Directory structure

The SKIRT source code is contained in an online repository and can be obtained as described in the Installation Guide. The files are organized in a nested directory hierarchy; your local copy may look as follows:

~/SKIRT
    debug
    git
        Docs
        MakeUp
        SKIRT
        SMILE
    release
        ...
        MakeUp
        SKIRT
        ...
    resources
        ...
        SKIRT9_Resources_Core
    run

The git directory contains an identical copy of the online SKIRT repository; it is usually placed inside a local directory called SKIRT in your home directory. The debug and release directories contain the result of building the SKIRT code, including the executables. Always use the release build for "production" simulations; the code in the debug build is not optimized and runs several times slower. The resources directory contains resource files required by SKIRT and downloaded from the SKIRT web site. The run directory may contain input/output files involved in actually running SKIRT. The information in these last four directories is not part of the source code repository, which is why these directories are not inside the git directory.

Immediately inside the git directory reside the main project file CMakeLists.txt and some shell scripts used for building SKIRT or its documentation. For more information, see the Installation Guide and Generating the SKIRT project documentation.

The highest-level git subdirectories (MakeUp, SKIRT, SMILE) each represent a subproject of the SKIRT project. In their turn, they have nested subdirectories organizing the source code and related support files into modules.

Subprojects and modules

The above diagram lists the various subprojects and modules in the SKIRT code. Boxes with a gray background depict a subproject; the other boxes depict a module. A colored border indicates that the module contains supporting data files rather than source code. Most module boxes represent a static library that can be used by other modules; those with a symbol in the upper right corner represent an executable program.

The symbols in the upper left corner of each module box indicate internal and external dependencies. Refer to the diagram legend for details. Note that there are no two-way or circular dependencies between modules. When adjusting or extending the code, it is important not to inadvertently create new inter-module dependencies. In any case, circular dependencies between modules are not allowed.

These are the subprojects of the SKIRT code:

SMILE – contains the code for generic, fundamental facilities, including those for handling XML-based parameter files; see The SMILE metadata subproject.
SKIRT – contains the code for the SKIRT command line program, performing radiative transfer simulations; see SKIRT Q&A and command line options.
MakeUp – contains the code for the MakeUp tool that provides a graphical user interface for configuring SKIRT; see MakeUp, the graphical interface for SKIRT parameter files.
Docs – contains data files and a helper tool that support writing and building the reference documentation for the SKIRT code; see Generating the SKIRT project documentation.

Below is a brief description of the modules in each of these subproject, listed in order of appearance in the above diagram.

SMILE subproject (also see The SMILE metadata subproject):

build – This small library allows retrieving versioning information about the current build. It cooperates with the build system to provide information such as the time when the current executable was built.
fundamentals – This library offers generic functionality that is used by other modules throughout the project, including platform-independent system interaction, basic string handling, and low-level XML processing.
schema – This library contains the meat of the SMILE functionality, including facilities for processing SMILE schemas, representing SMILE datasets in memory, and performing introspection on C++ classes in SMILE client code.
serialize – This library uses the capabilities of the schema module to serialize and deserialize SMILE data sets, and to resurrect a client's C++ object hierarchy from a SMILE dataset.
wizard – This library implements the graphical wizard that allows creating or editing a SMILE dataset, given the corresponding SMILE schema file.
smiletool – This command-line tool can work with SMILE datasets corresponding to a given SMILE schema file. The tool can conduct a text-based question and answer session to create a dataset, produce a LaTeX description for an existing dataset, and more.
shapes – This command-line program serves as an example of the typical SMILE library use case (similar to but a lot less complex than SKIRT).

SKIRT subproject (also see SKIRT Q&A and command line options):

resources – This module includes information on which resource data files are required by the various classes in the SKIRT/core module.
fitsio – This library provides input/output capabilities for FITS files. It contains a subset of the cfitsio source files available from NASA's HEASARC software site. For more information see The CFITSIO third-party library.
voro – This library provides support for building Voronoi tessellations. The source code is adapted from the Voro++ library written by Chris H. Rycroft (LBL / UC Berkeley). For more information see The Voro++ third-party library.
mpi – This library encapsulates any and all invocations of the Message Passing Interface (MPI) optionally linked in as an external library. Concentrating all MPI calls in a single module allows the code in other modules to be compiled without the MPI extra's.
utils – This library provides some basic SKIRT-specific functionality that does not depend on the SimulationItem class.
core – This library provides the core SKIRT functionality for setting up and performing a simulation. It includes all SimulationItem subclasses and the corresponding registry. Also see The ins and outs of simulation items.
main – This is the SKIRT console application. It handles the command line arguments and links in everything else from other libraries.

MakeUp subproject (also see MakeUp, the graphical interface for SKIRT parameter files):

main – This desktop program displays a graphical user interface for editing parameter files. The code in this module essentially invokes the functionality provided by the wizard module in the SMILE project.

Docs subproject (also see Generating the SKIRT project documentation):

templates – This module includes some developer support data files, such as the license template to be included in every source file.
doxygen – This module includes some data files to support the generation of reference documentation from the project source code through the Doxygen utility.
doxstyle – This console application can be invoked from the Qt Creator code editor to help streamline Doxygen documentation blocks, as explained in Formatting the source code. The code in this module depends only on the fundamentals module in the SMILE subproject; it is included here so that it would be easily available to any SKIRT developer.