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## Summary Fixes a `psmt` (parallel SMT tactic) regression where the solver hangs to a wall-clock timeout instead of returning `unknown` on formulas whose root cube is genuinely undetermined by an incomplete theory. - **Originating discussion:** https://github.com/Z3Prover/bench/discussions/2735 - **Benchmark:** `iss-3044/bug-1.smt2` (from [Z3 issue #3044](https://github.com/Z3Prover/z3/issues/3044)) ```smt2 (declare-fun a (Int) Bool) (declare-fun b (Int) Bool) (assert (distinct a b)) (check-sat-using psmt) ``` ## Divergence The recorded oracle (expected) vs. current z3 (combined stdout+stderr, `-T:20`): ```diff -(incomplete (theory array)) -unknown +timeout ``` ## Root cause The rewritten parallel tactic (`src/solver/parallel_tactical.cpp`, introduced in #9824/#9825) hangs on this input. In the worker `run()` loop, every `l_undef` cube result was treated as if the per-cube **conflict limit** had been reached: the worker escalated the per-thread conflict budget (`update_max_thread_conflicts`) and re-checked / re-split the same cube. When the `l_undef` actually comes from **theory incompleteness** (here, the array theory cannot decide `(distinct a b)` over `Int -> Bool`) rather than the conflict limit, the verdict never changes, so the worker re-checks the same cube forever. Compounding this, the `batch_manager` state machine had **no terminal `unknown` state** — the only way to finish was for some worker to prove `sat`/`unsat`, which is impossible for a root-level theory-incomplete formula. The combination produced an infinite loop and a wall-clock timeout. The pre-rewrite parallel tactic avoided this: its `giveup()` detected reasons starting with `(incomplete` / `(sat.giveup`, reported a soft undef, and echoed the reason to `verbose_stream()`. ## Fix All changes are confined to `src/solver/parallel_tactical.cpp` (47 insertions, 4 deletions): 1. **Distinguish genuine incompleteness from conflict-limit exhaustion.** In the worker `l_undef` case, only `reason_unknown() == "max-conflicts-reached"` benefits from escalating the budget / splitting. For any other reason (incomplete theory, quantifiers, lambdas, resource limits, ...) re-checking is futile, so the worker records a sound `unknown` and stops working the branch. 2. **Add a terminal `is_unknown` batch-manager state** (`set_unknown`, `get_result() -> l_undef`, reason storage). It is a *soft* result: it does not cancel the other workers, and a definitive `sat`/`unsat` verdict from another branch may still override it (the `set_sat`/`set_unsat` guards now permit overriding `is_unknown`). All `set_unsat` call sites are global formula-unsat (core ⊆ assumptions, or independent of the tested backbone literal), so the override is sound; tree-closure unsat remains guarded by `is_running` and cannot fire because the undef leaf stays open. 3. **Restore the reason output.** The captured `reason_unknown` is propagated to the result goal and echoed to `verbose_stream()`, reproducing the `(incomplete (theory array))` line that the sequential path / old parallel tactic emitted. ## Validation Rebuilt the `./z3` checkout (`./configure && make -C build -j16`) and re-ran the benchmark with the freshly built binary using the same options the snapshot capture uses (`-T:20`, combined stdout+stderr): ``` $ z3 inputs/issues/iss-3044/bug-1.smt2 -T:20 (incomplete (theory array)) unknown ``` This matches the recorded `bug-1.expected.out` oracle **byte-for-byte**, and the benchmark now completes in ~0.5s (was: timeout). Verified stable across 8 consecutive runs. Basic `psmt` `sat`/`unsat` checks continue to produce correct results. Opened as a **draft** for human review. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> > Generated by [Fix a Z3 snapshot-regression divergence](https://github.com/Z3Prover/bench/actions/runs/28313246856) · 5.7K AIC · ⌖ 85.8 AIC · ⊞ 41.2K · [◷](https://github.com/search?q=repo%3AZ3Prover%2Fz3+%22gh-aw-workflow-id%3A+snapshot-regression-fixer%22&type=pullrequests) <!-- gh-aw-agentic-workflow: Fix a Z3 snapshot-regression divergence, engine: copilot, version: 1.0.60, model: claude-opus-4.8, id: 28313246856, workflow_id: snapshot-regression-fixer, run: https://github.com/Z3Prover/bench/actions/runs/28313246856 --> <!-- gh-aw-workflow-id: snapshot-regression-fixer --> <!-- gh-aw-workflow-call-id: Z3Prover/bench/snapshot-regression-fixer --> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> |
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| .. | ||
| assertions | ||
| check_logic.cpp | ||
| check_logic.h | ||
| check_sat_result.cpp | ||
| check_sat_result.h | ||
| CMakeLists.txt | ||
| combined_solver.cpp | ||
| combined_solver.h | ||
| combined_solver_params.pyg | ||
| mus.cpp | ||
| mus.h | ||
| parallel_params.pyg | ||
| parallel_tactical.cpp | ||
| parallel_tactical.h | ||
| preferred_value_propagator.h | ||
| progress_callback.h | ||
| simplifier_solver.cpp | ||
| simplifier_solver.h | ||
| slice_solver.cpp | ||
| slice_solver.h | ||
| smt_logics.cpp | ||
| smt_logics.h | ||
| solver.cpp | ||
| solver.h | ||
| solver2tactic.cpp | ||
| solver2tactic.h | ||
| solver_na2as.cpp | ||
| solver_na2as.h | ||
| solver_pool.cpp | ||
| solver_pool.h | ||
| solver_preprocess.cpp | ||
| solver_preprocess.h | ||
| tactic2solver.cpp | ||
| tactic2solver.h | ||