Created 3 Nov 2001 at 09:51 UTC by pom, last modified 7 May 2002 at 08:46 UTC by pom.

Homepage: http://pigale.sourceforge.net/Freshmeat page: http://freshmeat.net/projects/pigale/

**Notes:**

We develop a **graph editor** and a **C++ **algorithm library essentially concerned with planar graphs. The editor is particularly intended for graph theoretical research.

Pigale is available under the **GPL** License and can be obtained either by ftp or cvs.

It is built over a new graph data structure optimizing topological operations on static graphs.

The library includes the following new algorithms based on recent theoretical researches of our site.

- General Algorithms:
- a planarity test and an embedding computation algorithm using Fraysseix-Rosenstiehl left-right algorithm.
- a linear time algorithm to locate a Kuratowski subdivision or a cotree critical partial subgraph in a non planar graph,
- a linear time 3-connexity test for planar graphs,
- a linear time recognition algorithm for subdivisions of 3-connected planar graphs,
- a linear time 4-connexity test for maximal planar graphs,
- a linear time optimal triangulation algorithm for 3-connected planar graphs,
- a fast Depth-First Search algorithm,
- fast bipolar and regular orientation algorithms for planar graphs,
- a linear time algorithm for biconnecting planar graphs while preserving the embedding, which increases the degrees by at most 6 (optimal),
- a linear time triangulation algorithm for 3-connected planar graphs increasing the degrees by at most 6 (optimal),
- a partitioner algorithm based on factorial analysis.

- Drawing Algorithms:
- optimized Fary drawing algorithms relying on new planar augmentation algorithms, i.e.:
- Schnyder algorithm using our triangulation algorithms,
- Schnyder algorithm using a vertex triangulation,
- Tutte barycentric representation of 3-connected graphs,
- A Fary representation derived from the Tutte algorithm,

- an algorithm to represent 2-connected planar bipartite graphs by drawing two forests on two pages,
- an algorithm to represent 2-connected planar bipartite graphs as the incidence graph of horizontal and vertical segments,
- An algorithm to represent a graph in
**R**3, as projections of different embeddings of the graph in**R**n-1.

- optimized Fary drawing algorithms relying on new planar augmentation algorithms, i.e.:
- Experimental Algorithms:
- an heuristic to detect symmetries,
- an heuristic to find a maximal planar partial graph of a non planar graph.

License: GPL

This project has the following developers:

**New HTML Parser**: The long-awaited libxml2 based HTML parser
code is live. It needs further work but already handles most
markup better than the original parser.

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If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!