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Let's try to justify bounds

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This commit is contained in:
CEisenhofer 2026-04-20 15:52:35 +02:00
parent 0bcdca787f
commit 41412293fe
5 changed files with 246 additions and 65 deletions
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17
src/smt/seq/seq_parikh.cpp
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@ -249,7 +249,8 @@ namespace seq {
//
// This check is lightweight — it uses only modular arithmetic on the already-
// known regex min/max lengths and the per-variable bounds stored in the node.
str_mem const* seq_parikh::check_parikh_conflict(nielsen_node& node) {
str_mem const* seq_parikh::check_parikh_conflict(nielsen_node& node, dep_tracker& dep) {
dep = nullptr;
for (str_mem const& mem : node.str_mems()) {
if (!mem.m_str || !mem.m_regex || !mem.m_str->is_var())
continue;
@ -269,9 +270,15 @@ namespace seq {
SASSERT(stride > 1);
rational lb_r, ub_r;
if (!node.lower_bound(mem.m_str->get_expr(), lb_r) || !node.upper_bound(mem.m_str->get_expr(), ub_r))
dep_tracker lb_dep = nullptr;
dep_tracker ub_dep = nullptr;
if (!node.lower_bound(mem.m_str->get_expr(), lb_r, lb_dep) ||
!node.upper_bound(mem.m_str->get_expr(), ub_r, ub_dep))
continue;
dep_tracker cur_dep = node.graph().dep_mgr().mk_join(mem.m_dep, lb_dep);
cur_dep = node.graph().dep_mgr().mk_join(cur_dep, ub_dep);
SASSERT(lb_r <= ub_r);
if (ub_r > INT_MAX)
continue;
@ -294,6 +301,7 @@ namespace seq {
// In that case k_min would be huge, and min_len + stride*k_min would
// also overflow ub → treat as a conflict immediately.
if (gap > UINT_MAX - (stride - 1)) {
dep = cur_dep;
return &mem; // ceiling division would overflow → k_min too large
}
k_min = (gap + stride - 1) / stride;
@ -303,12 +311,15 @@ namespace seq {
unsigned len_at_k_min;
if (k_min > (UINT_MAX - min_len) / stride) {
// Overflow: min_len + stride * k_min > UINT_MAX ≥ ub → conflict.
dep = cur_dep;
return &mem;
}
len_at_k_min = min_len + stride * k_min;
if (ub != UINT_MAX && len_at_k_min > ub)
if (ub != UINT_MAX && len_at_k_min > ub) {
dep = cur_dep;
return &mem; // no valid k exists → Parikh conflict
}
}
return nullptr;
}