.. _site-configuration:

Site configuration
===================================

.. _temp-space:

Temporary space
----------------------------

.. warning:: Temporary space configuration will eventually be moved to
   configuration files, but currently these settings are in
   ``lib/spack/spack/__init__.py``

By default, Spack will try to do all of its building in temporary
space.  There are two main reasons for this.  First, Spack is designed
to run out of a user's home directory, and on may systems the home
directory is network mounted and potentially not a very fast
filesystem.  We create build stages in a temporary directory to avoid
this.  Second, many systems impose quotas on home directories, and
``/tmp`` or similar directories often have more available space.  This
helps conserve space for installations in users' home directories.

You can customize temporary directories by editing
``lib/spack/spack/__init__.py``.  Specifically, find this part of the file:

.. code-block:: python

   # Whether to build in tmp space or directly in the stage_path.
   # If this is true, then spack will make stage directories in
   # a tmp filesystem, and it will symlink them into stage_path.
   use_tmp_stage = True

   # Locations to use for staging and building, in order of preference
   # Use a %u to add a username to the stage paths here, in case this
   # is a shared filesystem.  Spack will use the first of these paths
   # that it can create.
   tmp_dirs = ['/nfs/tmp2/%u/spack-stage',
               '/var/tmp/%u/spack-stage',
               '/tmp/%u/spack-stage']

The ``use_tmp_stage`` variable controls whether Spack builds
**directly** inside the ``var/spack/`` directory.  Normally, Spack
will try to find a temporary directory for a build, then it *symlinks*
that temporary directory into ``var/spack/`` so that you can keep
track of what temporary directories Spack is using.

The ``tmp_dirs`` variable is a list of paths Spack should search when
trying to find a temporary directory.  They can optionally contain a
``%u``, which will substitute the current user's name into the path.
The list is searched in order, and Spack will create a temporary stage
in the first directory it finds to which it has write access.  Add
more elements to the list to indicate where your own site's temporary
directory is.


External Packages
~~~~~~~~~~~~~~~~~~~~~
Spack can be configured to use externally-installed
packages rather than building its own packages. This may be desirable
if machines ship with system packages, such as a customized MPI
that should be used instead of Spack building its own MPI.

External packages are configured through the ``packages.yaml`` file found
in a Spack installation's ``etc/spack/`` or a user's ``~/.spack/``
directory. Here's an example of an external configuration:

.. code-block:: yaml

   packages:
      openmpi:
         paths:
            openmpi@1.4.3%gcc@4.4.7=chaos_5_x86_64_ib: /opt/openmpi-1.4.3
            openmpi@1.4.3%gcc@4.4.7=chaos_5_x86_64_ib+debug: /opt/openmpi-1.4.3-debug
            openmpi@1.6.5%intel@10.1=chaos_5_x86_64_ib: /opt/openmpi-1.6.5-intel

This example lists three installations of OpenMPI, one built with gcc,
one built with gcc and debug information, and another built with Intel.
If Spack is asked to build a package that uses one of these MPIs as a
dependency, it will use the the pre-installed OpenMPI in
the given directory.  

Each ``packages.yaml`` begins with a ``packages:`` token, followed
by a list of package names.  To specify externals, add a ``paths``
token under the package name, which lists externals in a
``spec : /path`` format.  Each spec should be as
well-defined as reasonably possible.  If a
package lacks a spec component, such as missing a compiler or
package version, then Spack will guess the missing component based
on its most-favored packages, and it may guess incorrectly.

Each package version and compilers listed in an external should
have entries in Spack's packages and compiler configuration, even
though the package and compiler may not every be built.

The packages configuration can tell Spack to use an external location
for certain package versions, but it does not restrict Spack to using
external packages.  In the above example, if an OpenMPI 1.8.4 became
available Spack may choose to start building and linking with that version
rather than continue using the pre-installed OpenMPI versions.

To prevent this, the ``packages.yaml`` configuration also allows packages
to be flagged as non-buildable.  The previous example could be modified to
be:

.. code-block:: yaml

  packages:
    openmpi:
      paths:
        openmpi@1.4.3%gcc@4.4.7=chaos_5_x86_64_ib: /opt/openmpi-1.4.3
        openmpi@1.4.3%gcc@4.4.7=chaos_5_x86_64_ib+debug: /opt/openmpi-1.4.3-debug
        openmpi@1.6.5%intel@10.1=chaos_5_x86_64_ib: /opt/openmpi-1.6.5-intel                
      buildable: False

The addition of the ``buildable`` flag tells Spack that it should never build
its own version of OpenMPI, and it will instead always rely on a pre-built
OpenMPI.  Similar to ``paths``, ``buildable`` is specified as a property under
a package name.

The ``buildable`` does not need to be paired with external packages.  
It could also be used alone to forbid packages that may be 
buggy or otherwise undesirable.


Profiling
~~~~~~~~~~~~~~~~~~~~~

Spack has some limited built-in support for profiling, and can report
statistics using standard Python timing tools.  To use this feature,
supply ``-p`` to Spack on the command line, before any subcommands.

.. _spack-p:

``spack -p``
^^^^^^^^^^^^^^^^^^

``spack -p`` output looks like this:

.. code-block:: sh

   $ spack -p graph dyninst
   o  dyninst
   |\
   | |\
   | o |  libdwarf
   |/ /
   o |  libelf
    /
   o  boost

         307670 function calls (305943 primitive calls) in 0.127 seconds

   Ordered by: internal time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      853    0.021    0.000    0.066    0.000 inspect.py:472(getmodule)
    51197    0.011    0.000    0.018    0.000 inspect.py:51(ismodule)
    73961    0.010    0.000    0.010    0.000 {isinstance}
     1762    0.006    0.000    0.053    0.000 inspect.py:440(getsourcefile)
    32075    0.006    0.000    0.006    0.000 {hasattr}
     1760    0.004    0.000    0.004    0.000 {posix.stat}
     2240    0.004    0.000    0.004    0.000 {posix.lstat}
     2602    0.004    0.000    0.011    0.000 inspect.py:398(getfile)
      771    0.004    0.000    0.077    0.000 inspect.py:518(findsource)
     2656    0.004    0.000    0.004    0.000 {method 'match' of '_sre.SRE_Pattern' objects}
    30772    0.003    0.000    0.003    0.000 {method 'get' of 'dict' objects}
    ...

The bottom of the output shows the top most time consuming functions,
slowest on top.  The profiling support is from Python's built-in tool,
`cProfile
<https://docs.python.org/2/library/profile.html#module-cProfile>`_.
