news
Friday 03 July 2009: Algebraic expression of invariants
The use of algebraic expressions of invariants to define coordinates and conditions was limited to the console version of GraPHedron. It is no more the case: you can now use them also via the website.
Saturday 18 April 2009: Reopening of GraPHedron
The GraPHedron web site was closed due to an hardware failure. Hopefully, all databases were restored. However, your old projects should be recomputed if you need the reports again. It can be easily done in your existing projects page. Also, some invariants are not yet available since the server is currently computing them.
Friday 26 October 2007: The paper explaining the principles of GraPHedron is available
The paper Facet defining inequalities among graph invariants: the system GraPHedron to appear in Discrete Applied Mathematics is now available online. You can download it via ScienceDirect.
Monday 23 April 2007: Lemon C++ Library allowed in invariant's implementation
You can now request a new invariant providing an implementation which uses the Lemon C++ library version 0.6 (Library of Efficient Models and Optimization in Networks) in the ask new invariant page.
Such requests can be very quickly treated as their implementations can be directly added to the system.
Moreover, this library is very efficient and intended to grow quickly.Friday 30 March 2007: Real invariants allowed
You can now use invariants with real values (often from spectral or chemical graph theory, see the list of real invariants).
However, you have to be aware that in this case:
- computation is approximated (floating point arithmetic)
- the number of polytope's vertices can be huge (it can be useful to deselect thepoint's distribution
option)Friday 30 March 2007: Asking new invariants
You can now submit requests for new invariants (when logged).
Tuesday 27 March 2007: New invariants added
There are 4 new boolean invariants (available only if you use trees as generated graphs): centered / bicentered and centroidal / bicentroidal. There is also a new integer invariant: the indecomposability index. All these invariants were suggested for addition (and the latter also conceived) by N.J.A. Sloane.
Tuesday 27 March 2007: Default options for new projects
When creating a new project, two options -- considered as useful in many cases -- are now selected by default:
- Drawing of the point's distribution inside the polytopes and computation of Pareto points
- Graph's nodes are colored such that all nodes with a given degree have the same color (useful for characterization)
report
andcomputation
option's tabs.Monday 19 February 2007: Official opening of the site
This web interface for GraPHedron is now officially opened. We will be very pleased if you send any feedback to improve it. Thank you for your cooperation.
We hope that you will find interesting results with the help of GraPHedron.Wednesday 14 February 2007: GraPHedron's online bibliography
The online bibliography is now available. Please help us to keep it up-to date.
Thursday 11 January 2007: List of invariants
You can now download a PDF file with the list of available invariants and their definitions, in the submenu Invariant's information of the Invariants and graph's classes menu (available only when logged).
Friday 22 December 2006: The GraPHedron web portal is open for testing
This web site is now open for the test phase. Please feel free to make any suggestions and/or corrections. Thank you for your help.
