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Fixes #4552. Fixes #4555. The SMT-LIB standard mandates that definitions
are kept when `:global-declarations` are enabled. Until now, CVC4 was
keeping track of the symbols of a definition correctly but lost the body
of the definition when the user context was popped. This commit fixes
the issue by adding a `global` parameter to
`SmtEngine::defineFunction()` and `SmtEngine::defineFunctionRec()`. If
that parameter is set, the definitions of functions are added at level 0
to `d_definedFunctions` and the lemmas for recursive function
definitions are kept in an additional list and asserted during each
`checkSat` call. The commit also updates new API, the commands, and the
parsers to reflect this change.
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Fixes #4576. ASan was reporting memory leaks because the skolem manager
was being destroyed after the attributes and zombies were already
cleaned up in the destructor of NodeManager. This commit changes the
destruction order to ensure that the skolem manager is destroyed before
the rest of the cleanup.
Note: this issue did not only make the benchmark in #4576 fail but
several tests in our regressions.
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Also includes some minor improvement to expand definitions in TheoryDatatypes leftover from the branch.
Adds 3 regressions using the option --dt-nested-rec.
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Fixes #4446. This commit fixes two issues related to the handling of
Boolean term variables:
Removing Boolean subterms and replacing them with a Boolean term
variable introduces an equality of the form (= v t) where v is the
Boolean term variable and t is the term. It is important that these
equalities do not get removed. This commit changes
Theory::isLegalElimination() to take this into account.
The incorrect model reported in the issue was caused by some of the
Boolean term variables not being assigned values by the SAT solver
when we decided that the benchmark is satisfiable. Our justification
heuristic (correctly) decided that it is enough to satisfy one of the
disjuncts in the assertion to satisfy the whole assertion. However,
the assignments that we received from the SAT solver restricted us to
pick a specific value for one of the Boolean constants:
Literal | Value | Expr
---------------------------------------------------------
'7 ' 0 c
'0 ' 1 true
'1 ' 0 false
'2 ' 0 (a BOOLEAN_TERM_VARIABLE_274)
'5 ' _ b
'3 ' 1 (a BOOLEAN_TERM_VARIABLE_277)
'4 ' _ BOOLEAN_TERM_VARIABLE_274
'6 ' 0 BOOLEAN_TERM_VARIABLE_277
This meant that we had to pick true for BOOLEAN_TERM_VARIABLE_274
but we picked false since we simply treated it as an unassigned
variable. In general, the justification heuristic handles embedded
skolems introduced by term removal first and asks the SAT solver to
decide on Boolean term variables. However, for some logics, such as
QF_AUFLIA, we use the justification heuristic not for decisions but
only to decide when to stop, so those decisions were not done. This
commit introduces a conservative fix that adds a check after
satsifying all the assertions that makes sure that the equalities
introduced for Boolean terms are satisfied as well. Due to the eager
treatment of Boolean term variables when we use the justification
heuristic also for decisions, it is likely that we don't really have
the problem in that case but it doesn't hurt to enable the fix. It is
also possible that this fix is only required with models but it is
definitely safer to just always enable it (there could be tricky
corner cases involving the theory combination between UF and Boolean
terms). Additionally, this commit changes the ITE-specific naming in
the justification heuristic to reflect more accurately that we are in
general dealing with skolems introduced by term removals and not only
due to ITE removal.
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Previously we were treating constructor/selector/tester symbols as arguments to the abduct-to-synthesize.
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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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Fixes #4476.
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Fixes #4225, fixes CVC4/cvc4-projects#159, fixes CVC4/cvc4-projects#157, fixes #4289, fixes #4483.
This makes it so that the main model-based instantiation algorithm is not applied to quantified formulas with universally quantified functions.
Identation changed in a FMF function, this was refactored to conform to guidelines, and further cleaned.
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Fixes #4367. We set the theoryof-mode depending on whether sharing is
enabled or not. However, we were checking whether sharing was enabled
before theory widening, leading to unexpected results. This commit moves
the check after widening the theories.
For the benchmark in the issue, setting the theoryof-mode before theory
widening lead to problems because of the following:
The main solver checks the condition for enabling term-based
theoryof-mode, decides not to do it because sharing is not enabled
Main solver adds UF to the logic
Main solver does a check-sat all
Unsat core check runs, sees both UF and NRA enabled, and switches
to term-based mode
Main solver gets to second check-sat call, now the theoryof-mode is
suddenly changed, which leads to problems in the equality engine
This commit fixes the issue in this particular instance but it is important
to note that it does not address the issue of the subsolver changing
settings in general. This can only really be solved by separating the
options from the ExprManager/NodeManager and having separate
options for each SmtEngine/Solver instance.
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Fixes #4477. Logic ALL includes higher-order but we currently do not
support solving higher-order problems unless --uf-ho is enabled. This
commit changes the condition under which we parse -> and lambda to
only enabled parsing of those symbols if the logic allows higher-order
constraints and --uf-ho is enabled.
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Fixes #4525. The actual problem in the issue is not that the unsat core
is satisfiable but that our unsat core check is not working as intended.
Our unsat core check uses the same `ExprManager` as the main `SmtEngine`
and thus also shares the same attributes for nodes. However, since we
have a different `SmtEngine` instance for the check, we also have
different instances of `TheoryArith`. This leads to the check failing
due to the following:
- Our only input assertion is `(> (cot 0.0) (/ 1 0)))`.
- `TheoryArith::expandDefinition()` gets called on `(> (cot 0.0) (/ 1
0))` but nothing happens.
- `TheoryArith::expandDefinition()` gets called on `(/ 1 0)`, which gets
expanded as expected but no attribute is set because it happens in a
simple `TheoryArith::eliminateOperators()` call.
- `TheoryArith::expandDefinition()` on `(cot (/ 0 1))` first expands to
`(/ 1 0)` (not cached) and then we expand it recursively to the
expected term and cache `(/ 1 0) ---> (ite (= 0 0) (divByZero 1.0) (/
1 0))`.
Up to this point, things are suboptimal but there are no correctness
issues. The problem starts when we do the same process in the unsat core
check:
- Our only input assertion is again `(> (cot 0.0) (/ 1 0)))`.
- `TheoryArith::expandDefinition()` gets called on `(> (cot 0.0) (/ 1
0))` but nothing happens.
- `TheoryArith::expandDefinition()` gets called on `(/ 1 0)`, which gets
expanded as expected but no attribute is set or checked because it
happens in a simple `TheoryArith::eliminateOperators()` call. Note
that the skolem introduced here for the division-by-zero case is
different from the skolem introduced above because this is in a
different `TheoryArith` instance that does not know the existing
skolems.
- `TheoryArith::expandDefinition()` on `(cot (/ 0 1))` first expands to
`(/ 1 0)` (not cached) and then we use the cache from our solving call
to expand it `(/ 1 0) ---> (ite (= 0 0) (divByZero 1.0) (/ 1 0))`.
Note that `divByZero` here is the skolem from the main solver.
As a result, the preprocessed assertions mix skolems from the main
`SmtEngine` with the `SmtEngine` of the unsat core check, making the
constraints satisfiable.
To solve this problem, this commit removes the caching-by-attribute
mechanism. The reason for removing it is that it is currently
ineffective (since most eliminations do not seem to be cached) and there
are caches at other levels, e.g. when expanding definitions. If we deem
the operator elimination to be a bottleneck, we can introduce a similar
mechanism at the level of `TheoryArith`.
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This error is a bit inexplicable but very very definitely wrong.
A test case from the original bug report is included.
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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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This introduces a rewrite based on regular expression inclusion (using calls to the RegExpEntail utility function).
This allows us to justify the regular expression inclusion inference as a rewrite.
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Fixes #4482.
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This adds a new inference schema to strings that was discovered by the internal proof checker. It says that we are in conflict when an equality between the normal forms of two terms in the same equivalence class rewrites to false.
It also improves the efficiency of processing normal forms by only considering normal forms that are unique up to rewriting.
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A bug was introduced when adding the Node-level datatype implementation in d803e7f. The code did not probably get the arity of a sort constructor. This adds TypeNode::getSortConstructorArity and uses it during parametric datatype type resolution.
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When we eliminate a variable x -> v during simplification, it may be the case that v contains "unevaluated" operators like forall, choice, etc. Thus, we do not produce correct models for such inputs unless simplification is disabled.
This PR ensures we only eliminate variables when v contains only evaluated operators.
Additionally, the kinds registered as unevaluated were slightly modified so that when we are in a logic like QF_LIA, there are no registered unevaluated operators, hence the check above is unnecessary. This is to minimize the performance impact of this change.
Fixes #4500.
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Fixes an issue with over-pruning in SyGuS where using multiple sygus types that map to the same builtin type. Our mapping sygusToBuiltin did not ensure that free variables were unique.
Fixes #4383.
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Renamed operator CHOICE to WITNESS, and removed it from the front end
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Fixes #3692 and an assertion failure that came up during the test runs
for SMT-COMP. The bit-vector rewrites `SolveEq` and
`PlusCombineLikeTerms` were not always idempotent. At a high level,
`SolveEq` combines common terms from two sides of an equality and
`PlusCombineLikeTerms` combines common terms within an addition.
However, in doing so, these rewrites were reordering the operands of the
bit-vector addition based on the node ids of the terms that were
multiplied with their coefficients. Consider the addition `3 * x * y + 5
* y * z` (the bit-width does not matter). `PlusCombineLikeTerms` would
reorder this addition to `5 * y * z + 3 * x * y` if the node id of `y *
z` was smaller than the node id of `x * y`. The issue is that node ids
are not fixed for a given term: If we have a term `x * y` and that term
reaches ref count 0, we may get a different id for that same term if we
recreate it later on. When terms reach ref count 0, we don't immediately
delete them but add them to our set of zombies to be deleted whenever
the list of zombies grows larger than some fixed size. When applying
`SolveEq` and `PlusCombineLikeTerms` multiple times (even in direct
succession without doing anything else), the node order may change
because some of the terms like `x * y` may be zombies while others have
been deleted and get new ids, leading to the relative order of node ids
changing. I suspect that we could construct a case where we get into an
infinite rewrite loop.
This commit addresses the issue as follows: It does not perform the
rewrites `SolveEq` and `PlusCombineLikeTerms` if none of the operands
change. This makes the rewrites idempotent. Note however that we are
still not guaranteeing that a term has the same rewritten form
throughout an execution because the node ids may change if the term has
been freed in the meantime. However, this limitation is consistent with
other rewrites such as the reordering of equalities.
I am including the minimized test case from our run on SMT-LIB. I am
ommittin the test case from #3692 because I couldn't trigger it on
master (not surprising since the issue requires very specific
circumstances to actually occur). However, I was able to reproduce the
issue on the CVC4 version mentioned in the issue and confirmed that this
fix worked for that older version.
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Fixes an unsoundness in unconstrained simplification, fixes #4469.
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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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(#4415)
An incorrect answer of "sat" could be found after 8 seconds on the given benchmark (with --strings-fmf) due to a circular justification for why an extended function was reduced. In particular, we ran checkExtfInference on the same term twice and then marked it as reduced since we had already seen it. This makes the code more conservative.
Notice I'm making the code doubly conservative in case there is any chance for duplication again (e.g. if ExtTheory provides duplicate terms).
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This updates the default cardinality in strings to match the Unicode standard, 196608.
This avoids a check-model failure from 25 benchmarks in SMT-LIB, which were related to a split due to insufficient constants being required during collectModelInfo.
This also makes a few places throw an AlwaysAssert(false) that otherwise would lead to incorrect models. These regardless should never throw, but it would be better to have an assertion failure.
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Fixes #4391.
The sets cardinality cycle rule is analogous to the S-Cycle rule for strings (see Liang et al CAV 2014). This rule is typically never applied but can be applied in rare cases where theory combination does not determine a correct arrangement of equalities over sets terms that is consistent with the arithmetic arrangement of their cardinalities at full effort. Notice the regression from #4391 has non-linear arithmetic, (mod 0 d), which is translated to UF.
The cardinality cycle rule had a bug: it assumed that cycles that were encountered were loops e1 = e2 = ... = e1 but in general they can be lassos e1 = ... = e2 = ... = e2. This ensures the Venn region cycle e2 = ... = e2 is the conclusion in this case, instead of unsoundly concluding e1 = ... = e2.
Strings does not have a similar issue:
https://github.com/CVC4/CVC4/blob/master/src/theory/strings/core_solver.cpp#L488
Here, when a cycle is encountered, it is processed at the point in traversal where the loop is closed.
This is not critical for SMT-COMP but should be in the 1.8 release.
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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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Fixes #4376. Commit 6255c0356bd78140a9cf075491c1d4608ac27704 removed
support for conjunctions in the conclusion of facts. However,
`F_ENDPOINT_EMP` generates a conjunction in the conclusion of the
inference if multiple components are inferred to be empty. This commit
reinstantiates support for conjunctions in the conclusion of facts.
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conflict-based instantiation (#4280)
Conflict-based instantiation would sometimes initialize a match x -> getRepresentative(t) when a quantified formula contained x = t. This leads to issues where getRepresentative(t) is an illegal term (say, in combination with CEGQI). This makes it so the representative is accessed when necessary instead of being set as part of the match.
Fixes #4275.
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Fixes #4277.
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Fixes #4243.
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Fixes #4290 and fixes #4292.
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This adds a fix to ensure dump-unsat-cores-full works by modifying the public options function. This options currently does not work since dumpUnsatCores is only set internally now. This fix is only required until options are refactored so that SmtEngine owns the authoritative copy of options.
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A recent change made it so that defined functions would print as the anonymous lambda corresponding to their definition if the SyGuS v1 parser was used. This was caused by comparison with the wrong kind in the new API.
Notice that the v2 parser does not have this issue.
This also adds a regression to ensure this behavior is maintained by the SyGuS v2 parser.
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Fixes #4273 and fixes #4274 .
This also removes a spurious assertion from the Node::substitute method that the result node is not equal to the domain. This is violated for f(f(x)) { f(x) -> x }.
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Should fix nightlies.
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Previously we were doing rewriting/expand definitions during grammar normalization, which overwrote the original sygus operators. The connection to the original grammar was maintained via the SygusPrintCallback utility, which ensured that a sygus term printed in a way that matched the grammar.
We now have several use cases where solutions from SyGuS will be directly exported to the user, including the current use of get-abduct. This means that the terms must match the grammar, and we cannot simply rely on the print callback.
This moves the code to normalize sygus operators to datatypes utils, where the conversion between sygus and builtin terms takes place. This allows a version of this function where isExternal = true, which constructs terms matching the original grammar.
This PR enables the SyGuS API to have an accurate getSynthSolution method. It also will eliminate the need for SygusPrintCallback altogether, once the v1 parser is deleted.
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A regress2 SyGuS benchmark is taking 110 seconds in production on my machine. This was likely caused by the recent update v1 -> v2, which impacts the internal representation and hence the search. Disabling for now.
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This PR enables THEORY_UF by default for sets and adds the operator CHOOSE for sets which returns an element from a given set. The semantics is as follows:
If a set A = {x}, then the term (choose A) is equivalent to the term x.
If the set is empty, then (choose A) is an arbitrary value.
If the set has cardinality > 1, then (choose A) will deterministically return an element in A.
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Fixes #3971 and fixes #3991. In incremental mode, the logic can change from one
(check-sat) call to another. In the reported issue, we start with QF_NIA
but then switch to QF_UFNIA because there is a div term (which has a UF in
its expanded form). Dealing with this issue is challenging in general. As a
result, we have decided not to allow theory widening in
Theory::expandDefinitions() anymore but instead to do it eagerly in
SmtEngine::setDefaults().
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A recent commit (45e489e) made it so that dump-models did not automatically enable produce-models in the global options object, but instead the SmtEngine enabled produce-models internally. The code for dump-models and dump-proofs was (perhaps out of paranoia) checking produce-models and produce-proofs. This removes this check, which is the correct thing to do since SmtEngine internally ensures produce-models is set.
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Benchmark recently became slow, disable for now.
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Fixes #4170.
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Towards support for the strings standard.
Adds support to (_ char #x ... ) syntax for characters.
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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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Added the operator choice to Smt2.g and Cvc.g.
Removed the unused parameter hasBoundVars from TheoryModel::getModelValue
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Fixes #4151. Commit e9f4cec2cad02e270747759223090c16b9d2d44c fixed how
`(reset-assertions)` is handled by destroying and recreating the
`PropEngine` owned by `SmtEngine`. When unsat cores are enabled,
creating a `PropEngine` triggers the creation of a SAT proof and a CNF
proof. In the `ProofManager`, we had assertions that checked that those
kinds of proofs were only created once, which is not true anymore. This
commit removes the assertions, cleans up the memory management in
`ProofManager` to use `std::unique_ptr` and makes all the
`ProofManager::init*` methods non-static for consistency.
The commit also fixes an additional issue that I encountered while
testing the fix: When creating the new `PropEngine`, we were not
asserting `true` and `(not false)`, which lead to an error if we tried
to get the unsat core after a `(reset-assertion)` command and we had
asserted `(assert false)`. The commit fixes this by asserting `true` and
`(not false)` in the constructor of `PropEngine`.
The regression test is an extension of the example in #4151 and covers
both issues.
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