Bindings to CryptoMiniSat 5.0.1 (a SAT solver)

## Project description

===========================================

pycryptosat: bindings to the CryptoMiniSat SAT solver

===========================================

This directory provides Python bindings to CryptoMiniSat on the C++ level,

i.e. when importing pycryptosat, the CryptoMiniSat solver becomes part of the

Python process itself.

Compiling

-----

The pycryptosat python package compiles while compiling CryptoMiniSat. It

cannotbe compiled on its own, it must be compiled at the same time as

CryptoMiniSat. You will need the python development libraries in order to

compile:

```

apt-get install python-dev

```

After this, cmake then indicate that pycryptosat will be compiled:

```

cd cryptominisat

mkdir build

cd build

cmake ..

[...]

-- Found PythonInterp: /usr/bin/python2.7 (found suitable version "2.7.9", minimum required is "2.7")

-- Found PythonLibs: /usr/lib/x86_64-linux-gnu/libpython2.7.so (found suitable version "2.7.9", minimum required is "2.7")

-- PYTHON_EXECUTABLE:FILEPATH=/usr/bin/python2.7

-- PYTHON_LIBRARY:FILEPATH=/usr/lib/x86_64-linux-gnu/libpython2.7.so

-- PYTHON_INCLUDE_DIR:FILEPATH=/usr/include/python2.7

-- PYTHONLIBS_VERSION_STRING=2.7.9

-- OK, found python interpreter, libs and header files

-- Building python interface

[...]

```

It will then generate the pycryptosat library and install it when calling

`make install`.

Usage

-----

The ``pycryptosat`` module has one object, ``Solver`` that has two functions

``solve`` and ``add_clause``.

The funcion ``add_clause()`` takes an iterable list of literals such as

``[1, 2]`` which represents the truth ``1 or 2 = True``. For example,

``add_clause([1])`` sets variable ``1`` to ``True``.

The function ``solve()`` solves the system of equations that have been added

with ``add_clause()``:

>>> from pycryptosat import Solver

>>> s = Solver()

>>> s.add_clause([1, 2])

>>> sat, solution = s.solve()

>>> print sat

True

>>> print solution

(None, True, True)

The return value is a tuple. First part of the tuple indicates whether the

problem is satisfiable. In this case, it's ``True``, i.e. satisfiable. The second

part is a tuple contains the solution, preceded by None, so you can index into

it with the variable number. E.g. ``solution[1]`` returns the value for

variabe ``1``.

The ``solve()`` method optionally takes an argument ``assumptions`` that

allows the user to set values to specific variables in the solver in a temporary

fashion. This means that in case the problem is satisfiable but e.g it's

unsatisfiable if variable 2 is FALSE, then ``solve([-2])`` will return

UNSAT. However, a subsequent call to ``solve()`` will still return a solution.

If instead of an assumption ``add_clause()`` would have been used, subsequent

``solve()`` calls would have returned unsatisfiable.

``Solver`` takes the following keyword arguments:

* ``confl_limit``: the propagation limit (integer)

* ``verbose``: the verbosity level (integer)

The ``confl_limit`` argument sets a kind of time-out limit to the solver. If

the solver runs out of time, it returns with ``(None, None)``.

Example

-------

Let us consider the following clauses, represented using

the DIMACS `cnf <http://en.wikipedia.org/wiki/Conjunctive_normal_form>`_

format::

p cnf 5 3

1 -5 4 0

-1 5 3 4 0

-3 -4 0

Here, we have 5 variables and 3 clauses, the first clause being

(x\ :sub:`1` or not x\ :sub:`5` or x\ :sub:`4`).

Note that the variable x\ :sub:`2` is not used in any of the clauses,

which means that for each solution with x\ :sub:`2` = True, we must

also have a solution with x\ :sub:`2` = False. In Python, each clause is

most conveniently represented as a list of integers. Naturally, it makes

sense to represent each solution also as a list of integers, where the sign

corresponds to the Boolean value (+ for True and - for False) and the

absolute value corresponds to i\ :sup:`th` variable::

>>> import pycryptosat

>>> solver = pycryptosat.Solver()

>>> solver.add_clause([1, -5, 4])

>>> solver.add_clause([-1, 5, 3, 4])

>>> solver.add_clause([-3, -4])

>>> solver.solve()

(True, (None, True, False, False, True, True))

This solution translates to: x\ :sub:`1` = x\ :sub:`4` = x\ :sub:`5` = True,

x\ :sub:`2` = x\ :sub:`3` = False

pycryptosat: bindings to the CryptoMiniSat SAT solver

===========================================

This directory provides Python bindings to CryptoMiniSat on the C++ level,

i.e. when importing pycryptosat, the CryptoMiniSat solver becomes part of the

Python process itself.

Compiling

-----

The pycryptosat python package compiles while compiling CryptoMiniSat. It

cannotbe compiled on its own, it must be compiled at the same time as

CryptoMiniSat. You will need the python development libraries in order to

compile:

```

apt-get install python-dev

```

After this, cmake then indicate that pycryptosat will be compiled:

```

cd cryptominisat

mkdir build

cd build

cmake ..

[...]

-- Found PythonInterp: /usr/bin/python2.7 (found suitable version "2.7.9", minimum required is "2.7")

-- Found PythonLibs: /usr/lib/x86_64-linux-gnu/libpython2.7.so (found suitable version "2.7.9", minimum required is "2.7")

-- PYTHON_EXECUTABLE:FILEPATH=/usr/bin/python2.7

-- PYTHON_LIBRARY:FILEPATH=/usr/lib/x86_64-linux-gnu/libpython2.7.so

-- PYTHON_INCLUDE_DIR:FILEPATH=/usr/include/python2.7

-- PYTHONLIBS_VERSION_STRING=2.7.9

-- OK, found python interpreter, libs and header files

-- Building python interface

[...]

```

It will then generate the pycryptosat library and install it when calling

`make install`.

Usage

-----

The ``pycryptosat`` module has one object, ``Solver`` that has two functions

``solve`` and ``add_clause``.

The funcion ``add_clause()`` takes an iterable list of literals such as

``[1, 2]`` which represents the truth ``1 or 2 = True``. For example,

``add_clause([1])`` sets variable ``1`` to ``True``.

The function ``solve()`` solves the system of equations that have been added

with ``add_clause()``:

>>> from pycryptosat import Solver

>>> s = Solver()

>>> s.add_clause([1, 2])

>>> sat, solution = s.solve()

>>> print sat

True

>>> print solution

(None, True, True)

The return value is a tuple. First part of the tuple indicates whether the

problem is satisfiable. In this case, it's ``True``, i.e. satisfiable. The second

part is a tuple contains the solution, preceded by None, so you can index into

it with the variable number. E.g. ``solution[1]`` returns the value for

variabe ``1``.

The ``solve()`` method optionally takes an argument ``assumptions`` that

allows the user to set values to specific variables in the solver in a temporary

fashion. This means that in case the problem is satisfiable but e.g it's

unsatisfiable if variable 2 is FALSE, then ``solve([-2])`` will return

UNSAT. However, a subsequent call to ``solve()`` will still return a solution.

If instead of an assumption ``add_clause()`` would have been used, subsequent

``solve()`` calls would have returned unsatisfiable.

``Solver`` takes the following keyword arguments:

* ``confl_limit``: the propagation limit (integer)

* ``verbose``: the verbosity level (integer)

The ``confl_limit`` argument sets a kind of time-out limit to the solver. If

the solver runs out of time, it returns with ``(None, None)``.

Example

-------

Let us consider the following clauses, represented using

the DIMACS `cnf <http://en.wikipedia.org/wiki/Conjunctive_normal_form>`_

format::

p cnf 5 3

1 -5 4 0

-1 5 3 4 0

-3 -4 0

Here, we have 5 variables and 3 clauses, the first clause being

(x\ :sub:`1` or not x\ :sub:`5` or x\ :sub:`4`).

Note that the variable x\ :sub:`2` is not used in any of the clauses,

which means that for each solution with x\ :sub:`2` = True, we must

also have a solution with x\ :sub:`2` = False. In Python, each clause is

most conveniently represented as a list of integers. Naturally, it makes

sense to represent each solution also as a list of integers, where the sign

corresponds to the Boolean value (+ for True and - for False) and the

absolute value corresponds to i\ :sup:`th` variable::

>>> import pycryptosat

>>> solver = pycryptosat.Solver()

>>> solver.add_clause([1, -5, 4])

>>> solver.add_clause([-1, 5, 3, 4])

>>> solver.add_clause([-3, -4])

>>> solver.solve()

(True, (None, True, False, False, True, True))

This solution translates to: x\ :sub:`1` = x\ :sub:`4` = x\ :sub:`5` = True,

x\ :sub:`2` = x\ :sub:`3` = False

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