This repository is a collection of problems.
Each problem is a subproject managed by a subproject developer. Anybody
is invited to submit a new problem. Anybody is invited to contribute to
enrich any problem in the repository.

The purpose of a subproject is to study different aspects of a problem
leaving interesting or useful traces.

There are (among others) various justifications to keep a trace: it
illustrates some particular property of the used solver, it
clearly shows the way to solve the problem, it presents best analysis potential
of some analysis tool. It may also illustrate some characteristics
of the problem or of its resolution which help to reach or to improve the
solutions.; it may also help to find some modelling or programming mistake
(using some solver and tool).

Each subproject/problem shall follow a project schema described here (to be done). To start a new project/program, prepare a first instance of the project, then contact one of the project administrator.

- illustrative problems : (pedagogical problems used to help understanding aspects of solvers, resolution or tools)
- classical problems (mostly academic problems, including open instances, in order to find the best ways to observe resolution and find solutions)
- practical application problems : (practical problems, not necessarily big, with the objective to show practical usefulness of tools)

- to find a bug (wrong, under or over constrained program). In this case incorrect programs may also be studied in a project whatever the cathegory it belongs.
- to improve resolution or to scale the program, showing how the used tool and the kind of observation must be modified when the instances grow.
- any objective which shows the usefulness of the tools for some purpose, provided this objective can be comprehensively presented.