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fix bug in seq rewriter op_cache::find (#4509)

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* remove unneeded reverse case in derivative; placeholder for generalized lifted derivative

* experimental tweaks to RE rewriter to improve performance

* if-then-else lifting
(broken code -- preserving this commit in case this idea is useful later)

* if-then-else derivative optimizations: new approach templates

* implement if-then-else BDD normal form for derivatives
(code compiles but is still buggy)

* remove std::cout debugging for PR

* Revert "remove std::cout debugging for PR"

This reverts commit c7bdc44d31.

* debugging

* fix derivative interaction with reverse; add flags for left/right derivative and lifting over union/intersection

* remove debugging statements for PR

* Revert "remove debugging statements for PR"

This reverts commit 38e85a7288.

* revert some purely cosmetic changes from upstream; fix a bug

* revert unnecessary changes

* remove some redundant rewrites and add a new one for str.in_re(s, comp(r))

* add disabled rewrite for complement

* fix bug in op cache find (result was not saved)

* remove debugging std::cout for PR
This commit is contained in:
calebstanford-msr 2020-06-09 14:36:31 -04:00 • committed by GitHub
parent ec1e733ef2
commit 1fd567d1e9
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 99 additions and 28 deletions
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22
src/smt/seq_regex.cpp
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@ -146,7 +146,6 @@ namespace smt {
m_to_propagate.push_back(lit);
}
/**
* Propagate the atom (accept s i r)
*
@ -222,9 +221,9 @@ namespace smt {
// (accept s i R) & len(s) > i => (accept s (+ i 1) D(nth(s, i), R)) or conds
expr_ref d(m);
expr_ref head = th.mk_nth(s, i);
d = re().mk_derivative(m.mk_var(0, m.get_sort(head)), r);
d = derivative_wrapper(m.mk_var(0, m.get_sort(head)), r);
// timer tm;
rewrite(d);
// std::cout << d->get_id() << " " << tm.get_seconds() << "\n";
// if (tm.get_seconds() > 1)
// std::cout << d << "\n";
@ -351,6 +350,17 @@ namespace smt {
return r;
}
/*
Wrapper around the regex symbolic derivative from the rewriter.
Ensures that the derivative is written in a normalized BDD form
with optimizations for if-then-else expressions involving the head.
*/
expr_ref seq_regex::derivative_wrapper(expr* hd, expr* r) {
expr_ref result = expr_ref(re().mk_derivative(hd, r), m);
rewrite(result);
return result;
}
void seq_regex::propagate_eq(expr* r1, expr* r2) {
expr_ref r = symmetric_diff(r1, r2);
expr_ref emp(re().mk_empty(m.get_sort(r)), m);
@ -392,8 +402,7 @@ namespace smt {
literal null_lit = th.mk_literal(is_nullable);
expr_ref hd = mk_first(r);
expr_ref d(m);
d = re().mk_derivative(hd, r);
rewrite(d);
d = derivative_wrapper(hd, r);
literal_vector lits;
lits.push_back(~lit);
if (null_lit != false_literal)
@ -450,8 +459,7 @@ namespace smt {
th.add_axiom(~lit, ~th.mk_literal(is_nullable));
expr_ref hd = mk_first(r);
expr_ref d(m);
d = re().mk_derivative(hd, r);
rewrite(d);
d = derivative_wrapper(hd, r);
literal_vector lits;
expr_ref_pair_vector cofactors(m);
get_cofactors(d, cofactors);