term *res;
return m_app2term.find (a->get_id(), res) ? res : nullptr;
}
term *term_graph::mk_term(app *a) {
term * t = alloc(term, a);
if (a->get_num_args() == 0 && m.is_unique_value(a)){
t->mark_as_interpreted();
}
m_terms.push_back(t);
m_app2term.insert(a->get_id(), t);
return t;
}
term *term_graph::internalize_term(app *t) {
term *res = get_term(t);
if (!res) {
for (expr * arg : *t) {
SASSERT(is_app(arg));
internalize_term(::to_app(arg));
}
res = mk_term(t);
}
return res;
}
void term_graph::internalize_eq(app *a1, app* a2) {
internalize_lit(a1);
internalize_lit(a2);
merge(get_term(a1)->get_root(), get_term(a2)->get_root());
}
void term_graph::internalize_lit(app* lit) {
if (is_internalized(lit)) return;
expr *e1, *e2;
if (m.is_eq (lit, e1, e2)) {
SASSERT(is_app(e1));
SASSERT(is_app(e2));
internalize_eq (::to_app(e1), ::to_app(e2));
}
else {
// NSB: this is thrown away.
// Is caller responsible for maintaining other predicates than equalities?
internalize_term(lit);
}
}
void term_graph::merge (term &t1, term &t2) {
SASSERT(t1.is_root());
SASSERT(t2.is_root());
if (&t1 == &t2) return;
term *a = &t1;
term *b = &t2;
if (a->get_class_size() > b->get_class_size()) {
std::swap(a, b);
}
// make 'a' be the root of the equivalence class of 'b'
b->set_root(*a);
for (term *it = &b->get_next(); it != b; it = &it->get_next()) {
it->set_root(*a);
}
// merge equivalence classes
a->merge_eq_class(*b);
// -- merge might have invalidated term2map cache
m_term2app.reset();
m_pinned.reset();
}
app* term_graph::mk_app_core (app *a) {
expr_ref_vector kids(m);
for (expr * arg : *a) {
kids.push_back (mk_app(::to_app(arg)));
}
app* res = m.mk_app(a->get_decl(), a->get_num_args(), kids.c_ptr());
m_pinned.push_back(res);
return res;
}
app_ref term_graph::mk_app(term const &r) {
SASSERT(r.is_root());
if (r.get_app()->get_num_args() == 0) {
return app_ref(r.get_app(), m);
}
app* res;
if (m_term2app.find(r.get_id(), res)) {
return app_ref(res, m);
}
res = mk_app_core (r.get_app());
m_term2app.insert(r.get_id(), res);
return app_ref(res, m);
}
app_ref term_graph::mk_app(app *a) {
term *t = get_term(a);
if (!t)
return app_ref(a, m);
else
return mk_app(t->get_root());
}
void term_graph::mk_equalities(term const &t, app_ref_vector &out) {
SASSERT(t.is_root());
app_ref rep(mk_app(t), m);
for (term *it = &t.get_next(); it != &t; it = &it->get_next()) {
app* mem = mk_app_core(it->get_app());
out.push_back (m.mk_eq (rep, mem));
}
}
void term_graph::mk_all_equalities(term const &t, app_ref_vector &out) {
mk_equalities(t, out);
for (term *it = &t.get_next(); it != &t; it = &it->get_next ()) {
app* a1 = mk_app_core (it->get_app());
for (term *it2 = &it->get_next(); it2 != &t; it2 = &it2->get_next()) {
app *a2;
a2 = mk_app_core(it2->get_app());
out.push_back (m.mk_eq (a1, a2));
}
}
}
void term_graph::reset_marks() {
for (term * t : m_terms) {
t->set_mark(false);
}
}
/// Order of preference for roots of equivalence classes
/// XXX This should be factored out to let clients control the preference
bool term_graph::term_le(term const &t1, term const &t2) {
// prefer constants over applications
// prefer uninterpreted constants over values
// prefer smaller expressions over larger ones
app *a1, *a2;
a1 = t1.get_app();
a2 = t2.get_app();
if (a1->get_num_args() == 0 && a2->get_num_args() > 0) {
return true;
}
// NSB: how does this possibly define an order?
if (a1->get_num_args() == a2->get_num_args()) {
return m.is_value(a2);
}
unsigned sz1 = get_num_exprs(a1);
unsigned sz2 = get_num_exprs(a2);
return sz1 < sz2;
}
void term_graph::pick_root (term &t) {
term *r = &t;
for (term *it = &t.get_next(); it != &t; it = &it->get_next()) {
it->set_mark(true);
if (term_le(*it, *r)) { r = it; }
}
// -- if found something better, make it the new root
if (r != &t) {
r->mk_root();
}
}
/// Choose better roots for equivalence classes
void term_graph::pick_roots() {
for (term* t : m_terms) {
if (!t->is_marked() && t->is_root())
pick_root(*t);
}
reset_marks();
}
void term_graph::display(std::ostream &out) {
for (term * t : m_terms) {
out << mk_pp(t->get_app(), m) << " is root " << t->is_root()
<< " cls sz " << t->get_class_size()
<< " term " << t
<< "\n";
}
}
void term_graph::to_lits (app_ref_vector &lits, bool all_equalities) {
pick_roots();
for (app * a : m_lits) {
if (is_internalized(a)) {
lits.push_back (mk_app(a));
}
}
for (term * t : m_terms) {
if (!t->is_root())
continue;
else if (all_equalities)
mk_all_equalities (*t, lits);
else
mk_equalities(*t, lits);
}
}
void term_graph::to_lits (expr_ref_vector &lits, bool all_equalities) {
app_ref_vector out(m);
to_lits (out, all_equalities);
for (app* a : out) {
lits.push_back(a);
}
}
app_ref term_graph::to_app() {
app_ref_vector lits(m);
to_lits(lits);
return mk_and(lits);
}
void term_graph::reset() {
m_term2app.reset();
m_pinned.reset();
m_app2term.reset();
std::for_each(m_terms.begin(), m_terms.end(), delete_proc<term>());
m_terms.reset();
m_lits.reset();
}
}

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/**++
Copyright (c) Arie Gurfinkel
Module Name:
qe_term_graph.h
Abstract:
Equivalence graph of terms
Author:
Arie Gurfinkel
Notes:
--*/
#ifndef QE_TERM_GRAPH_H__
#define QE_TERM_GRAPH_H__
#include "ast/ast.h"
#include "util/plugin_manager.h"
namespace qe {
class term;
class term_graph_plugin {
family_id m_id;
public:
term_graph_plugin(family_id fid) : m_id(fid) {}
virtual ~term_graph_plugin() {}
family_id get_family_id() const {return m_id;}
/// Process (and potentially augment) a literal
virtual app_ref process_lit (app *lit) = 0;
};
class term_graph {
ast_manager &m;
ptr_vector<term> m_terms;
app_ref_vector m_lits;
u_map<term* > m_app2term;
app_ref_vector m_pinned;
u_map<app*> m_term2app;
plugin_manager<term_graph_plugin> m_plugins;
void merge(term &t1, term &t2);
term *mk_term(app *t);
term *get_term(app *t);
term *internalize_term(app *t);
void internalize_eq(app *a1, app *a2);
void internalize_lit(app *lit);
bool is_internalized(app *a);
bool term_le(term const &t1, term const &t2);
void pick_root (term &t);
void pick_roots();
void reset_marks();
app *mk_app_core(app* a);
app_ref mk_app(term const &t);
app_ref mk_app(app *a);
void mk_equalities(term const &t, app_ref_vector &out);
void mk_all_equalities(term const &t, app_ref_vector &out);
void display(std::ostream &out);
public:
term_graph(ast_manager &man);
~term_graph();
ast_manager &get_ast_manager() const { return m;}
void add_lit(app *lit);
void add_lits(expr_ref_vector const &lits) {
for (expr* e : lits) add_lit(::to_app(e));
}
void reset();
void to_lits(app_ref_vector &lits, bool all_equalities = false);
void to_lits(expr_ref_vector &lits, bool all_equalities = false);
app_ref to_app();
};
}
#endif