Code development
************************


Scientific software development is a crucial aspect of computational
(astro-)physics.  With the progess made over the past decades,
numerical methods as well as implementations have evolved and
increased in complexity. The scope of simulation codes has increased
accordingly, such that the question on how to organize development
becomes important for further scientific progress.

This version of Arepo is intended as a basis, providing an efficient
code structure and state of the art numerical techniques for gravity
and hydrodynamics. The code is completely documented and should allow
computational astrophysicists to develop their own specialized modules
on top of it. Practically, this is best done by hosting an own
repository for the development, which is occasonally updated from the
main repository to include latest bugfixes. For this workflow to work
properly, it is helpful to keep the code-base relatively static. For
this reason

**the base version of the code is not meant to be extended in**
**functionality.**

This means that only bugfixes as well as updates in the documentation
and examples will be included in revisions of this public release.

Issue reporting
===============

A code of the scope of Arepo will inevitably have a number of issues
and so far undiscovered bugs.  Detection of all issues is very
complicated and time-consuming work. This means in practice that we
rely on users to actually report all bugs and issues they come across,
helping us to improve the quality of the code. We therefore encourage
users to report all issues they have, including things that remain
unclear after reading the documentation. This way we hope to
constantly improve the qualtiy of the code in all its aspects.
 
To organize this, we set up a code support forum
(www.arepo-code.org/forums/forum/arepo-forum) which is publicly
visible. To create posts on this forum, a registration with
admin-approval is required. We encourage users to sign up under
www.arepo-code.org/register and make use of the forum whenever they
have problems.

Issues reported in the forum will then be confirmed by one of the
authors and added to the repository issue tracker, which serves as a
to-do list for bug fixes and improvements to the code. Therefore, if a
problem occurs, the first thing to check is whether there already
exists an open issue, i.e. whether this is a known and confirmed
problem.

**Please whenever possible use the support forum instead of contacting**
**the authors by email.**

**We encourage experienced users to provide help and answer some of**
**the open questions on this forum.**


Code extensions 
===============

Extensions should be hosted in separate repositories or branches of
the main repository.  We highly welcome such extensions and encourage
developers to make them publicly available (under GNU GPL v3). While
this can be done independently of the authors, we would encourage
developers to inform the authors once there is a publicly available
module they are willing to share, in order to have a list of available
extensions on the code homepage.

Some guidelines for code extensions and new modules:

  * Strive for modularity
 
  * Minimize the number of changes in existing source code files to a
    few function calls and structured variables within existing
    elements.
	
  * The source code of a new modue should largely be in separate
    (i.e. new) files.
  
  * Document the module
 
  * All parameter and config-options should be clearly explained in
    this documentation.  Feel free to add an addional page to this
    documentation explaining how your module works.
	
  * Document what each function does in the source code.
	
  * The Template-Config.sh file should have a short explanation for
    each added flag.
  
  * Verification and examples
 
  * If possible, create one or more addional examples illustrating and
    testing the module.