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This unifies top-level substitutions and theory model substitutions. Env is now passed to the TheoryModel, which has access to top-level substitutions.
The former was used for simplfying assertions in the preprocessor, the latter was used for evaluating terms in the model.
There is no reason to have these two things be separate.
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This makes it so that we attempt evaluation + rewriting on applications of operators that do not always evaluate, and return constants in case the evaluation was successful.
This fixes warnings for check-models on 43 of our regressions, and also uncovered one regression where our model was wrong but check-models silently succeeded. I've opened CVC4/cvc4-projects#276 for fixing the latter.
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Adds 3 of the 6 benchmarks from issue 6214, the 1st and 5th benchmarks timeout.
Fixes #6214.
These benchmarks were fixed by 3c98bb2.
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Fixes #4179.
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Fixes #6271.
This was triggered by recent fixes, this fixes solution soundness issues with symbolic regular expressions due to spuriously included antecedants, which made lemmas SAT-context dependent while being cached as user-context dependent.
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Fixes the first benchmark from #6203.
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This ensures that we always cache regular expressions in a user-dependent manner. Previously, we were erroneously caching in a SAT-dependent way for very rare cases when non-constant regular expressions were used. Since we never dependent on current assertions for the unfolding, there is no need to cache in the SAT context.
This fixes the second benchmark from #6203.
This PR also improves our traces for checking models in strings.
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In rare cases, we may reuse skolems for different terms (those that are the same up to purification) due to recent changes in how skolem are generated. This guards for this case in the term formula remover, which avoids assertion failures in cd insert hash map.
Fixes #6132.
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String terms may enter into the equality engine without appearing in assertions, due to eager context-dependent simplification internal to the equality engine (--strings-eager-eval). In rare cases, we did not catch when a new string constant appeared in the equality engine, meaning it would not be marked as relevant leading to bogus models in incremental mode.
This makes it so that proxy variables are stored in a user-context dependent manner, which impacts when terms marked as having a proxy variable are registered.
The PR also simplifies our policies for when string terms are registered slightly.
Fixes #6072.
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This commit refactors the run_regression.py script and adds options for enabling/disabling checking of proofs and unsat cores. Both options are enabled by default and disabled for each corresponding CI build.
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This is so that we can use CI in master for proofs.
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Fixes #6142.
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Fixes #6075.
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This fixes two issues for preprocessing:
(1) The term preregistration visitor was calling preRegister on terms multiple times in a SAT context, which the linear arithmetic solver is sensitive to.
(2) It was possible for non-preprocessed terms to appear in assertions if they were on the RHS of substitutions learned by non-clausal simplification, and substituted into assertions post-theory-preprocessing.
To fix (1), the SharedTermsVisitor is update to track which theories has preregistered each term, as is done in the PreRegisterVisitor. To fix (2), we no longer apply-subst after theory preprocessing.
These two fixes are required to fix #6071.
Note: we should performance test this on SMT-LIB.
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This commit removes parser and printer support for old SMT-LIB standards and also converts all regression tests to 2.6.
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Previously, it was optional whether to put length constraints in conclusion for deq string inferences. However, due to optimizations in skolem caching, it is now required to guard these length constraints.
It furthermore changes the policy to not ignore the lengths for the registered skolem, since it may be shared elsewhere.
Fixes #5940.
Notice that proof-new already requires this option to be enabled when proofs are enabled. Hence, this will simplify proof-new when merged.
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This PR simplifies our heuristic for inferring when an explanation for a strings lemma can be minimized based on proxy variable definitions. In particular, we do not turn solved equalities for proxy variables into substitutions. This aspect of the heuristic is incompatible with the new eager solver work, and moreover is buggy since substitutions should not be applied within string terms. The latter was leading the incorrect models on the 2 issues fixed by this PR.
Current results on the eager solver on SMT-LIB shows this change has very little performance impact.
Fixes #5692, fixes #5610.
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This option eliminates extended functions in strings eagerly. This was incorrectly done at ppRewrite previously, which should not add lemmas. Instead, this makes this technique into a preprocessing pass. To do this, the interface for the strings preprocessor was cleaned to have fewer dependencies, and made to track a cache internally.
Fixes #5608, fixes #5745, fixes #5767, fixes #5771, fixes #5406.
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There is an assumption that is not guaranteed to hold in this rule, thus we should not try to explain in the equality engine.
Fixes #5611.
Note this inference was not previously covered in our coverage build.
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We can close #5520, we can close #5378.
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The issue was caused by simple regular expression consume being too aggressive when a recursive call was made to the method. In particular, we were assuming that the body of the star must be unrolled to fully consume a string, when it can be skipped if we are not at top level.
Fixes #5510.
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Leads to free variables in assertions when using `str.<=` whose reduction uses EXISTS not FORALL.
Fixes #5483.
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Fixes #5330. The issue mentions to related model checking failures:
When the theory of strings computes a model, there is a step that
chooses a constant that is different from other constants of the same
length in other equivalence classes. In the example, the issue was
that the constant "A" was introduced by doing evaluation in the
equality engine of the theory of strings. The constant was then not
added to the term set and was skipped while asserting the equality
engine to the theory model. As a result, an equivalence class was
assigned "A" even though it already existed, which made the model
invalid. The fix ensures that all constants in the equality engine are
added to the theory model. It should be ok to handle the issue during
model construction because other theories shouldn't have to care about
the constants that we computed internally within the theory of
strings.
When an equivalence class has a normal form that consists of a single
seq.unit, then we need to make sure that the value for the argument
is consistent with the rest of the model and we have to make sure that
we choose different values for different equivalence classes. The
commit adds code for retrieving the value of the argument to
seq.unit from the model and adds the resulting constant to the
theory model to block it for other equivalence classes. Previously,
this was not done and we ended up with two different equivalence
classes being assigned the same constant.
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This makes strings proxy variables map to be context-independent. They should be context independent since we are using attributes to mark proxy variables, which are context-independent. This led to the crash reported on #5374 since proxy variables would persist across multiple user contexts, but would be missing in the user-context dependent map.
This fixes #5374.
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Fixes #4915. Previously, `str.substr` did not require `--strings-exp`.
However, when `--strings-exp` is not active, we do not send terms to the
extended solver for registration, which meant that `str.substr` was
never reduced. This commit adds `str.substr` to the operators that
require `--strings-exp`.
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Fixes #4701. That benchmark now times out.
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Fixes #4759 .
Also refactors this method.
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Commit 64a7db86206aa0993f75446a3e7f77f3c0c023c6 introduced a caching
mechanism in `TheoryEngine::getExplanation()`. However, there seem to be
issues related to the timestamps of the explanations. This commit fixes
the issue by making the timestamp part of the cache. The change ensures
that explanations for a certain node never rely on other explanations
for that node with a later timestamp.
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This adds basic support for string/sequence updating, which has a semantics that is length preserving.
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The RE derive inference was not designed to handle re.comp. This makes the application of this inference more conservative.
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Fixes #4437.
This is a simpler fix that aborts the preprocessing pass when a quantifier is encountered.
It also updates our smt2 parser to throw a logic exception when forall/exists is used in non-quantified logics. This is required to ensure that unconstrained simplification does not throw an exception to a user as a result of accidentally setting the wrong logic.
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This is a major refactor of how operators are eliminated in arithmetic. Currently there were (at least) two things wrong:
(1) ppRewriteTerm sent lemmas on the output channel. This behavior is incompatible with how preprocessing works. In particular, this caused unconstrained simplification to be unaware of terms from such lemmas, leading to incorrect "sat" answers.
(2) Lemmas used to eliminate certain "div-like" terms were processed in a context-independent way. However, lemmas should be cached in a user-context-dependent way. This was leading to incorrect "sat" answers in incremental.
The solution to these issues is to eliminate operators via the construction of witness terms. No lemmas are sent out, and instead these lemmas are the consequence of term formula removal in the standard way.
As a result of the refactor, 2 quantifiers regressions time out due to infinite branch and bound issues (one only during --check-unsat-cores). These appear to be random and I've changed the options to avoid these issues. 3 others now have check-model warnings, which I've added --quiet to. Improving check-model will be addressed on a future PR.
This PR is not required for SMT COMP since we have workarounds that avoid both the incorrect behaviors in our scripts.
Also notice that --rewrite-divk is effectively now enabled by default always.
Fixes #4484, fixes #4486, fixes #4481.
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Disabling re-elim performs better overall in many recent experiments.
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Fixes regress1.
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This fixes a soundness issue in strings caused by an incorrect skolem share.
This adds a regression that corresponds to the rewrite that this skolem share was justified by, which is "sat" (the rewrite does not hold). This benchmark in fact was answered "unsat" by CVC4 prior to this PR.
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Fixes nightlies.
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This PR merges --lang=smt2.6.1 and --lang=smt2.6 (default). It makes it so that 2.6 always expects the syntax of the string standard http://smtlib.cs.uiowa.edu/theories-UnicodeStrings.shtml.
I've updated the regressions so that the 2.6 benchmarks are now compliant with the standard. Some of the <=2.5 benchmarks I've updated to 2.6. Others I have left for now, in particular the ones that rely on special characters or ad-hoc escape sequences. The old formats will be supported in the release but removed shortly afterwards.
This PR is a prerequisite for the release, but not necessarily SMT-COMP (which will use --lang=smt2.6.1 if needed). Notice that we still do not have parsing support for str.replace_re or str.replace_re_all. This is required to be fully compliant.
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Fixes #4379. This was caused by a splitting lemma rewriting to a conjunction, being processed as a fact, and having a pending phase requirement sent out assuming the inference was to be processed as a lemma. This forces 2 of the splits in the core solver to be always processed as lemmas.
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Towards support for the strings standard.
This modifies our interface so that we accept the SMT-LIB standard versions of re.loop and re.^. This means re.loop no longer accepts 3 arguments but 1 (with 2 indices).
This means we no longer accept re.loop with only a lower bound and no upper bound on the number of repetitions.
Also fixes #4161.
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Fixes #3408 .
Adds basic rewriter, parsing, type checking and implements the required cases in regexp_operation.cpp. It also adds some missing documentation in regexp_operation.h
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Type rules, parsing and printing, basic rewriting including constant evaluation, reduction for string reverse (`str.rev`).
Also improves support in a few places for tolower/toupper.
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This fixes a corner case of the str-to-int reduction for the case where the argument is the empty string.
This fixes #3357.
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Fixes #3272.
This was caused by not explaining the last equal component in a flat form inference. For example, if `x=y`, we may infer `z=""` from `u++x++z=u++y` since the 1st and 2nd components of these strings are equal. However, we would not add the explanation of `x=y` due to an off-by-one error.
Notice that this code is very rarely used (the code for F_EndpointEmp is not covered by our regressions). This is since length elaboration should catch conflicting cases like above, where `len(u++x++z)!=len(u++y)` if `x=y` and `z!=""` and thus `u++x++z != u++y`. #3272 happened to catch a rare case where it is applied. This is likely due to theory combination not propagating an equality prior to running a full effort call to strings check, which is unexpected but not impossible.
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constant (#3218)
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