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## Problem Fixes #10133. For `QF_BV` with `parallel.enable=true`, the solver could return `sat` with a model that violates its own assertions. `mk_qfbv_tactic` routes SAT solving to `mk_psat_tactic`, which built the solver via `mk_inc_sat_solver(m, p, false)` (non-incremental). The parallel cube-and-conquer engine **reuses this single solver** across many `check_sat(cube)` calls, but SAT variable/blocked-clause elimination ran because the simplifier's incremental gate was disabled. Elimination model reconstruction is only sound for a single one-shot solve; under repeated cube assumptions it produces models where eliminated Tseitin variables get values contradicting the original clauses. ## Root cause (two coupled defects) 1. **Stale simplifier cache.** `inc_sat_solver`'s constructor called `m_solver.set_incremental()` *after* `updt_params()`. The SAT simplifier caches `m_incremental_mode` from the SAT config *during* `updt_params`, so setting the incremental flag afterwards left a stale non-incremental mode and elimination stayed enabled. (This is why simply passing `incremental_mode=true` had no effect on its own.) 2. **Non-incremental parallel solver.** `mk_psat_tactic` created the reused solver as non-incremental. ## Fix - Move `set_incremental()` **before** `updt_params()` in the `inc_sat_solver` constructor so the simplifier caches the correct mode. - Create the parallel solver with `incremental_mode=true` in `mk_psat_tactic`. ## Validation - Variable elimination on the QF_BV parallel path drops to zero (`sat-elim-bool-vars-res` 21664 -> 0); remaining `elim-clauses/literals` are sound cleaner/subsumption steps. - Consistent with ground truth: on 4.16.0, `sat.elim_vars=false` removed all 7 `failed to verify` errors; this change disables exactly that unsound elimination, scoped to the reused/parallel solver. - A solvable QF_BV instance returns a **valid** model under `parallel.enable=true model_validate=true`. - All 92 unit tests pass (`test-z3 /a`). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> |
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| .. | ||
| CMakeLists.txt | ||
| inc_sat_solver.cpp | ||
| inc_sat_solver.h | ||
| sat_smt_setup.h | ||
| sat_smt_solver.cpp | ||
| sat_smt_solver.h | ||