Summer of Code - Getting Started

The following is distilled from the Projects page for the benefit of potential Google and ESA Summer of Code (SoC) students. Although students are welcome to attempt any of the projects in that page or any of their own choosing, here we offer some suggestions on what good student projects might be.

Steps Toward a Successful Application

• Help Us Get To Know You

  If you aren't communicating with us before the application is due, your application will not be accepted.

  • Join the maintainers mailing list or read the archives and see what topics we discuss and how the developers interact with each other.
  • Hang out in our IRC channel. Ask questions, answer questions from users, show us that you are motivated, and well-prepared. There will be more applicants than we can effectively mentor, so do ask for feedback on your public application to increase the strength of your proposal!

• Do not wait for us to tell you what to do

  You should be doing something that interests you, and should not need us to tell you what to do. Similarly, you shouldn't ask us what to do either.

  • When you email the list and mentors, do not write it to say on what project you're interested. Be specific about your questions and clear on the email subject. For example, do not write an email with the subject "GSoC student interested in the ND images projects". Such email is likely be ignored. Instead, show you are already working on the topic, and email "Problem implementing morphological operators with bitpacked ND images".
  • It is good to ask advice on how to solve something you can't but you must show some work done. Remember, we are mentors and not your boss. Read How to ask questions the smart way:

    Prepare your question. Think it through. Hasty-sounding questions get hasty answers, or none at all. The more you do to demonstrate that having put thought and effort into solving your problem before seeking help, the more likely you are to actually get help.

  • It can be difficult at the beginning to think on something to do. This is nature of free and open source software development. You will need to break the mental barrier that prevents you from thinking on what can be done. Once you do that, you will have no lack of ideas for what to do next.
  • Use Octave. Eventually you will come accross somethings that does not work the way you like. Fix that. Or you will come accross a missing function. Implement it. It may be a difficult problem (they usually are) but while solving that problem you may find other missing functions (). Implemenent and contribute those to Octave.
  • Take a look at the Short projects for something that may be simple to start with.

• Find Something That Interests You

  It's critical that you find a project that excites you. You'll be spending most of the summer working on it (we expect you to treat the SoC as a full-time job).

  Don't just tell us how interested you are, show us that you're willing and able to contribute to Octave. You can do that by fixing a few bugs or submitting patches well before the deadline, in addition to regularly interacting with Octave maintainers and users on the mailing list and IRC. Our experience shows us that successful SoC students demonstrate their interest early and often.

• Prepare Your Proposal With Us

  By working with us to prepare your proposal, you'll be getting to know us and showing us how you approach problems. The best place for this is your Wiki user page and the IRC channel.

• Complete Your Application

  Fill out our public application template.

  • This is best done by creating an account at this wiki, and copying the template from its page.
  • You really only need to copy and answer the public part there, there is no need to showcase everything else to everybody reading your user page!

  Fill out our private application template.

  • This is best done by copying the template from its page and adding the required information to your application at Google (melange) or at ESA.
    
  • Only the organization admin and the possible mentors will see this data. You can still edit it after submitting until the deadline!

Things You'll be Expected to Know or Quickly Learn On Your Own

Octave is mostly written in C++ and its own scripting language that is mostly compatible with Matlab. There are bits and pieces of Fortran, Perl, C, awk, and Unix shell scripts here and there. In addition to being familiar with C++ and Octave's scripting language, successful applicants will be familiar with or able to quickly learn about Octave's infrastructure. You can't spend the whole summer learning how to build Octave or prepare a changeset and still successfully complete your project.

• The Build System

  The GNU build system is used to build Octave.

  While you generally don't need to understand too much unless you actually want to change how Octave is built, you should be able to understand enough to get a general idea of how to build Octave.

  If you've ever done a configure && make && make install series of commands, you have already used the GNU build system.

  You must demonstrate that you are able to build the development version of Octave from sources before the application deadline. You will be able to find instructions how to it on this wiki, and the manual. Linux is arguably the easiest system to work on.

  • Building_for_Linux_systems
  • Building
  • Octave Manual on Building the Development Sources
  • Octave Manual on Installing Octave

• The Version Control System

  We use Mercurial (abbreviated hg).

  Mercurial is the distributed version control system (DVCS) we use for managing our source code. You should have some basic understanding of how a DVCS works, but hg is pretty easy to pick up, especially if you already know a VCS like git or svn.

• The Procedure for Contributing Changesets

  You will be expected to follow the same procedures as other contributors and core developers.

  You will be helping current and future Octave developers by using our standard style for changes, commit messages, and so on. You should also read the same contribution guidelines we have for everyone.

  This page describes the procedures students are expected to use to publicly display their progress in a public mercurial repo during their work.

• The Maintainers Mailing List

  We primarily use mailing lists for communication among developers.

  The mailing list is used most often for discussions about non-trivial changes to Octave, or for setting the direction of development.

  You should follow basic mailing list etiquette. For us, this mostly means "do not top post".

• The IRC Channel

  We also have the #octave IRC channel in Freenode.

  You should be familiar with the IRC channel. It's very helpful for new contributors (you) to get immediate feedback on ideas and code.

  Unless your primary mentor has a strong preference for some other method of communication, the IRC channel will likely be your primary means of communicating with your mentor and Octave developers.

• The Octave Forge Project

  Octave-Forge is a collection of contributed packages that enhance the capabilities of core Octave. They are somewhat analogous to Matlab's toolboxes.

• Related Skills

  In addition, you probably should know some mathematics, engineering, experimental science, or something of the sort.

  If so, you probably have already been exposed to the kinds of problems that Octave is used for.

Criteria by which applications are judged

These might vary somewhat depending on the mentors and coordinators for a particular Summer of Code, but typically the main factors considered would be:

• Applicant has demonstrated an ability to make substantial modifications to Octave

  The most important thing is that you've contributed some interesting code samples to judge you by. It's OK during the application period to ask for help on how to format these code samples, which normally are Mercurial patches.

• Applicant shows understanding of topic

  Your application should make it clear that you're reasonably well versed in the subject area and won't need all summer just to read up on it.

• Applicant shows understanding of and interest in Octave development

  The best evidence for this is previous contributions and interactions.

• Well thought out, adequately detailed, realistic project plan

  "I'm good at this, so trust me" isn't enough. You should describe which algorithms you'll use and how you'll integrate with existing Octave code. You should also prepare a full timeline and goals for the midterm and final evaluations.

Suggested projects

The following projects are broadly grouped by category and probable skills required to tackle each. Remember to check Projects for more ideas if none of these suit you, and your own ideas are always welcome.

these are suggested projects but you are welcome to propose your own projects provided you find an Octave mentor

Numerical

These projects involve implementing certain mathematical functions, primarily in core Octave.

Make specfuns special again

Traditionally, problem solving environments like Octave provide simple interfaces to numerical linear algebra, special function evaluation, root finding, and other tools. Special functions (such as Bessel functions, exponential integrals, LambertW, etc) are expected by users to "just work". But many of Octave's special functions could be improved to improve their numerical accuracy. Generally a user might expect these to be accurate to full 15 digits. Software testing is important to Octave; this project would improve the tests of many special functions, in particular by comparing the output with slow-but-accurate symbolic computations.

State: some bugs include #48307, #47738, TODO: add others? The unmaintained specfun pkg had some poor implementations (e.g., divergence for large x, see https://github.com/cbm755/octsympy/issues/416.). See also the Symbolic functions in `@double`: these probably should have native double implementations.

• Required skills

Octave m-file programming, some familiarity with Approximation Theory (a branch of mathematics).

• Difficulty

Medium (mathematics needed, but on the other hand, perhaps little or no C++).

• Potential mentors

Colin Macdonald?, others?

How to get started: pick a special function, see if it has tests: contribute a patch that adds more tests comparing its values to symbolic computations.

ode15s : Matlab Compatible DAE solver

The goal is to implement a Matlab compatible adaptive BDF solver for Differential Algebraic Equations (DAEs). The interface would need to be compatible with ode15s while for the backend the SUNDIALS library would be used, which has both a C and a MEX interface. This function should eventually be included in Octave core together with the other ODE solvers that will be released with version 4.2, but could be intially developed as an addition to the odepkg package.

• Required skills

C++; C; familiarity with numerical methods for DAEs; Basic knowledge of makefiles and/or autotools.

• Difficulty

Medium.

• Potential mentors

Carlo de Falco, Marco Caliari, Jacopo Corno, Sebastian Schöps

Improve logm, sqrtm, funm

The goal here is to implement some missing Matlab functions related to matrix functions like the matrix exponential. There is a general discussion of the problem. A good starting point for available algorithms and open-source implementations is Higham and Deadman's "A Catalogue of Software for Matrix Functions".

• Required skills

Read and Write both C++ and Octave code, find and read research papers, research experience in numerical analysis, familiarity with analysis of algorithms.

• Difficulty

Difficult.

• Potential mentors

Jordi Gutiérrez Hermoso

Generalised eigenvalue problem

Certain calling forms of the eig function are currently missing, including preliminary balancing; computing left eigenvectors as a third output; returning eigenvalues as a vector instead of as a diagonal matrix; and choosing among generalized eigenvalue algorithms. See also this discussion.

• Required skills

C++; familiarity with numerical linear algebra and LAPACK.

• Difficulty

Medium.

• Potential mentor

Nir Krakauer

Improve iterative methods for sparse linear systems

GNU Octave currently has the following Krylov subspace methods for sparse linear systems: pcg (spd matrices) and pcr (Hermitian matrices), bicg, bicgstab, cgs, gmres, and qmr (general matrices). Their descriptions and their error messages are not aligned. Moreover, they have similar blocks of code (input check for instance) which can be written once and for all in common functions. The first step in this project could be a revision and a synchronization of the codes.

In Matlab, some additional methods are available: minres and symmlq (symmetric matrices), tfqmr and bicgstabl (generale matrices), lsqr (least squares). The second step in this project could be the implementation of some of these missing functions.

The reference book is available [www-users.cs.umn.edu/~saad/IterMethBook_2ndEd.pdf here]

• Required skills

Not yet listed.

• Difficulty

Not yet listed.

• Mentor

Marco Caliari, Carlo de Falco

Adding functionality to Forge packages

TISEAN package

TISEAN is a suite of code for nonlinear time series analysis. It has have been partially re-implemented as libre software. The objective is to integrate TISEAN as an octave package as it was done for the Control package. Lot has been completed but there is still work left to do.

There missing functions to do computations on spike trains, to simulate autoregresive models, to create specialized plots, etc. Do check the progress of the project to see if you are interested.

• Package help at source forge.
• Package repository at source forge.

• Required skills

m-file scripting, C, C++, and FORTRAN API knowledge.

• Difficulty

easy/medium

• Mentor

User:KaKiLa

Symbolic package

Octave's Symbolic package handles symbolic computing and other CAS tools. The main component of Symbolic is a pure m-file class "@sym" which uses the Python package SymPy to do (most of) the actual computations. The package aims to expose the full functionality of SymPy while also providing a high-level of compatibility with the Matlab Symbolic Math Toolbox. Currently, communication between Octave and Python is handled with a pipe (see "help popen2") and parsing text. However, this is fragile when things go wrong: for example, catching exceptions from Python is a bit ad hoc.

The main aim of this proposed project is to implement (or even better co-opt an existing) C++ oct-file interface that interacts with Python as a library, and e.g., deals gracefully with exceptions. This could either supplement the existing IPC or replace it altogether.

• Required skills

m-file scripting, C (for Python internals), C++ (for Octave internals), and Python

• Difficulty

easy/medium

• Mentor

Colin B. Macdonald

Interval package

The interval package provides several arithmetic functions with accurate and guaranteed error bounds. Its development started in the end of 2014 and there is some fundamental functionality left to be implemented. See the list of functions, basically any missing numeric Octave function could be implemented as an interval extension in the package. Potential projects:

• Implement missing algorithms (as m-files)—difficulty and whether knowledge in interval analysis is required depends on the particular function. Of course, you may use papers which present such algorithms.
• Improve existing algorithms (support more options for plotting, support more options for optimizers, increase accuracy, …)
• Make the package support N-dimensional arrays, this requires less knowledge of interval arithmetic but can be a rather exhaustive job since it affects most function files in the package

• Required skills

m-file scripting, basic knowledge of computer arithmetics (especially floating-point computations), interval analysis (depending on the functions to implement).

• Difficulty

Medium.

• Mentor

Oliver Heimlich

Mapping or Geometry package: Implement boolean operations on polygons

The goal is to implement a Matlab-compatible set of boolean operations and supporting function for acting on polygons. These include the standard set of potential operations such as union/OR, intersection/AND, difference/subtraction, and exclusiveor/XOR. There is already an octave-forge package that implements a large part of this (the octclip package); however that does not do XOR; processing polygons with holes could be done better; and maintainability is hampered because all code comments etc. are in Spanish. Other than that, octclip performs fine.

There are a variety of existing polygon libraries that implement much of the functionality and thus this would be incorporating the library into GNU Octave. The libraries with acceptable licenses are ClipperLib, Boost::Polygon, Boost::Geometry, or kbool. This would include implementing the following functions: polybool, ispolycw, poly2ccw, poly2cw, poly2fv, polyjoin, and polysplit. A partial implementation with ClipperLib and GPC can be found here.

• Required skills

Knowledge of C++; C; familiarity with boolean logic; polygons, windings, and geometry

• Difficulty

Easy to Medium.

• Potential mentor

John Swensen

Infrastructure

Octave Package management

Octave management of installed packages is performed by a single function, pkg, which does pretty much everything. This function has a few limitations which are hard to implement with the current codebase, and will most likely require a full rewrite.

The planned improvements are:

• support for multiple Octave installs
• support for multiple version packages
• support for system-wide and user installed packages
• automatic handling of dependencies
• more flexibility on dependencies, e.g., dependent on specific Octave build options or being dependent in one of multiple packages
• management of tests and demos in C++ sources of packages
• think ahead for multiple
• easily load or check specific package versions

The current pkg also performs some functions which probably should not. Instead a package for developers should be created with such tools.

Many of these problems have been solved in other languages. Familiarity with how other languages handle this problem will be useful to come up with elegant solutions. In some cases, there are standards to follow. For example, there are specifications published by freedesktop.org about where files should go (base directory spec) and Windows seems to have its own standards. See bugs #36477 and #40444 for more details.

In addition, package names may start to collide very easily. One horrible way to workaround this by is choosing increasingly complex package names that give no hint on the package purpose. A much better is option is providing an Authority category like Perl 6 does. Nested packages is also an easy way to provide packages for specialized subjects (think image::morphology). A new pkg would think all this things now, or allow their implementation at a later time. Read the unfinished plan for more details.

• Minimum requirements

Ability to read and write Octave code, experience with Octave packages, and understanding of the basics of autotools. The most important skill is software design.

• Difficulty

Easy to Medium.

• Mentor

Carnë Draug

Command line suggestion feature

Currently Octave has no mechanism for suggesting corrections to typographic errors on the command line. An autocomplete/suggestion function is provided (using the double-TAB shortcut), but recent discussions have indicated a desire for a more proactive measure to catch user error. Potential applicants are referred to bug #46881 regarding the usage of grey vs. gray.

Suggested improvements are:

• provide one or more suggested corrections to the user when a command line entry produces an error.
• recognition and suggested correction for apparent syntax errors
• function suggestion(s) when a 'close' match is found (close remains to be defined)
• multiple suggestions if more than one option seems likely, along with a user-friendly method of selecting the appropriate choice.
• user selectable option to disable and/or customize the suggestion behavior
• correct operation, or graceful degradation, whether Octave is run in GUI or command-line mode.

As mentioned in the bug #46881 discussion, this project has little-to-no relation to m-code compatibility. As such, emulation of the behavior of other software is not required, nor even necessarily desired. Octave is free to implement as simple or complex a solution to this feature request as is necessary to provide the best experience to the user. There may be tools, features, or code from other license-compatible projects that can be of use here, and the applicant would be encouraged to identify and leverage such resources as appropriate.

• Minimum requirements

TBD

• Difficulty

Easy to Medium.

• Mentor

Undetermined

Image Analysis

Improvements to N-dimensional image processing

The image package has partial functionality for N-dimensional images. These images exist for example in medical imaging where slices from scans are assembled to form anatomical 3D images. If taken over time and at different laser wavelengths or light filters, they can also result in 5D images. Albeit less common, images with even more dimensions also exist. However, their existence is irrelevant since most of the image processing operations are mathematical operations which are independent of the number of dimensions.

As part of GSoC 2013, the core functions for image IO, imwrite and imread, were extended to better support this type of images. Likewise, many functions in the image package, mostly morphology operators, were expanded to deal with this type of image. Since then, many other functions have been improved, sometimes completely rewritten, to abstract from the number of dimensions. In a certain way, supporting ND images is also related to choosing good algorithms since such large images tend to be quite large.

This project will continue on the previous work, and be mentored by the previous GSoC student and current image package maintainer. Planning the project requires selection of functions lacking ND support and identifying their dependencies. For example, supporting imclose and imopen was better implemented by supporting imerode and imdilate which then propagated ND support to all of its dependencies. These dependencies need to be discovered first since often they are not being used yet, and may even be missing function. This project can also be about implementing functions that have not yet been implemented. Also note that while some functions in the image package will accept ND images as input, they are actually not correctly implemented and will give incorrect results.

• Required skills

m-file scripting, and a fair amount of C++ since a lot of image analysis cannot be vectorized. Familiarity with common CS algorithms and willingness to read literature describing new algorithms will be useful.

• Difficulty

Difficult.

• Potential mentor

Carnë Draug

Improve Octave's image IO

There are a lot of image formats. To handle this, Octave uses GraphicsMagic (GM), a library capable of handling a lot of them in a single C++ interface. However, GraphicsMagick still has its limitations. The most important are:

• GM has build option quantum which defines the bitdepth to use when reading an image. Building GM with high quantum means that images of smaller bitdepth will take a lot more memory when reading, but building it too low will make it impossible to read images of higher bitdepth. It also means that the image needs to always be rescaled to the correct range.
• GM supports unsigned integers only thus incorrectly reading files such as TIFF with floating point data
• GM hides away details of the image such as whether the image file is indexed. This makes it hard to access the real data stored on file.

This project would implement better image IO for scientific file formats while leaving GM handle the others. Since TIFF is the de facto standard for scientific images, this should be done first. Among the targets for the project are:

• implement the Tiff class which is a wrap around libtiff, using classdef. To avoid creating too many private __oct functions, this project could also create a C++ interface to declare new Octave classdef functions.
• improve imread, imwrite, and imfinfo for tiff files using the newly created Tiff class
• port the bioformats into Octave and prepare a package for it
• investigate other image IO libraries
• clean up and finish the dicom package to include into Octave core
• prepare a matlab compatible implementation of the FITS package for inclusion in Octave core

• Required skills

Knowledge of C++ and C since most libraries are written in those languages.

• Difficulty

Medium.

• Potential mentor

Carnë Draug