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computing and memoizing info for regexes #4647

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merged 6 commits into from
Aug 19, 2020
Merged

computing and memoizing info for regexes #4647

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2ee2a68
computing and memoizing info for regex expressions
veanes Aug 18, 2020
94df0c1
computing and memoizing info for regex expressions
veanes Aug 18, 2020
5ab82a6
Merge branch 're-info' of https://github.com/veanes/z3 into re-info
veanes Aug 18, 2020
725d70c
took care of comments of the related pull request
veanes Aug 18, 2020
4265c24
removed +1 from min_length of ite
veanes Aug 18, 2020
98f09ee
added to_str method for re and fixed STRACE bug in get_info_rec
veanes Aug 19, 2020
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128 changes: 107 additions & 21 deletions src/ast/seq_decl_plugin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1312,28 +1312,9 @@ unsigned seq_util::str::max_length(expr* s) const {
return result;
}

unsigned seq_util::re::min_length(expr* r) const {
unsigned seq_util::re::min_length(expr* r) {
SASSERT(u.is_re(r));
expr* r1 = nullptr, *r2 = nullptr, *s = nullptr;
unsigned lo = 0, hi = 0;
if (is_empty(r))
return UINT_MAX;
if (is_concat(r, r1, r2))
return u.max_plus(min_length(r1), min_length(r2));
if (is_union(r, r1, r2) || m.is_ite(r, s, r1, r2))
return std::min(min_length(r1), min_length(r2));
if (is_intersection(r, r1, r2))
return std::max(min_length(r1), min_length(r2));
if (is_diff(r, r1, r2) || is_reverse(r, r1) || is_plus(r, r1))
return min_length(r1);
if (is_loop(r, r1, lo) || is_loop(r, r1, lo, hi))
return u.max_mul(lo, min_length(r1));
if (is_to_re(r, s))
return u.str.min_length(s);
if (is_range(r) || is_of_pred(r) || is_full_char(r))
return 1;
// Else: star, option, complement, full_seq, derivative
return 0;
return get_info(r).min_length;
}

unsigned seq_util::re::max_length(expr* r) const {
Expand Down Expand Up @@ -1595,3 +1576,108 @@ std::ostream& seq_util::re::pp::display(std::ostream& out) const {
// Else: derivative or is_of_pred
return out << mk_pp(e, re.m);
}

/*
Returns true iff info has been computed for the regex r
*/
bool seq_util::re::has_valid_info(expr* r) {
return r->get_id() < m_infos.size() && m_infos[r->get_id()].is_valid();
}

/*
Get the information value associated with the regular expression e
*/
seq_util::re::info seq_util::re::get_info(expr* e)
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Seems cleaner to separate the memoization from the recursive calls.

info get_info(expr * e) {
     auto result = get_cached_info(e);
     if (result.is_valid())
           return result;
     m_info_pinned.push_back(e);
     return get_info_rec(e);
}

info get_info_rec(expr* e) {
     auto result = get_cached_info(e);
     if (result.is_valid())
           return result;
     if (!is_app(e))
           return unknown_info;
     result = mk_info(to_app(e));
     add_cache(e, result);
     return result;
}

info mk_info(app* r) {
       if (r->get_family_id() == u.get_family_id()) {
            switch (r->get_decl_kind()) {
            case ...
            
            }
            return unknown_info;
       }
       if (m.is_ite(r, c, t, e)) {

       }
     
}

{
SASSERT(u.is_re(e));
if (!has_valid_info(e)) {
m_info_pinned.push_back(e);
compute_info_rec(e);
}
return m_infos[e->get_id()];
}

/*
Computes the info value for the given regex e recursively over the structure of e
*/
void seq_util::re::compute_info_rec(expr* e) {
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thus with return value a seq_util::re::info you can use the result in the combiner.

if (has_valid_info(e))
return;

SASSERT(is_app(e));
app* ea = to_app(e);
SASSERT(!m.is_ite(e));
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this is going to be too fragile to assume the expressions have some restricted form.

SASSERT(ea->get_decl()->get_decl_kind() != OP_RE_DERIVATIVE);
SASSERT(ea->get_decl()->get_decl_kind() != _OP_RE_ANTIMOROV_UNION);

info e_info(invalid_info);
unsigned k1, k2;
switch (ea->get_decl()->get_decl_kind())
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the get_decl_kind() can only be accessed after you have ensured the family_id() of the decl belongs to seq. So there has to be a test whether the ea->get_family_id() is right.

{
case OP_RE_EMPTY_SET:
e_info = info(UINT_MAX);
break;
case OP_RE_FULL_SEQ_SET:
case OP_RE_STAR:
case OP_RE_OPTION:
e_info = info(0);
break;
case OP_RE_RANGE:
case OP_RE_FULL_CHAR_SET:
case OP_RE_OF_PRED:
e_info = info(1);
break;
case OP_RE_CONCAT:
compute_info_rec(ea->get_arg(0));
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if you have this return an info, then you can combine many of the lines that first compute info, then access it.

compute_info_rec(ea->get_arg(1));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
k2 = m_infos[ea->get_arg(1)->get_id()].min_length;
e_info = info(u.max_plus(k1, k2));
break;
case OP_RE_UNION:
compute_info_rec(ea->get_arg(0));
compute_info_rec(ea->get_arg(1));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
k2 = m_infos[ea->get_arg(1)->get_id()].min_length;
e_info = info(std::min(k1, k2));
break;
case OP_RE_INTERSECT:
compute_info_rec(ea->get_arg(0));
compute_info_rec(ea->get_arg(1));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
k2 = m_infos[ea->get_arg(1)->get_id()].min_length;
e_info = info(std::max(k1, k2));
break;
case OP_SEQ_TO_RE:
e_info = info(u.str.min_length(ea->get_arg(0)));
break;
case OP_RE_REVERSE:
case OP_RE_PLUS:
compute_info_rec(ea->get_arg(0));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
e_info = info(k1);
break;
case OP_RE_COMPLEMENT:
compute_info_rec(ea->get_arg(0));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
e_info = info(k1 > 0 ? 0 : UINT_MAX);
break;
case OP_RE_LOOP:
compute_info_rec(ea->get_arg(0));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
e_info = info(u.max_mul(k1, ea->get_decl()->get_parameter(0).get_int()));
break;
case OP_RE_DIFF:
compute_info_rec(ea->get_arg(0));
compute_info_rec(ea->get_arg(1));
k1 = m_infos[ea->get_arg(0)->get_id()].min_length;
k2 = m_infos[ea->get_arg(1)->get_id()].min_length;
e_info = info(std::max(k1, k2 > 0 ? 0 : UINT_MAX));
break;
default:
break;
}
m_infos.setx(e->get_id(), e_info, invalid_info);

STRACE("re_info", tout << "compute_info(" << pp(u.re, e) << "): min_length=" << m_infos[e->get_id()].min_length << std::endl;);
}
22 changes: 18 additions & 4 deletions src/ast/seq_decl_plugin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -409,12 +409,27 @@ class seq_util {
};

class re {
struct info {
bool valid;
unsigned min_length;
info() : valid(false), min_length(0) {}
info(unsigned k) : valid(true), min_length(k) {}

bool is_valid() { return valid; }
};

seq_util& u;
ast_manager& m;
family_id m_fid;
vector<info> m_infos;
expr_ref_vector m_info_pinned;
info invalid_info;

bool has_valid_info(expr* r);
void compute_info_rec(expr* r);

public:
re(seq_util& u): u(u), m(u.m), m_fid(u.m_fid) {}
re(seq_util& u): u(u), m(u.m), m_fid(u.m_fid), m_info_pinned(u.m) {}

sort* mk_re(sort* seq) { parameter param(seq); return m.mk_sort(m_fid, RE_SORT, 1, &param); }
sort* to_seq(sort* re);
Expand Down Expand Up @@ -478,10 +493,11 @@ class seq_util {
bool is_loop(expr const* n, expr*& body, unsigned& lo) const;
bool is_loop(expr const* n, expr*& body, expr*& lo, expr*& hi) const;
bool is_loop(expr const* n, expr*& body, expr*& lo) const;
unsigned min_length(expr* r) const;
unsigned min_length(expr* r);
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declare m_info and m_pinned with "mutable", then we can keep the const qualifier, which is probably reasonable.

unsigned max_length(expr* r) const;
bool is_epsilon(expr* r) const;
app* mk_epsilon(sort* seq_sort);
info get_info(expr* r);

class pp {
seq_util::re& re;
Expand All @@ -495,7 +511,6 @@ class seq_util {
pp(seq_util::re& r, expr* e) : re(r), e(e) {}
std::ostream& display(std::ostream&) const;
};

};
str str;
re re;
Expand All @@ -511,7 +526,6 @@ class seq_util {
~seq_util() {}

family_id get_family_id() const { return m_fid; }

};

inline std::ostream& operator<<(std::ostream& out, seq_util::re::pp const & p) { return p.display(out); }
Expand Down