Building and Installing
-----------------------

PyTrilinos is a Trilinos package, and so is built by building Trilinos
in the normal way and enabling the PyTrilinos package.  Trilinos uses
the CMake build system, which requires a build directory separate from
the source directory.  Trilinos builds tend to be complex enough that
it is recommended that you write a short script to invoke ``cmake`` to
configure the build.  See the Trilinos documentation for more details.

PyTrilinos is not enabled by default.  To enable PyTrilinos, use the
``cmake`` option::

    -D Trilinos_ENABLE_PyTrilinos:BOOL=ON

PyTrilinos requires that all of Trilinos be built as shared
libraries.  This is not the default, nor does enabling PyTrilinos set
this flag.  You must therefore explicitly turn on shared libraries::

    -D BUILD_SHARED_LIBS:BOOL=ON

If you enable PyTrilinos but forget to turn on shared libraries,
``cmake`` will exit and give you a gentle reminder to set this option.

Trilinos Packages
^^^^^^^^^^^^^^^^^

PyTrilinos will build python interfaces only for those Trilinos
packages that are enabled.  Some of the default packages have python
wrappers, some do not.  Some Trilinos packages with python wrappers
are not in the default set.  So not specifically enabling any other
Trilinos packages (i.e., using the default set of packages) will build
an incomplete PyTrilinos.

The simplest way to enable every Trilinos package that has a python
interface is to use::

    -D Trilinos_ENABLE_ALL_OPTIONAL_PACKAGES:BOOL=ON

All packages with python wrappers are seen as optional packages to
PyTrilinos, so they all get enabled.  But this directive is recursive,
so those packages that are optional to PyTrilinos also have optional
packages, and they get enabled as well.  This approach will build
several more packages than you need.

For complete control, you can use the option::

    -D Trilinos_ENABLE_ALL_PACKAGES:BOOL=OFF

and then individually enable every package you want using::

    -D Trilinos_ENABLE_<PACKAGE>:BOOL=ON

where ``<PACKAGE>`` is the name of a Trilinos package.  The Trilinos
packages with python interfaces are Teuchos, Epetra, Triutils,
EpetraExt, AztecOO, Galeri, Amesos, Ifpack, Komplex, Anasazi, ML and
NOX.

Python and SWIG
^^^^^^^^^^^^^^^

You may specify the python interpreter (and thus the version of the
Python/C API) with the ``cmake`` option::

    -D PYTHON_EXECUTABLE:FILEPATH=...

If you do not specify this option, ``cmake`` actually looks for an
executable named ``python2.7`` (and then ``python2.6``, etc., down to
``python1.5``, and then finally for ``python``).

The SWIG executable my be similarly specified with::

    -D SWIG_EXECUTABLE:FILEPATH=...

If this option is not used, ``cmake`` will find the first occurence of
``swig`` in your environment's path.

Installation Path
^^^^^^^^^^^^^^^^^

Because PyTrilinos is imported into a running ``python`` interpreter,
and that interpreter will have specific places it looks for python
modules, it is possible to set the PyTrilinos installation path
separately from the Trilinos installation path.  Use::

  -D PyTrilinos_INSTALL_PREFIX:PATH=...

If this option is not specified, then the PyTrilinos installation path
prefix is defined by the Trillinos installation path prefix::

  -D CMAKE_INSTALL_PREFIX:PATH=...

If neither of these options is specified, then the PyTrilinos
installation path is set to be the location where the ``python``
executable expects to find python modules.  Since specifying the
PyTrilinos installation location is more complex than for the rest of
Trilinos, the PyTrilinos installation path is written to the screen
near the end of the configuration process.

Build Time
^^^^^^^^^^

Trilinos can take a long time to configure and build, depending on the
number of packages that are enabled.  A significant portion of this
time can be taken up by building tests and examples.  You can save a
considerable amount of time by turning these tests and examples off::

    -D Trilinos_ENABLE_TESTS:BOOL=OFF
    -D Trilinos_ENABLE_EXAMPLES:BOOL=OFF

Configuring and Building
^^^^^^^^^^^^^^^^^^^^^^^^

To configure Trilinos, run ``cmake`` with the desired options
specified, followed by the path to the top Trilinos source directory.
This will generate the build system.  On a Unix machine, then run
``make`` to build all of the enabled Trilinos packages.  Then run
``make install`` (or ``sudo make install``, if installing to a path
that requires root privileges) to install the Trilinos libraries,
header files and python modules to their proper place.
