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https://github.com/Z3Prover/z3
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03a76c0309
ZIPT review identified two hot-path inefficiencies in `euf_sgraph`:
`drop_left`/`drop_right` were implemented as repeated single-token drops
(`O(count × depth)`), and `classify` performed redundant string checks.
This change aligns behavior with the intended tree-navigation approach
while keeping semantics unchanged.
- **Algorithmic update: `drop_left` / `drop_right`**
- Replaced iterative `drop_first`/`drop_last` loops with direct
recursion over concat children.
- New logic drops across subtree boundaries using child lengths,
reducing work to tree depth (`O(depth)`).
- **Classification cleanup: `classify`**
- Collapsed double `is_string` probing into a single `is_string(e, s)`
call.
- Preserves existing kind mapping (`empty` vs non-empty string constant
handling).
- **Focused test coverage extension**
- Added boundary checks in `test_sgraph_drop` for `drop_left(..., 1)`
and `drop_right(..., 1)` on a 4-token concat tree.
```cpp
snode* sgraph::drop_left(snode* n, unsigned count) {
if (count == 0 || n->is_empty()) return n;
if (count >= n->length()) return mk_empty_seq(n->get_sort());
SASSERT(n->is_concat());
unsigned left_len = n->arg(0)->length();
if (count < left_len)
return mk_concat(drop_left(n->arg(0), count), n->arg(1));
return drop_left(n->arg(1), count - left_len);
}
```
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
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| .. | ||
| ackermannization | ||
| api | ||
| ast | ||
| cmd_context | ||
| math | ||
| model | ||
| muz | ||
| nlsat | ||
| opt | ||
| params | ||
| parsers | ||
| qe | ||
| sat | ||
| shell | ||
| smt | ||
| solver | ||
| tactic | ||
| test | ||
| util | ||
| CMakeLists.txt | ||