.. _dev_start_guide:

=====================
Developer Start Guide
=====================

Resources
=========

See :ref:`theano_community` for a list of Theano resources. The
following groups/mailing-lists are especially useful to Theano
contributors: `theano-dev`_, `theano-buildbot`_, and `theano-github`_.

.. _theano-dev: https://groups.google.com/group/theano-dev
.. _theano-github: https://groups.google.com/group/theano-github
.. _theano-buildbot: https://groups.google.com/group/theano-buildbot


To get up to speed, you'll need to

- Learn some non-basic Python to understand what's going on in some of the
  trickier files (like tensor.py).
- Go through the `NumPy documentation`_.
- Learn to write reStructuredText_ for epydoc_ and Sphinx_.
- Learn about how unittest_ and nose_ work

.. _Sphinx: http://sphinx.pocoo.org/
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
.. _epydoc: http://epydoc.sourceforge.net/
.. _NumPy documentation: http://docs.scipy.org/numpy/
.. _unittest: http://docs.python.org/library/unittest.html
.. _nose: http://somethingaboutorange.com/mrl/projects/nose/


Installation and configuration
==============================

To obtain developer access: register with `GitHub
<http://www.github.com/>`_ and create a fork of `Theano
<http://www.github.com/Theano/Theano>`_.

This will create your own Theano project on GitHub, referred later
as "YourProfile/Theano", or "origin", from which you will be able to
contribute to the original Theano/Theano, also called "central".


Create a local copy
-------------------

Clone your fork locally with

.. code-block:: bash

    git clone git@github.com:your_github_login/Theano.git

From your local repository, your own fork on GitHub will be called "origin".

Then, add a reference to the original ("central") Theano repository with

.. code-block:: bash

    git remote add central git://github.com/Theano/Theano.git

You can choose another name than "central" to reference Theano/Theano
(for instance, NumPy uses "upstream"), but this documentation will stick
to "central."

You can then test your installation of Theano by following the steps of
:ref:`testing_installation`.


Using your local copy
---------------------

To update your library to the latest revision, you should have a local branch
that tracks central/master. You can add one (named "trunk" here) with:

.. code-block:: bash

    git fetch central
    git branch trunk central/master

Once you have such a branch, in order to update it, do:

.. code-block:: bash

    git checkout trunk
    git pull

Keep in mind that this branch should be "read-only": if you want to
patch Theano, you should work in another branch, like described in the
:ref:`dev_workflow` section below.


Configure Git
-------------

On your local machine, you need to configure git with basic informations:

.. code-block:: bash

   git config --global user.email you@yourdomain.example.com
   git config --global user.name "Your Name Comes Here"


You can also instruct git to use color in diff. For this, you need to
add those lines in the file ~/.gitconfig

.. code-block:: cfg

    [color]
       branch = auto
       diff = auto
       interactive = auto
       status = auto


.. _dev_workflow:

Development Workflow
====================

Start a new local branch
------------------------

When working on a new feature in your own fork, start from an up-to-date copy
of the `master` branch (the principal one) of the central repository
(Theano/Theano on GitHub):

.. code-block:: bash

    git fetch central
    git checkout -b my_shiny_feature central/master

.. note::

    This last line is a shortcut for:

    .. code-block:: bash

        git branch my_shiny_feature central/master
        git checkout my_shiny_feature


Submit your changes to the central repository
---------------------------------------------

Once your code is ready for others to review, you need to push your
branch to your github fork first:

.. code-block:: bash

    git push -u origin my_shiny_feature

Then, go to your fork's github page on the github website, select your
feature branch and hit the "Pull Request" button in the top right
corner.  This will signal the maintainers that you wish to submit your
changes for inclusion in central/master.
If you don't get any feedback, bug us on the theano-dev mailing list.


Address reviewer comments
-------------------------

Your pull request will be reviewed by members of the core development
team. If your branch is not directly accepted, the reviewers will use
GitHub's system to add "notes", either general (on the entire commit),
or "line notes", relative to a particular line of code.
In order to have the pull request accepted, you may have to answer
the reviewer's questions, you can do that on GitHub.

You may also have to edit your code to address their concerns. Some
of the usual requests include fixing typos in comments, adding or
correcting comments, adding unit tests in the test suite.  In order to
do that, you should continue your edits in the same branch you used (in
this example, "my_shiny_feature").  For instance, if you changed your
working branch, you should first:

.. code-block:: bash

    git checkout my_shiny_feature

Then, edit your code, and test it appropriately (see
:ref:`quality_contributions` below), and push it again to your GitHub
fork, like the first time (except the ``-u`` option is only needed the
first time):

.. code-block:: bash

    git push origin my_shiny_feature

The pull request to the central repository will then be automatically
updated by GitHub. However, the reviewers will not be automatically
notified of your revision, so it is advised to reply to the comments on
GitHub, to let them know that you have submitted a fix.


.. _quality_contributions:

Tips for Quality Contributions
==============================

Coding Style Auto Check
-----------------------

In Theano, we use the same coding style as the `Pylearn
<http://deeplearning.net/software/pylearn/v2_planning/API_coding_style.html>`_
project, except that we don't use the numpy docstring standard.
The principal thing to know is that we follow the
`pep8 <http://www.python.org/dev/peps/pep-0008/>`_ coding style.

We use git hooks provided in the project `pygithooks
<https://github.com/lumberlabs/pygithooks>`_ to validate that commits
respect pep8. This happens when each user commits, not when we
push/merge to the Theano repository. Github doesn't allow us to have
code executed when we push to the repository. So we ask all
contributors to use those hooks.

For historic reason, we currently don't have all files respecting pep8.
We decided to fix everything incrementally. So not all files respect it
now. So we strongly suggest that you use the "increment" pygithooks
config option to have a good workflow. See the pygithooks main page
for how to set it up for Theano and how to enable this option.


Unit tests
----------

Before submitting a pull request, you should run the unit test suite,
and make sure that your changes did not create any new Error or Failure.
You can consult `theano-buildbot`_ for the result of a recent run
of the test suite with various options.

To run the test suite with the default options, you can follow the
instructions of :ref:`testing_installation`.

Each night we execute all the unit tests automatically, with different
sets of options.  The result is sent by email to the `theano-buildbot`_
mailing list.

For more detail, see :ref:`metadocumentation_nightly_build`.

To run all the tests with the same configuration as the buildbot, run this script:

.. code-block:: bash

   theano/misc/do_nightly_build

This function accepts arguments that it forward to nosetests. You can
run only some tests or enable pdb by giving the equivalent nosetests
parameters.



More Advanced Git Usage
=======================

You can find information and tips in the `numpy development
<http://docs.scipy.org/doc/numpy/dev/gitwash/development_workflow.html>`_
page. Here are a few.


Cleaning up branches
--------------------

When your pull request has been merged, you can delete the branch from
your GitHub fork's list of branches. This is useful to avoid having too
many branches staying there. Deleting this remote branch is achieved
with:

.. code-block:: bash

   git push origin :my_shiny_feature

This lines pushes to the "origin" repository (your fork of Theano on
GitHub), into the branch "my_shiny_feature", an empty content (that's
why there is nothing before the colon), effectively removing it.

The branch will still be present in your local clone of the repository.
If you want to delete it from there, too, you can run:

.. code-block:: bash

   git branch -d my_shiny_feature


Amending a submitted pull request
---------------------------------

If you want to fix a commit already submitted within a pull request
(e.g. to fix a small typo), before the pull request is accepted, you can
do it like this to keep history clean:

.. code-block:: bash

   git checkout my_shiny_feature
   git commit --amend
   git push origin my_shiny_feature:my_shiny_feature

Do not abuse that command, and please use it only when there are only
small issues to be taken care of. Otherwise, it becomes difficult to
match the comments made by reviewers with the new modifications.
In the general case, you should stick with the approach described above.


Cleaning up history
-------------------

Sometimes you may have commits in your feature branch that
are not needed in the final pull request. There is a `page
<http://sandofsky.com/blog/git-workflow.html>`_ that talks about
this. In summary:

* Commits to the trunk should be a lot cleaner than commits to your
  feature branch; not just for ease of reviewing but also
  because intermediate commits can break blame (the bisecting tool).
* `git merge --squash` will put all of the commits from your feature branch into one commit.
* There are other tools that are useful if your branch is too big for one squash.


Add another distant repository
------------------------------

To collaborate with another user on some feature he is developing, and
that is not ready for inclusion in central, the easiest way is to use a
branch of their Theano fork (usually on GitHub).

Just like we added Theano/Theano as a remote repository, named
"central", you can add (on your local machine) a reference to their fork
as a new remote repository. REPO_NAME is the name you choose to name
this fork, and GIT_REPO_PATH is the URL of the fork in question.

.. code-block:: bash

    git remote add REPO_NAME GIT_REPO_PATH

Then, you can create a new local branch (LOCAL_BRANCH_NAME) based on
a specific branch (REMOTE_BRANCH_NAME) from the remote repository
(REPO_NAME):

.. code-block:: bash

   git checkout -b LOCAL_BRANCH_NAME REPO_NAME/REMOTE_BRANCH_NAME
