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* Removes incremental API check (#3011)
* Fixes toSatValueLit to use the new semantics of CaDiCaL's val()
Fixes #3011
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* improved proof production statistics
This commit creates new statistics which will help us understand what is
so expensive about proof production.
There are already statistics for:
* Net time spent building/printing the LFSC proof.
* Size of the LFSC proof.
This commit adds statistics for:
* The time cost of DRAT optimization:
* net time
* tool time (drat-trim)
* clause matching time (matching core clauses with input clauses)
* Non-trivial because drat-trim can (and does) dedup and reorder
literals
* The advantage of DRAT optimization (proof/formula size before/after)
* The time cost of DRAT translation [to LRAT or ER] (net time, tool time)
* The time cost of skeleton traversal
* The time cost of printing declatations
* The time cost of printing CNF proofs
* The time cost of printing theory lemmas
* The time cost of printing final UNSAT proof.
There is a method, toStream, which is responsible for much of proof
production. The whole method was timed, but subsections were not. The
timings above consider subsections of it.
I also wanted to better understand the cost of DRAT optimization and
translation.
* [BV Proof] Optimize DRAT optimization
tldr: I made a bad data-structure/algorithm choice when implementing
part of DRAT/CNF-optimization, which consumed **a lot** of time on some
bechmarks. This commit fixes that choice.
Long Version:
Set-Keyed Maps Considered Harmful
=================================
Algorithmic Problem
-------------------
The DRAT optimization process spits out a unsatifiable core of the CNF.
The clauses in the core are all from the original formula, but their
literals may have been reordered and deduplicated. We must match the
old clauses with new ones, so we know which old clauses are in the core.
Old (BAD) Solution
------------------
Before I didn't really think about this process very much. I built a
solution in which clauses were canonically represented by hash sets of
literals, and made a hash map from canonical clauses to clause indices
into the original CNF.
Problem With Old Solution
-------------------------
In hindsight this was a bad idea. First, it required a new hash set to
be heap-allocated for every clause in the CNF. Second, the map lookups
required set-hashes (reasonable -- linear time, once) and hash-set
equality (not reasonable -- quadratic time, multiple times) on every
lookup.
New Solution
------------
The ideal solution is probably to have the map from clauses to clause
ids be something like a trie. STL doesn't have a trie, but representing
clauses as sorted, deduped vectors of literal in a tree based on
lexicographical comparison is pretty closed to this. On randomly chosen
examples it seems to be a huge improvement over the old
map-keyed-by-sets solution, and I'm in the process of running a full set
of bechmarks.
Also, we store pointers to the clauses already stored elsewhere in the
proof, instead of allocating new memory for them.
Future Work
-----------
It may also be reasonable to do a hash map of sorted, deduped, vector
clauses. I haven't tried this, yet (there's a TODO in the code).
* Update src/proof/clausal_bitvector_proof.h
Thanks andres!
Co-Authored-By: Andres Noetzli <andres.noetzli@gmail.com>
* Respond to Andres' Review: better use of CodeTimer
* Removed commented code (Andres)
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This commit adds support for eager bit-blasting with CaDiCaL on
incremental benchmarks. Since not all CaDiCaL versions support
incremental solving, the commit adds a CMake check that checks whether
`CaDiCaL::Solver::assume()` exists.
Note: The check uses `check_cxx_source_compiles`, which is not very
elegant but I could not find a better solution (e.g.
`check_cxx_symbol_exists()` does not seem to support methods in classes
and `check_struct_has_member()` only seems to support data members).
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Fixes 2887.
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* SatClauseHashFunction
Added to the same file as SatLiteralHashFunction.
* clang-format
Thanks Andres!
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PR #2786 changed `CryptoMinisatSolver::addClause()` to register clauses
with the bit-vector proof if proofs are turned on. The new code
requested the `ProofManager` even when proofs were turned off, which
made the `eager-inc-cryptominisat.smt2` regression and our nightlies
fail. This commit guards the access to the `ProofManager`, restoring the
semantics of the original code when proofs are turned off.
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* [DRAT] ClausalBitvectorProof
Created a class, `ClausalBitvectorProof`, which represents a bitvector
proof of UNSAT using an underlying clausal technique (DRAT, LRAT, etc)
It fits into the `BitvectorProof` class hierarchy like this:
```
BitvectorProof
/ \
/ \
ClausalBitvectorProof ResolutionBitvectorProof
```
This change is a painful one because all of the following BV subsystems
referenced ResolutionBitvectorProof (subsequently RBVP) or
BitvectorProof (subsequently BVP):
* CnfStream
* SatSolver (specifically the BvSatSolver)
* CnfProof
* TheoryProof
* TheoryBV
* Both bitblasters
And in particular, ResolutionBitvectorProof, the CnfStream, and the
SatSolvers were tightly coupled.
This means that references to and interactions with (R)BVP were
pervasive.
Nevertheless, an SMT developer must persist.
The change summary:
* Create a subclass of BVP, called ClausalBitvectorProof, which has
most methods stubbed out.
* Make a some modifications to BVP and ResolutionBitvectorProof as the
natural division of labor between the different classes becomes
clear.
* Go through all the components in the first list and try to figure
out which kind of BVP they should **actually** be interacting with,
and how. Make tweaks accordingly.
* Add a hook from CryptoMinisat which pipes the produced DRAT proof
into the new ClausalBitvectorProof.
* Add a debug statement to ClausalBitvectorProof which parses and
prints that DRAT proof, for testing purposes.
Test:
* `make check` to verify that we didn't break any old stuff, including
lazy BB, and eager BB when using bvminisat.
* `cvc4 --dump-proofs --bv-sat-solver=cryptominisat --bitblast=eager
-d bv::clausal test/regress/regress0/bv/ackermann2.smt2`, and see that
1. It crashed with "Unimplemented"
2. Right before that it prints out the (textual) DRAT proof.
* Remove 2 unneeded methods
* Missed a rename
* Typos
Thanks Andres!
Co-Authored-By: alex-ozdemir <aozdemir@hmc.edu>
* Address Andres comments
* Reorder members of TBitblaster
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* Split BitvectorProof into a sub/superclass
The superclass contains general printing knowledge.
The subclass contains CNF or Resolution-specific knowledge.
* Renames & code moves
* Nits cleaned in prep for PR
* Moved CNF-proof from ResolutionBitVectorProof to BitVectorProof
Since DRAT BV proofs will also contain a CNF-proof, the CNF proof should
be stored in `BitVectorProof`.
* Unique pointers, comments, and code movement.
Adjusted the distribution of code between BVP and RBVP.
Notably, put the CNF proof in BVP because it isn't
resolution-specific.
Added comments to the headers of both files -- mostly BVP.
Changed two owned pointers into unique_ptr.
BVP's pointer to a CNF proof
RBVP's pointer to a resolution proof
BVP: `BitVectorProof`
RBVP: `ResolutionBitVectorProof`
* clang-format
* Undo manual copyright modification
* s/superclass/base class/
Co-Authored-By: alex-ozdemir <aozdemir@hmc.edu>
* make LFSCBitVectorProof::printOwnedSort public
* Andres's Comments
Mostly cleaning up (or trying to clean up) includes.
* Cleaned up one header cycle
However, this only allowed me to move the forward-decl, not eliminate
it, because there were actually two underlying include cycles that the
forward-decl solved.
* Added single _s to header gaurds
* Fix Class name in debug output
Credits to Andres
Co-Authored-By: alex-ozdemir <aozdemir@hmc.edu>
* Reordered methods in BitVectorProof per original ordering
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The sources of all previous libraries are now added to libcvc4 and built as
libcvc4. This removes circular dependencies between libcvc4 and libexpr.
Further, we now only have one parser library and don't build additional
libraries for each language.
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TODO: cvc4autoconfig.h
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C++11 supports explicitly deleting functions that should not be used
(explictly or implictly), e.g. copy or assignment constructors. We were
previously using the CVC4_UNDEFINED macro that used a compiler-specific
attribute. The C++11 feature should be more portable.
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Eager incremental solving is achieved via solving under assumptions. As soon as incremental and eager bit-blasting is enabled, assertions are passed to the SAT solver as assumptions rather than assertions. This requires the eager SAT solver to support incremental solving, which is currently only supported by CryptoMiniSat.
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Fixes issue #2137. CnfProof has a stack of assertions that are being
converted to clauses. Previously, it could happen that while an
assertion was being added, TheoryProxy::explainPropagation() would be
called from Solver::reason() and push an assertion to the stack that was
then not removed. This lead to a clause id of the assertion being
associated with the explanation instead, which in turn could lead to a
wrong unsat core. This commit identifies two cases where
TheoryProxy::explainPropagation() is called without cleaning up the
assertion stack afterwards. It also adds an assertion that the assertion
stack must be empty when we are getting the unsat core.
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In MiniSat's analyze(), we were taking a reference of a clause that
could be invalidated by a call to resolveOutUnit(). resolveOutUnit() can
lead to allocation of clauses which in turn can lead to clauses being
reallocated, making the reference stale. The commit encloses the
reference in a code block that makes the lifetime of the reference more
obvious and removes uses of the potentially stale reference.
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This commit implements a workaround for computing unsat cores while
doing incremental solving to address #1349. Currently, our resolution
proofs do not handle clauses with a lower-than-assertion-level correctly
because the resolution proofs for them get removed when popping the
context but the SAT solver keeps using them. The workaround changes the
behavior of the SAT solver to add clauses always at the current level if
incremental solving and unsat cores are enabled. This makes sure that
all learned clauses are removed when we pop below the level that they
were learned at. This may degrade performance because the SAT solver has
to relearn clauses.
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Some quick background: CVC4 has two primary contexts: the assertion
context (which corresponds to the push/pops issued by the user) and the
decision/SAT context (which corresponds to the push/pops done by the
user and each decision made by MiniSat.
Before 2cc0e2c6a691fb6d30ed8879832b49bc1f277d77, we had an additonal
push/pop when doing the actual solving. With these removed, it could
happen that we get a wrong result when doing incremental solving:
```
...
; check-sat call returns sat, the decision level in the SAT solver is
; non-zero at this point
(check-sat)
; Solver::addClause_() determines that we cannot add the clause to the
; SAT solver directly because the decision level is non-zero (i.e. the
; clause is treated like a theory lemma), thus it is added to the lemmas
; list.
(assert false)
; The solver stores some information about the current state, including
; the value of the "ok" flag in Solver, which indicates whether the
; current constraints are unsatisfiable. Note that "ok" is true at this
; point.
(push)
; Now, in Solver::updateLemmas(), we add clauses from the lemmas list.
; The problem is that empty clauses (which "false" is after removing "false"
; literals) and unit clauses are not added like normal clauses. Instead,
; the empty clause, essentially just results in the "ok" flag being set to
; false (unit clauses are added to the decision trail).
(check-sat)
; Here, the solver restores the information stored during
; (push), including the "ok" flag, which is now true again.
(pop)
; At this point, the solver has "forgotten" about (assert false) since
; the "ok" flag is back to true and it answers sat.
(check-sat)
```
There are multiple ways to look at the problem and to fix it:
- One could argue that an input assertion should always be added
directly to the clauses in the SAT solver, i.e. the solver should
always be at decision level 0 when we are adding input clauses. The
advantage of this is that it is relatively easy to implement,
corresponds to what the original MiniSat code does (it calls
Solver::cancelUntil(0) after solving), and is no worse than what we had
before commit 2cc0e2c6a691fb6d30ed8879832b49bc1f277d77 (push/pop do a
strict superset of what resetting the decision at the current assertion
level does). The disadvantage is that we might throw away some useful work.
- One could argue that is fine that (assert false) is treated like a
theory lemma. The advantage being that it might result in more efficient
solving and the disadvantage being that it is much trickier to
implement.
Unfortunately, it is not quite clear from the code what the original
intention was but we decided to implement the first solution. This
commit exposes a method in MiniSat to reset the decisions at the current
assertion level. We call this method from SmtEngine after solving.
Resetting the decisions directly after solving while we are still in
MiniSat does not work because it causes issues with datastructures in
the SMT solver that use the decision context (e.g.
TheoryEngine::d_incomplete seems to be reset too early, resulting in us
answering sat instead of unknown).
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In `addClause_()`, we were checking the condition `ca[confl].size() ==
1` regardless if proofs were enabled or not, even though both branches
of the if statement only do something when proofs are enabled. This lead
to issue #1978 occurring even when not generating proofs. Note: This
commit is *not* a fix for #1978 but it makes sure that the issue does
not occur when not generating proofs/unsat cores.
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If analyzeFinal() in BVMiniSat was called with a literal that also
occurred in the trail, it could happen that the set of assumptions that
led to the assignment of `p` contained `p` twice.
BitVectorProof::endBVConflict would then register that conflict with the
duplicate literal but at the same time compute a conflict expression
with the duplicate removed. LFSCSatProof::printAssumptionsResolution
would then output two resolutions for the same literal, which made the
simplify_clause side condition fail because it couldn't find the literal
in the clause anymore after the first removal.
The fix simply avoid adding `p` to the set of assumptions if it is found
in the trail. In this situation, `p` is guaranteed to be in the set of
assumptions already because it has been added at the beginning of
analyzeFinal(). This issue originally came up in PR #1384. With this fix
the regression tests pass in #1384.
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While reviewing #1695, I realized that bvminisat is leaking memory for
each call to setNotify(). This commit uses std::unique_ptr to fix the
issue. It also adds std::unique_ptr to manage d_minisat.
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Cryptominisat has name conflicts with the other Minisat implementations since
the Minisat implementations export var_Undef, l_True, ... as macro whereas
Cryptominisat uses static const. In order to avoid these conflicts we
forward declare CMSat::SATSolver and include the cryptominisat header only
in cryptominisat.cpp.
Further, the helper functions are moved into an anonymous namespace in the .cpp file and functions that were not used are removed.
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* Fixes --hide-zero-stats (and really skips the 0 values)
* Removes the additional newline after each statistic
* Introduces theory::getStatsPrefix(TheoryId) to generate consistent
prefixes for statistics based on the theory id
(e.g., THEORY_BV -> "theory::bv").
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Adds missing override keywords.
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Clang formatted sat_solver_factor.cpp
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Removing more miscellaneous throw specifiers. Also fixing the spelling of amount in several places.
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Also, moved implementation of BVMinisatSatSolver::MinisatNotify::notify to .cpp file.
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* Replacing __gnu_cxx::hash_map with std::unordered_map.
* Replacing __gnu_cxx::hash_set with std::unordered_set.
* Replacing __gnu_cxx::hash with std::hash.
* Adding missing includes.
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This commit fixes bug 821. As written in the description of the bug, the issue
is that `id` is not being set on one of the paths in addClause(), specifically
in the case where all but one literal are assigned false and the remaining
literal is assigned true. In that case, we are not actually adding anything and
set the `id` to `ClauseIdUndef`.
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Boolean terms, treats distinguished BOOLEAN_TERM_VARIABLE kind as theory literal. Fixes bugs 597, 604, 651, 652, 691, 694. Add regressions.
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This reverts commit 3395c5c13cd61d98aec0d9806e3b9bc3d707968a, reversing
changes made to 5f415d4585134612bc24e9a823289fee35541a01.
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Conflicts:
src/options/quantifiers_options
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