Difference between revisions of "User Manual"

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This manual includes lots of information about how to use CVC4.
+
This manual includes information on installing and using CVC4. It is a work in progress.  
  
It is a work in-progress.
+
=Getting CVC4=
  
= What is CVC4? =
+
Both pre-compiled binaries and the source code for CVC4 are available for download from [http://cvc4.cs.stanford.edu/downloads/builds/ http://cvc4.cs.stanford.edu/downloads/builds/].
  
CVC4 is the last of a long line of SMT solvers that started with SVC and includes CVC, CVC-Lite and CVC3.
+
==Getting CVC4 binaries==
Technically, it is an automated validity checker for a many-sorted (i.e., typed) first-order logic with built-in theories.
+
The most recent binaries can be downloaded from our Nightly Builds pages:
The current built-in theories are the theories of:
+
* [http://cvc4.cs.stanford.edu/downloads/builds/x86_64-linux-opt/ Optimized] binaries (statically linked)
 +
* [http://cvc4.cs.stanford.edu/downloads/builds/x86_64-linux-dbg/ Debug] binaries (statically linked)
 +
* [http://cvc4.cs.stanford.edu/downloads/builds/debian/ Debian] packages
  
* equality over free (aka uninterpreted) function and predicate symbols,
+
'''[Not ported to Stanford yet]''' To install CVC4 on an Ubuntu Machine follow the instructions below. First add the CVC4 repository to /etc/apt/source.list by inserting the following two lines at the end of the file:
* real and integer linear arithmetic (with some support for non-linear arithmetic),
+
  # CVC4 repository
* bit vectors,
+
  deb http://cvc4.cs.nyu.edu/debian/ unstable/
* arrays,
+
  deb-src http://cvc4.cs.nyu.edu/debian/ unstable/
* tuples,
+
* records,
+
* user-defined inductive data types.
+
  
CVC4 checks whether a given formula <math>\phi</math> is valid in the built-in theories under a given set <math>\Gamma</math> of assumptions, a ''context''.  
+
To run CVC4 as a binary you only need the first line but to use the library API you will also need the source package.  
More precisely, it checks whether
+
Make sure to update the respository list by running:
  
<center>
+
  sudo apt-get update
<math>\Gamma\models_T \phi</math>
+
</center>
+
  
that is, whether <math>\phi</math> is a logical consequence in <math>T</math> of the set of formulas <math>\Gamma</math>, where <math>T</math> is the union of CVC4's built-in theories.
+
Now you can simply install CVC4 as you would any other piece of sofware using the command:
 +
  sudo apt-get install cvc4
  
Roughly speaking, when <math>\phi</math> is a universal formula and <math>\Gamma</math> is a set of existential formulas (i.e., when <math>\phi</math> and <math>\Gamma</math> contain at most universal, respectively existential, quantifiers), CVC4 is a decision procedure:
+
If you want to use CVC4 as a library also install the following packages: libcvc4-dev, and libcvc4-parser-dev.
it is guaranteed (modulo bugs and memory limits) to return a correct "valid" or "invalid" answer eventually.
+
In all other cases, CVC4 is deductively sound but incomplete:  
+
it will never say that an invalid formula is valid,
+
but it may either never return or give up and return "unknown" for some formulas.
+
  
Currently, when CVC4 returns "valid" for a query formula <math>\phi</math> under a context <math>\Gamma</math>
+
==Building CVC4 from source==
it provides no evidence to back its claim.
+
[http://cvc4.cs.stanford.edu/downloads/builds/src/ Sources are available] from the same site as the binaries. The source-code is also available in the [https://github.com/CVC4/CVC4 CVC4 source repository].  
Future versions will also return a ''proof certificate'',
+
a formal proof that <math>\Gamma'\models_T \phi</math> for some subset <math>\Gamma'</math> of <math>\Gamma</math>.
+
  
When CVC4 returns "invalid" it can return
+
To build CVC4 from source the following steps are required. After downloading the source files first install antlr by running the following script in the CVC4 contrib directory:
both a ''counter-example'' to <math>\phi</math>'s validity under the context <math>\Gamma</math> and a ''counter-model''.
+
Both a counter-example and a counter-model are a set <math>\Delta</math> of additional formulas consistent with <math>\Gamma</math> in <math>T</math>, but entailing the negation of <math>\phi</math>.
+
Formally:
+
 
+
<center>
+
<math>\Gamma \cup \Delta \not\models_T \mathit{false}</math>
+
and
+
<math>\Gamma \cup \Delta \models_T \lnot \phi</math>.
+
</center>
+
 
+
The difference is that a counter-model is given as a set of equations providing a concrete assignment of values for the free symbols in <math>\Gamma</math> and <math>\phi</math>
+
(see the section on [[#CVC4's native input language|CVC4's native input language]] for more details).
+
 
+
=Obtaining and compiling CVC4=
+
 
+
CVC4 is distributed in the following ways:
+
* [[#Obtaining_binary_packages|Binary packages]]
+
* [[#Obtaining_source_packages|Source packages]]
+
* [[#Source_repository|Source repository checkout]]
+
 
+
==Obtaining binary packages==
+
 
+
[http://cvc4.cs.nyu.edu/builds/ Binary packages are available] for CVC4.
+
Nightly builds:
+
* [http://cvc4.cs.nyu.edu/builds/debian/unstable Debian] packages
+
* [http://cvc4.cs.nyu.edu/builds/x86_64-linux-opt/ Optimized] binaries (statically linked)
+
* [http://cvc4.cs.nyu.edu/builds/x86_64-linux-dbg/ Debug] binaries (statically linked)
+
 
+
==Obtaining source packages==
+
 
+
[http://cvc4.cs.nyu.edu/builds/src/ Sources are available] from the same site as the binaries.
+
 
+
==Source repository==
+
The [http://cvc4.cs.nyu.edu/builds/src/ CVC4 source repository] is currently hosted by [http://cims.nyu.edu/ CIMS] and requires a CIMS account. Please contact a member of the development team for access. Please see the additional instructions for [[Building CVC4 from source #Building_CVC4 from_a_repository_checkout | here]].
+
 
+
==Building from source==
+
 
+
To compile from a source package:
+
# Install antlr
+
# Configure cvc4
+
# Compile cvc4
+
# Install cvc4 [optional]
+
 
     cd contrib
 
     cd contrib
 
     ./get-antlr-3.4
 
     ./get-antlr-3.4
 +
 +
The next step is to configure CVC4:
 
     cd ..
 
     cd ..
 
     ./configure --with-antlr-dir=`pwd`/antlr-3.4 ANTLR=`pwd`/antlr-3.4/bin/antlr3
 
     ./configure --with-antlr-dir=`pwd`/antlr-3.4 ANTLR=`pwd`/antlr-3.4/bin/antlr3
 +
 +
And then finally compile it:
 
     make
 
     make
 
     make check  [recommended]
 
     make check  [recommended]
 
     make install [optional]
 
     make install [optional]
  
(To build from a repository checkout, see [[Building CVC4 from source #Building_CVC4_from_a_repository_checkout|here]].)
+
For a comprehensive list of dependencies and more detailed build instructions see [[Building CVC4 from source]].
 
+
For more detailed build instructions and dependencies see [[Building CVC4 from source]]
+
  
 
=Using the CVC4 binary=
 
=Using the CVC4 binary=
Line 207: Line 159:
 
==Exit status==
 
==Exit status==
  
The exit status of CVC4 depends on the ''last'' QUERY or CHECK-SATIf you wish to call CVC4 from a program (e.g., a shell script) and care only about the satisfiability or validity of a single formula, you can pass the ''-q'' option (as described [[#Verbosity|above, under verbosity]]) and check the exit code.  With ''-q'', CVC4 should not produce any output unless it encounters a fatal error.
+
Successful exit is marked by the exit code 0Most "normal errors" return a 1 as the exit code, but out of memory conditions, terminating signals, and other conditions can produce different (nonzero) exit codes.  In interactive mode, parse errors are ignored and the next line read; so in interactive mode, you may see an exit code of 0 even in the presence of such an error.
  
QUERY asks a validity question, and CHECK-SAT a satisfiability question, and these are dual problems; hence the terminology is different, but really "sat" and "invalid" are the same internally, as are "unsat" and "valid":
+
''Note on previous versions:'' Up to version 1.2 of CVC4, exit status depended on the result ("sat" results caused an exit code of 10, "unsat" of 20). This behavior was deemed nonstandard and is no longer the case; successful exits are always 0 in version 1.3 and later.
 
+
<table border="1">
+
<tr><th>Solver's last result</th><th>Exit code</th><th>Notes</th></tr>
+
<tr><td>'''sat''' or '''invalid'''</td><td>10</td></tr>
+
<tr><td>'''unsat''' or '''valid'''</td><td>20</td></tr>
+
<tr><td>'''unknown'''</td><td>0</td><td>could be for any reason: time limit exceeded, no memory, incompleteness..</td></tr>
+
<tr><td>''no result''</td><td>0</td><td>no query or check-sat command issued</td></tr>
+
<tr><td>parse errors</td><td>0 (in interactive mode)<br/>1 (otherwise)</td><td>see below</td></tr>
+
<tr><td>other errors</td><td>1 (usually)</td><td>see below</td></tr>
+
</table>
+
 
+
Most "normal errors" return a 1 as the exit code, but out of memory conditions, and others, can produce different exit codes.  In interactive mode, parse errors are ignored and the next line read; so in interactive mode, you may see an exit code of 0 even in the presence of such an error.
+
 
+
In SMT-LIB mode, an SMT-LIB command script that sets its status via "set-info :status" also affects the exit code.  So, for instance, the following SMT-LIB script returns an exit code of 10 even though it contains no "check-sat" command:
+
 
+
(set-logic QF_UF)
+
  (set-info :status sat)
+
(exit)
+
 
+
Without the "set-info," it would have returned an exit code of 0.
+
  
 
=CVC4's input languages=
 
=CVC4's input languages=
Line 235: Line 167:
 
When not used in interactive mode, CVC4 can read its input from an external file. It accepts the following input languages:  
 
When not used in interactive mode, CVC4 can read its input from an external file. It accepts the following input languages:  
  
* [[CVC4's native language ]]
+
* [[CVC4's native language | CVC4's native language]]
* SMT-LIB 2.0  
+
* SMT-LIB 2.0 (see [http://www.grammatech.com/resources/smt/SMTLIBTutorial.pdf David Cok's SMT-LIB tutorial])
 
* SMT-LIB 1.0
 
* SMT-LIB 1.0
  
CVC4 tries to automatically recognize the input language based on the file's extension: cvc for CVC4's native language, smt2 for SMT-LIB 2.0 and smt for SMT-LIB 1.0. If the file extension does not match one of the previously mentioned ones you can specify the input language via the command line flag --lang. To see all language options type:
+
CVC4 tries to automatically recognize the input language based on the file's extension: .cvc for CVC4's native language, .smt2 for SMT-LIB 2.0 and .smt for SMT-LIB 1.0. If the file extension does not match one of the previously mentioned ones you can specify the input language via the command line flag --lang. To see all language options type:
  $cvc4 --lang help
+
  $ cvc4 --lang help
 
+
=CVC4's support for the SMT-LIB language=
+
 
+
==SMT-LIB compliance==
+
  
 
Every effort has been made to make CVC4 compliant with the SMT-LIB 2.0
 
Every effort has been made to make CVC4 compliant with the SMT-LIB 2.0
Line 253: Line 181:
 
somewhat lenient; some non-conforming input may still be parsed and
 
somewhat lenient; some non-conforming input may still be parsed and
 
processed.
 
processed.
 +
 +
=Supported Theories=
 +
The following theories are currently fully supported
 +
* Booleans
 +
* Uninterpreted functions
 +
* Arrays [with extensionality]
 +
* Inductive datatypes
 +
* Tuples and record types
 +
* Fixed width bitvectors
 +
* Linear mixed real integer arithmetic
 +
** Integer division and modulus by integer constants is supported by the "--rewrite-divk" flag
 +
* [[sets|Finite sets]]
 +
CVC4 supports first-order quantification and theory combinations of the above theories.
 +
 +
 +
The following theories are currently partially supported and are undergoing development:
 +
* Strings
 +
 +
Theories with '''highly limited''' support:
 +
* CVC4's non-linear real and non-linear integer arithmetic support is currently unlikely to satisfy a user's needs.  The current support is for parsing, rewrites, and a very limited class of proofs of unsatisifiability. The class of proofs is what is provable by linear arithmetic where each monomial (e.g. "xxy") is treated as a unique variable.
  
 
=The CVC4 library interface (API)=
 
=The CVC4 library interface (API)=
 +
 +
There are a number of examples of using CVC4 as a library distributed with the source code of the project. There are given in the "/examples" directory.
 +
 
==Using CVC4 in a C++ project==
 
==Using CVC4 in a C++ project==
 +
 +
A basic C++ example for using cvc4 is given in the file [https://github.com/CVC4/CVC4/blob/master/examples/simple_vc_cxx.cpp /examples/simple_vc_cxx.cpp].
 +
The file goes through the examples for the basic interaction with CVC4:
 +
# Constructing an ExprManager em
 +
# Constructing an SmtEngine w.r.t. em.
 +
# Getting a copy of the Type for mathematical integers from em, em.integerType().
 +
# Constructing new Expressions
 +
## Integer variables x and y: Expr x = em.mkVar("x", integer);
 +
## The rational constant 0: em.mkConst(Rational(0));
 +
## Constructing new expressions existing expressions: em.mkExpr(kind::GT, x, zero);
 +
# Querying the SmtEngine whether or not a formula is valid.
 +
 +
 +
 +
More information on the interfaces for Expr, Type, ExprManager and SmtEngine can be found in their respective header files.
 +
 +
To compile simple_vc_cxx.cpp, there are different build instructions for whether or not you are compiling against a version of CVC4 in a local build directory or one installed via "make install" into a directory $PREFIX.
 +
 +
* Local Build Directory: If you have build cvc4 via the "make" command before, you can compile simple_vc_cxx.cpp via "make examples". The executable will then be "./builds/examples/simple_vc_cxx".
 +
 +
    $ make examples
 +
    [...]
 +
    $ ./builds/examples/simple_vc_cxx
 +
    Checking validity of formula ((x > 0) AND (y > 0)) => (((2 * x) + y) >= 3) with CVC4.
 +
    CVC4 should report VALID.
 +
    Result from CVC4 is: valid
 +
* Installed Copy: If you have installed CVC4 via "make install" into the directory $PREFIX (which you can configure via "./configure --prefix=$PREFIX" you will need to modify lines 21-22.
 +
    //#include <cvc4/cvc4.h> // use this after CVC4 is properly installed
 +
    #include "smt/smt_engine.h"
 +
:First, uncomment line 21 and comment out line 22. You may now
 +
You can now compile and run by executing
 +
    g++ -I$PREFIX/include -L$PREFIX/lib -lcvc4 examples/simple_vc_cxx.cpp -o simple_vc_cxx
 +
    ./simple_vc_cxx
 +
:You may need to add $PREFIX/lib is LD_LIBRARY_PATH or the equivalent.
 +
 
==Using CVC4 from Java==
 
==Using CVC4 from Java==
 
==The compatibility interface==
 
==The compatibility interface==
Line 318: Line 304:
 
===If you were using CVC3 from Java===
 
===If you were using CVC3 from Java===
  
=Useful command-line options=
+
=Advanced features=
  
==Statistics==
+
This section describes some features of CVC4 of interest to developers and advanced users.
  
Statistics can be dumped on exit (both normal and abnormal exits) with
+
==Resource limits==
the --statistics command line option.
+
 
+
==Time and resource limits==
+
  
 
CVC4 can be made to self-timeout after a given number of milliseconds.
 
CVC4 can be made to self-timeout after a given number of milliseconds.
Line 350: Line 333:
 
heap.
 
heap.
  
=Dumping API calls or preprocessed output=
+
==Dumping API calls or preprocessed output==
  
=Changing the output language=
+
[to do]
  
=Proof support=
+
==Changing the output language==
 +
 
 +
[to do]
 +
 
 +
==Proof support==
  
 
CVC4 1.0 has limited support for proofs, and they are disabled by default.
 
CVC4 1.0 has limited support for proofs, and they are disabled by default.
Line 362: Line 349:
 
release).
 
release).
  
=Portfolio solving=
+
==Parallel solving==
 +
 
 +
'''[Builds not ported to Stanford yet]''' The most recent binaries with support for parallel solving can be downloaded from our Nightly Builds pages:
 +
* [http://cvc4.cs.nyu.edu/cvc4-builds/portfolio-x86_64-linux-opt/ Optimized] binaries (statically linked)
 +
* [http://cvc4.cs.nyu.edu/cvc4-builds/portfolio-x86_64-linux-dbg/ Debug] binaries (statically linked)
  
 
If enabled at configure-time (./configure --with-portfolio), a second
 
If enabled at configure-time (./configure --with-portfolio), a second
Line 374: Line 365:
 
literals that are "local" to one thread.)
 
literals that are "local" to one thread.)
  
Currently, the portfolio **does not work** with quantifiers or with
+
Currently, the portfolio **does not work** with the theory of inductive
the theory of inductive datatypes. These limitations will be addressed
+
datatypes. This limitation will be addressed in a future release.
in a future release.
+
 
 +
See more details and examples in the [[Tutorials#Parallel_Solving|tutorial]].
  
=Emacs support=
+
==Emacs support==
  
 
For a suggestion of editing CVC4 source code with emacs, see the file
 
For a suggestion of editing CVC4 source code with emacs, see the file
 
contrib/editing-with-emacs.  For a CVC language mode (the native input
 
contrib/editing-with-emacs.  For a CVC language mode (the native input
 
language for CVC4), see contrib/cvc-mode.el.
 
language for CVC4), see contrib/cvc-mode.el.

Revision as of 11:26, 8 February 2017

This manual includes information on installing and using CVC4. It is a work in progress.

Getting CVC4

Both pre-compiled binaries and the source code for CVC4 are available for download from http://cvc4.cs.stanford.edu/downloads/builds/.

Getting CVC4 binaries

The most recent binaries can be downloaded from our Nightly Builds pages:

[Not ported to Stanford yet] To install CVC4 on an Ubuntu Machine follow the instructions below. First add the CVC4 repository to /etc/apt/source.list by inserting the following two lines at the end of the file:

 # CVC4 repository
 deb http://cvc4.cs.nyu.edu/debian/ unstable/
 deb-src http://cvc4.cs.nyu.edu/debian/ unstable/

To run CVC4 as a binary you only need the first line but to use the library API you will also need the source package. Make sure to update the respository list by running:

 sudo apt-get update

Now you can simply install CVC4 as you would any other piece of sofware using the command:

 sudo apt-get install cvc4

If you want to use CVC4 as a library also install the following packages: libcvc4-dev, and libcvc4-parser-dev.

Building CVC4 from source

Sources are available from the same site as the binaries. The source-code is also available in the CVC4 source repository.

To build CVC4 from source the following steps are required. After downloading the source files first install antlr by running the following script in the CVC4 contrib directory:

   cd contrib
   ./get-antlr-3.4

The next step is to configure CVC4:

   cd ..
   ./configure --with-antlr-dir=`pwd`/antlr-3.4 ANTLR=`pwd`/antlr-3.4/bin/antlr3

And then finally compile it:

   make
   make check   [recommended]
   make install [optional]

For a comprehensive list of dependencies and more detailed build instructions see Building CVC4 from source.

Using the CVC4 binary

Once installed, the CVC4 driver binary ("cvc4") can be executed to directly enter into interactive mode:

$ cvc4
cvc4 1.0 assertions:off
CVC4>

You can then enter commands into CVC4 interactively:

CVC4> OPTION "incremental";
CVC4> OPTION "produce-models";
CVC4> TRANSFORM 25*25;
625
CVC4> x, y : INT;
CVC4> QUERY x = y;
invalid
CVC4> COUNTERMODEL;
x : INT = -1;
y : INT = 0;
CVC4> ASSERT x >= 0;
CVC4> QUERY x = y;
invalid
CVC4> COUNTERMODEL;
x : INT = 0;
y : INT = 1;
CVC4>

The above example shows two useful options, incremental and produce-models.

  • The incremental option allows you to issue multiple QUERY (or CHECKSAT) commands, and allows the use of the PUSH and POP commands. Without this option, CVC4 optimizes itself for a single QUERY or CHECKSAT command (though you may issue any number of ASSERT commands). The incremental option may also be given by passing the -i command line option to CVC4.
  • The produce-models option allows you to query the model (here, with the COUNTERMODEL command) after an "invalid" QUERY (or "satisfiable" CHECK-SAT). Without it, CVC4 doesn't do the bookkeeping necessary to support model generation. The produce-models option may also be given by passing the -m command line option to CVC4.

So, if you invoke CVC4 with -im, you don't need to pass those options at all:

$ cvc4 -im
cvc4 1.0 assertions:off
CVC4> x, y : INT;
CVC4> QUERY x = y;
invalid
CVC4> COUNTERMODEL;
x : INT = -1;
y : INT = 0;
CVC4> ASSERT x >= 0;
CVC4> QUERY x = y;
invalid
CVC4> COUNTERMODEL;
x : INT = 0;
y : INT = 1;
CVC4>

By default, CVC4 operates in CVC-language mode. If you enter something that looks like SMT-LIB, it will suggest that you use the "--lang smt" command-line option for SMT-LIB mode:

CVC4> (declare-fun x () Int)
Parse Error: <shell>:1.7: In CVC4 presentation language mode, but SMT-LIB format detected.  Use --lang smt for SMT-LIB support.
CVC4>

Verbosity

CVC4 has various levels of verbosity. By default, CVC4 is pretty quiet, only reporting serious warnings and notices. If you're curious about what it's doing, you can pass CVC4 the -v option:

$ cvc4 -v file.smt2
Invoking: (set-logic AUFLIRA)
Invoking: (set-info :smt-lib-version 2.000000)
Invoking: (set-info :category "crafted")
Invoking: (set-info :status unsat)
Invoking: (declare-fun x () Real)
etc...

For even more verbosity, you can pass CVC4 an additional -v:

$ cvc4 -vv file.smt2
Invoking: (set-logic AUFLIRA)
Invoking: (set-info :smt-lib-version 2.000000)
Invoking: (set-info :category "crafted")
Invoking: (set-info :status unsat)
Invoking: (declare-fun x () Real)
etc...
expanding definitions...
constraining subtypes...
applying substitutions...
simplifying assertions...
doing static learning...
etc...

Internally, verbosity is just an integer value. It starts at 0, and with every -v on the command line it is incremented; with every -q, decremented. It can also be set directly. From CVC language:

CVC4> OPTION "verbosity" 2;

Or from SMT-LIB language:

CVC4> (set-option :verbosity 2)

Getting statistics

Statistics can be dumped on exit (both normal and abnormal exits) with the --statistics command line option.

$ cvc4 --statistics foo.smt2
sat
sat::decisions, 0
sat::propagations, 3
sat::starts, 1
theory::uf::TheoryUF::functionTermsCount, 2
theory::uf::TheoryUF::mergesCount, 2
theory::uf::TheoryUF::termsCount, 6
theory<THEORY_UF>::propagations, 1 
driver::filename, foo.smt2
driver::sat/unsat, sat
driver::totalTime, 0.02015373
[many others]

Many statistics name-value pairs follow, one comma-separated pair per line.

Exit status

Successful exit is marked by the exit code 0. Most "normal errors" return a 1 as the exit code, but out of memory conditions, terminating signals, and other conditions can produce different (nonzero) exit codes. In interactive mode, parse errors are ignored and the next line read; so in interactive mode, you may see an exit code of 0 even in the presence of such an error.

Note on previous versions: Up to version 1.2 of CVC4, exit status depended on the result ("sat" results caused an exit code of 10, "unsat" of 20). This behavior was deemed nonstandard and is no longer the case; successful exits are always 0 in version 1.3 and later.

CVC4's input languages

When not used in interactive mode, CVC4 can read its input from an external file. It accepts the following input languages:

CVC4 tries to automatically recognize the input language based on the file's extension: .cvc for CVC4's native language, .smt2 for SMT-LIB 2.0 and .smt for SMT-LIB 1.0. If the file extension does not match one of the previously mentioned ones you can specify the input language via the command line flag --lang. To see all language options type:

$ cvc4 --lang help

Every effort has been made to make CVC4 compliant with the SMT-LIB 2.0 standard (http://smtlib.org/). However, when parsing SMT-LIB input, certain default settings don't match what is stated in the official standard. To make CVC4 adhere more strictly to the standard, use the "--smtlib" command-line option. Even with this setting, CVC4 is somewhat lenient; some non-conforming input may still be parsed and processed.

Supported Theories

The following theories are currently fully supported

  • Booleans
  • Uninterpreted functions
  • Arrays [with extensionality]
  • Inductive datatypes
  • Tuples and record types
  • Fixed width bitvectors
  • Linear mixed real integer arithmetic
    • Integer division and modulus by integer constants is supported by the "--rewrite-divk" flag
  • Finite sets

CVC4 supports first-order quantification and theory combinations of the above theories.


The following theories are currently partially supported and are undergoing development:

  • Strings

Theories with highly limited support:

  • CVC4's non-linear real and non-linear integer arithmetic support is currently unlikely to satisfy a user's needs. The current support is for parsing, rewrites, and a very limited class of proofs of unsatisifiability. The class of proofs is what is provable by linear arithmetic where each monomial (e.g. "xxy") is treated as a unique variable.

The CVC4 library interface (API)

There are a number of examples of using CVC4 as a library distributed with the source code of the project. There are given in the "/examples" directory.

Using CVC4 in a C++ project

A basic C++ example for using cvc4 is given in the file /examples/simple_vc_cxx.cpp. The file goes through the examples for the basic interaction with CVC4:

  1. Constructing an ExprManager em
  2. Constructing an SmtEngine w.r.t. em.
  3. Getting a copy of the Type for mathematical integers from em, em.integerType().
  4. Constructing new Expressions
    1. Integer variables x and y: Expr x = em.mkVar("x", integer);
    2. The rational constant 0: em.mkConst(Rational(0));
    3. Constructing new expressions existing expressions: em.mkExpr(kind::GT, x, zero);
  5. Querying the SmtEngine whether or not a formula is valid.


More information on the interfaces for Expr, Type, ExprManager and SmtEngine can be found in their respective header files.

To compile simple_vc_cxx.cpp, there are different build instructions for whether or not you are compiling against a version of CVC4 in a local build directory or one installed via "make install" into a directory $PREFIX.

  • Local Build Directory: If you have build cvc4 via the "make" command before, you can compile simple_vc_cxx.cpp via "make examples". The executable will then be "./builds/examples/simple_vc_cxx".
   $ make examples
   [...]
   $ ./builds/examples/simple_vc_cxx 
   Checking validity of formula ((x > 0) AND (y > 0)) => (((2 * x) + y) >= 3) with CVC4.
   CVC4 should report VALID.
   Result from CVC4 is: valid
  • Installed Copy: If you have installed CVC4 via "make install" into the directory $PREFIX (which you can configure via "./configure --prefix=$PREFIX" you will need to modify lines 21-22.
   //#include <cvc4/cvc4.h> // use this after CVC4 is properly installed
   #include "smt/smt_engine.h"
First, uncomment line 21 and comment out line 22. You may now

You can now compile and run by executing

   g++ -I$PREFIX/include -L$PREFIX/lib -lcvc4 examples/simple_vc_cxx.cpp -o simple_vc_cxx
   ./simple_vc_cxx
You may need to add $PREFIX/lib is LD_LIBRARY_PATH or the equivalent.

Using CVC4 from Java

The compatibility interface

Upgrading from CVC3 to CVC4

Features not supported by CVC4 (yet)

Type Correctness Conditions (TCCs)

Type Correctness Conditions (TCCs), and the checking of such, are not supported by CVC4 1.0. Thus, a function defined only on integers can be applied to REAL (as INT is a subtype of REAL), and CVC4 will not complain, but may produce strange results. For example:

 f : INT -> INT;
 ASSERT f(1/3) = 0;
 ASSERT f(2/3) = 1;
 CHECKSAT;
 % sat
 COUNTEREXAMPLE;
 % f : (INT) -> INT = LAMBDA(x1:INT) : 0;

CVC3 can be used to produce TCCs for this input (with the +dump-tcc option). The TCC can be checked by CVC3 or another solver. (CVC3 can also check TCCs while solving with +tcc.)

If you were using the text interfaces of CVC3

The native language of all solvers in the CVC family, referred to as the "presentation language," has undergone some revisions for CVC4. The most notable is that CVC4 does _not_ add counterexample assertions to the current assertion set after a SAT/INVALID result. For example:

 x, y : INT;
 ASSERT x = 1 OR x = 2;
 ASSERT y = 1 OR y = 2;
 ASSERT x /= y;
 CHECKSAT;
 % sat
 QUERY x = 1;
 % invalid
 QUERY x = 2;
 % invalid

Here, CVC4 responds "invalid" to the second and third queries, because each has a counterexample (x=2 is a counterexample to the first, and x=1 is a counterexample to the second). However, CVC3 will respond with "valid" to one of these two, as the first query (the CHECKSAT) had the side-effect of locking CVC3 into one of the two cases; the later queries are effectively querying the counterexample that was found by the first. CVC4 removes this side-effect of the CHECKSAT and QUERY commands.

CVC4 supports rational literals (of type REAL) in decimal; CVC3 did not support decimals.

CVC4 does not have support for the IS_INTEGER predicate.

If you were using the library ("in-memory") interface of CVC3

If you were using CVC3 from C

If you were using CVC3 from Java

Advanced features

This section describes some features of CVC4 of interest to developers and advanced users.

Resource limits

CVC4 can be made to self-timeout after a given number of milliseconds. Use the --tlimit command line option to limit the entire run of CVC4, or use --tlimit-per to limit each individual query separately. Preprocessing time is not counted by the time limit, so for some large inputs which require aggressive preprocessing, you may notice that --tlimit does not work very well. If you suspect this might be the case, you can use "-vv" (double verbosity) to see what CVC4 is doing.

Time-limited runs are not deterministic; two consecutive runs with the same time limit might produce different results (i.e., one may time out and responds with "unknown", while the other completes and provides an answer). To ensure that results are reproducible, use --rlimit or --rlimit-per. These options take a "resource count" (presently, based on the number of SAT conflicts) that limits the search time. A word of caution, though: there is no guarantee that runs of different versions of CVC4 or of different builds of CVC4 (e.g., two CVC4 binaries with different features enabled, or for different architectures) will interpret the resource count in the same manner.

CVC4 does not presently have a way to limit its memory use; you may opt to run it from a shell after using "ulimit" to limit the size of the heap.

Dumping API calls or preprocessed output

[to do]

Changing the output language

[to do]

Proof support

CVC4 1.0 has limited support for proofs, and they are disabled by default. (Run the configure script with --enable-proof to enable proofs). Proofs are exported in LFSC format and are limited to the propositional backbone of the discovered proof (theory lemmas are stated without proof in this release).

Parallel solving

[Builds not ported to Stanford yet] The most recent binaries with support for parallel solving can be downloaded from our Nightly Builds pages:

  • Optimized binaries (statically linked)
  • Debug binaries (statically linked)

If enabled at configure-time (./configure --with-portfolio), a second CVC4 binary will be produced ("pcvc4"). This binary has support for running multiple instances of CVC4 in different threads. Use --threads=N to specify the number of threads, and use --thread0="options for thread 0" --thread1="options for thread 1", etc., to specify a configuration for the threads. Lemmas are *not* shared between the threads by default; to adjust this, use the --filter-lemma-length=N option to share lemmas of N literals (or smaller). (Some lemmas are ineligible for sharing because they include literals that are "local" to one thread.)

Currently, the portfolio **does not work** with the theory of inductive datatypes. This limitation will be addressed in a future release.

See more details and examples in the tutorial.

Emacs support

For a suggestion of editing CVC4 source code with emacs, see the file contrib/editing-with-emacs. For a CVC language mode (the native input language for CVC4), see contrib/cvc-mode.el.