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convert reduce-args to a simplifier

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- convert reduce-args to a simplifier. Currently exposed as reduce-args2 tactic until the old tactic code gets removed.
- bug fixes in model_reconstruction trail
  - allow multiple defs to be added with same pool of removed formulas
  - fix tracking of function symbols instead of expressions to filter replay
- add nla_divisions to track (cheap) divisibility lemmas.
-
This commit is contained in:
Nikolaj Bjorner 2023-01-28 20:12:14 -08:00
parent 246d6f7b77
commit 8ea49eed8e
23 changed files with 740 additions and 92 deletions
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src/ast/simplifiers/reduce_args_simplifier.cpp Normal file
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/*++
Copyright (c) 2012 Microsoft Corporation
Module Name:
reduce_args_simplifier.cpp
Abstract:
Reduce the number of arguments in function applications.
Author:
Leonardo (leonardo) 2012-02-19
Notes:
--*/
#include "util/map.h"
#include "ast/ast_smt2_pp.h"
#include "ast/ast_util.h"
#include "ast/has_free_vars.h"
#include "ast/rewriter/rewriter_def.h"
#include "ast/simplifiers/dependent_expr_state.h"
/**
\brief Reduce the number of arguments in function applications.
Example, suppose we have a function f with 2 arguments.
There are 1000 applications of this function, but the first argument is always "a", "b" or "c".
Thus, we replace the f(t1, t2)
with
f_a(t2) if t1 = a
f_b(t2) if t2 = b
f_c(t2) if t2 = c
Since f_a, f_b, f_c are new symbols, satisfiability is preserved.
This transformation is very similar in spirit to the Ackermman's reduction.
This transformation should work in the following way:
1- Create a mapping decl2arg_map from declarations to tuples of booleans, an entry [f -> (true, false, true)]
means that f is a declaration with 3 arguments where the first and third arguments are always values.
2- Traverse the formula and populate the mapping.
For each function application f(t1, ..., tn) do
a) Create a boolean tuple (is_value(t1), ..., is_value(tn)) and do
the logical-and with the tuple that is already in the mapping. If there is no such tuple
in the mapping, we just add a new entry.
If all entries are false-tuples, then there is nothing to be done. The transformation is not applicable.
Now, we create a mapping decl2new_decl from (decl, val_1, ..., val_n) to decls. Note that, n may be different for each entry,
but it is the same for the same declaration.
For example, suppose we have [f -> (true, false, true)] in decl2arg_map, and applications f(1, a, 2), f(1, b, 2), f(1, b, 3), f(2, b, 3), f(2, c, 3) in the formula.
Then, decl2arg_map would contain
(f, 1, 2) -> f_1_2
(f, 1, 3) -> f_1_3
(f, 2, 3) -> f_2_3
where f_1_2, f_1_3 and f_2_3 are new function symbols.
Using the new map, we can replace the occurrences of f.
*/
class reduce_args_simplifier : public dependent_expr_simplifier {
bv_util m_bv;
static bool is_var_plus_offset(ast_manager& m, bv_util& bv, expr* e, expr*& base) {
expr *lhs, *rhs;
if (bv.is_bv_add(e, lhs, rhs) && bv.is_numeral(lhs))
base = rhs;
else
base = e;
return !has_free_vars(base);
}
static bool may_be_unique(ast_manager& m, bv_util& bv, expr* e, expr*& base) {
base = nullptr;
return m.is_unique_value(e) || is_var_plus_offset(m, bv, e, base);
}
static bool may_be_unique(ast_manager& m, bv_util& bv, expr* e) {
expr* base;
return may_be_unique(m, bv, e, base);
}
struct find_non_candidates_proc {
ast_manager & m;
bv_util & m_bv;
obj_hashtable<func_decl> & m_non_candidates;
find_non_candidates_proc(ast_manager & m, bv_util & bv, obj_hashtable<func_decl> & non_candidates):
m(m),
m_bv(bv),
m_non_candidates(non_candidates) {
}
void operator()(var * n) {}
void operator()(quantifier *n) {}
void operator()(app * n) {
if (!is_uninterp(n))
return;
func_decl * d;
if (n->get_num_args() == 0)
return; // ignore constants
d = n->get_decl();
if (m_non_candidates.contains(d))
return; // it is already in the set.
for (expr* arg : *n)
if (may_be_unique(m, m_bv, arg))
return;
m_non_candidates.insert(d);
}
};
/**
\brief Populate the table non_candidates with function declarations \c f
such that there is a function application (f t1 ... tn) where t1 ... tn are not values.
*/
void find_non_candidates(obj_hashtable<func_decl> & non_candidates) {
non_candidates.reset();
find_non_candidates_proc proc(m, m_bv, non_candidates);
expr_fast_mark1 visited;
for (auto i : indices())
quick_for_each_expr(proc, visited, m_fmls[i].fml());
TRACE("reduce_args", tout << "non_candidates:\n"; for (func_decl* d : non_candidates) tout << d->get_name() << "\n";);
}
struct populate_decl2args_proc {
reduce_args_simplifier& m_owner;
ast_manager & m;
bv_util & m_bv;
obj_hashtable<func_decl> & m_non_candidates;
obj_map<func_decl, bit_vector> & m_decl2args;
obj_map<func_decl, svector<expr*> > m_decl2base; // for args = base + offset
populate_decl2args_proc(reduce_args_simplifier& o, ast_manager & m, bv_util & bv, obj_hashtable<func_decl> & nc, obj_map<func_decl, bit_vector> & d):
m_owner(o), m(m), m_bv(bv), m_non_candidates(nc), m_decl2args(d) {}
void operator()(var * n) {}
void operator()(quantifier * n) {}
void operator()(app * n) {
if (n->get_num_args() == 0)
return; // ignore constants
func_decl * d = n->get_decl();
if (d->get_family_id() != null_family_id)
return; // ignore interpreted symbols
if (m_non_candidates.contains(d))
return; // declaration is not a candidate
if (m_owner.m_fmls.frozen(d))
return;
unsigned j = n->get_num_args();
obj_map<func_decl, bit_vector>::iterator it = m_decl2args.find_iterator(d);
expr* base;
if (it == m_decl2args.end()) {
m_decl2args.insert(d, bit_vector());
svector<expr*>& bases = m_decl2base.insert_if_not_there(d, svector<expr*>());
bases.resize(j);
it = m_decl2args.find_iterator(d);
SASSERT(it != m_decl2args.end());
it->m_value.reserve(j);
while (j > 0) {
--j;
it->m_value.set(j, may_be_unique(m, m_bv, n->get_arg(j), base));
bases[j] = base;
}
} else {
svector<expr*>& bases = m_decl2base[d];
SASSERT(j == it->m_value.size());
while (j > 0) {
--j;
it->m_value.set(j, it->m_value.get(j) && may_be_unique(m, m_bv, n->get_arg(j), base) && bases[j] == base);
}
}
}
};
void populate_decl2args(obj_hashtable<func_decl> & non_candidates,
obj_map<func_decl, bit_vector> & decl2args) {
expr_fast_mark1 visited;
decl2args.reset();
populate_decl2args_proc proc(*this, m, m_bv, non_candidates, decl2args);
for (auto i : indices())
quick_for_each_expr(proc, visited, m_fmls[i].fml());
// Remove all cases where the simplification is not applicable.
ptr_buffer<func_decl> bad_decls;
for (auto const& [k, v] : decl2args)
if (all_of(v, [&](auto b) { return !b;}))
bad_decls.push_back(k);
for (func_decl* a : bad_decls)
decl2args.erase(a);
TRACE("reduce_args", tout << "decl2args:" << std::endl;
for (auto const& [k, v] : decl2args) {
tout << k->get_name() << ": ";
for (unsigned i = 0; i < v.size(); ++i)
tout << (v.get(i) ? "1" : "0");
tout << std::endl;
});
}
struct arg2func_hash_proc {
bit_vector const & m_bv;
arg2func_hash_proc(bit_vector const & bv):m_bv(bv) {}
unsigned operator()(app const * n) const {
// compute the hash-code using only the arguments where m_bv is true.
unsigned a = 0x9e3779b9;
unsigned num_args = n->get_num_args();
for (unsigned i = 0; i < num_args; i++) {
if (!m_bv.get(i))
continue; // ignore argument
a = hash_u_u(a, n->get_arg(i)->get_id());
}
return a;
}
};
struct arg2func_eq_proc {
bit_vector const & m_bv;
arg2func_eq_proc(bit_vector const & bv):m_bv(bv) {}
bool operator()(app const * n1, app const * n2) const {
// compare only the arguments where m_bv is true
SASSERT(n1->get_num_args() == n2->get_num_args());
unsigned num_args = n1->get_num_args();
for (unsigned i = 0; i < num_args; i++) {
if (!m_bv.get(i))
continue; // ignore argument
if (n1->get_arg(i) != n2->get_arg(i))
return false;
}
return true;
}
};
typedef map<app *, func_decl *, arg2func_hash_proc, arg2func_eq_proc> arg2func;
typedef obj_map<func_decl, arg2func *> decl2arg2func_map;
struct reduce_args_ctx {
ast_manager & m;
decl2arg2func_map m_decl2arg2funcs;
reduce_args_ctx(ast_manager & m): m(m) {
}
~reduce_args_ctx() {
for (auto const& [_, map] : m_decl2arg2funcs) {
for (auto const& [k, v] : *map) {
m.dec_ref(k);
m.dec_ref(v);
}
dealloc(map);
}
}
};
struct reduce_args_rw_cfg : public default_rewriter_cfg {
ast_manager & m;
reduce_args_simplifier& m_owner;
obj_map<func_decl, bit_vector> & m_decl2args;
decl2arg2func_map & m_decl2arg2funcs;
reduce_args_rw_cfg(reduce_args_simplifier& owner, obj_map<func_decl, bit_vector> & decl2args, decl2arg2func_map & decl2arg2funcs):
m(owner.m),
m_owner(owner),
m_decl2args(decl2args),
m_decl2arg2funcs(decl2arg2funcs) {
}
br_status reduce_app(func_decl * f, unsigned num, expr * const * args, expr_ref & result, proof_ref & result_pr) {
result_pr = nullptr;
if (f->get_arity() == 0)
return BR_FAILED; // ignore constants
if (f->get_family_id() != null_family_id)
return BR_FAILED; // ignore interpreted symbols
obj_map<func_decl, bit_vector>::iterator it = m_decl2args.find_iterator(f);
if (it == m_decl2args.end())
return BR_FAILED;
bit_vector & bv = it->m_value;
arg2func *& map = m_decl2arg2funcs.insert_if_not_there(f, 0);
if (!map) {
map = alloc(arg2func, arg2func_hash_proc(bv), arg2func_eq_proc(bv));
}
app_ref tmp(m.mk_app(f, num, args), m);
func_decl *& new_f = map->insert_if_not_there(tmp, nullptr);
if (!new_f) {
// create fresh symbol
ptr_buffer<sort> domain;
unsigned arity = f->get_arity();
for (unsigned i = 0; i < arity; ++i) {
if (!bv.get(i))
domain.push_back(f->get_domain(i));
}
new_f = m.mk_fresh_func_decl(f->get_name(), symbol::null, domain.size(), domain.data(), f->get_range());
m.inc_ref(tmp);
m.inc_ref(new_f);
}
ptr_buffer<expr> new_args;
for (unsigned i = 0; i < num; i++) {
if (!bv.get(i))
new_args.push_back(args[i]);
}
result = m.mk_app(new_f, new_args.size(), new_args.data());
return BR_DONE;
}
};
struct reduce_args_rw : rewriter_tpl<reduce_args_rw_cfg> {
reduce_args_rw_cfg m_cfg;
public:
reduce_args_rw(reduce_args_simplifier & owner, obj_map<func_decl, bit_vector> & decl2args, decl2arg2func_map & decl2arg2funcs):
rewriter_tpl<reduce_args_rw_cfg>(owner.m, false, m_cfg),
m_cfg(owner, decl2args, decl2arg2funcs) {
}
};
void mk_mc(obj_map<func_decl, bit_vector> & decl2args, decl2arg2func_map & decl2arg2funcs, vector<dependent_expr> const& removed) {
ptr_buffer<expr> new_args;
var_ref_vector new_vars(m);
ptr_buffer<expr> new_eqs;
generic_model_converter * f_mc = alloc(generic_model_converter, m, "reduce_args");
for (auto const& [f, map] : decl2arg2funcs)
for (auto const& [t, new_def] : *map)
m_fmls.model_trail().hide(new_def);
vector<std::tuple<func_decl_ref, expr_ref, expr_dependency_ref>> defs;
for (auto const& [f, map] : decl2arg2funcs) {
expr * def = nullptr;
SASSERT(decl2args.contains(f));
bit_vector & bv = decl2args.find(f);
new_vars.reset();
new_args.reset();
for (unsigned i = 0; i < f->get_arity(); i++) {
new_vars.push_back(m.mk_var(i, f->get_domain(i)));
if (!bv.get(i))
new_args.push_back(new_vars.back());
}
for (auto const& [t, new_def] : *map) {
SASSERT(new_def->get_arity() == new_args.size());
app * new_t = m.mk_app(new_def, new_args);
if (def == nullptr) {
def = new_t;
}
else {
new_eqs.reset();
for (unsigned i = 0; i < f->get_arity(); i++)
if (bv.get(i))
new_eqs.push_back(m.mk_eq(new_vars.get(i), t->get_arg(i)));
SASSERT(new_eqs.size() > 0);
expr * cond = mk_and(m, new_eqs);
def = m.mk_ite(cond, new_t, def);
}
}
SASSERT(def);
expr_dependency* dep = nullptr;
defs.push_back({ func_decl_ref(f,m), expr_ref(def, m), expr_dependency_ref(dep, m) });
}
m_fmls.model_trail().push(defs, removed);
}
unsigned m_num_decls = 0;
public:
reduce_args_simplifier(ast_manager& m, dependent_expr_state& st, params_ref const& p) :
dependent_expr_simplifier(m, st),
m_bv(m)
{}
~reduce_args_simplifier() override {}
char const* name() const override { return "reduce-args"; }
void collect_statistics(statistics& st) const override {
st.update("reduced-funcs", m_num_decls);
}
void reset_statistics() override {
m_num_decls = 0;
}
void reduce() override {
m_fmls.freeze_suffix();
obj_hashtable<func_decl> non_candidates;
obj_map<func_decl, bit_vector> decl2args;
find_non_candidates(non_candidates);
populate_decl2args(non_candidates, decl2args);
if (decl2args.empty())
return;
m_num_decls += decl2args.size();
reduce_args_ctx ctx(m);
reduce_args_rw rw(*this, decl2args, ctx.m_decl2arg2funcs);
vector<dependent_expr> removed;
// if not global scope then what?
// cannot just use in incremental mode.
for (auto i : indices()) {
auto [f, p, d] = m_fmls[i]();
if (p)
continue;
expr_ref new_f(m);
rw(f, new_f);
if (f != new_f) {
removed.push_back(m_fmls[i]);
m_fmls.update(i, dependent_expr(m, new_f, p, d));
}
}
mk_mc(decl2args, ctx.m_decl2arg2funcs, removed);
}
};
dependent_expr_simplifier* mk_reduce_args_simplifier(ast_manager & m, dependent_expr_state& st, params_ref const & p) {
return alloc(reduce_args_simplifier, m, st, p);
}