OpenRCE Blog Entry

Ero Carrera (ero) <ero

carrera

gmail

com>

Thursday, February 14 2008 23:53.00 CST

Finally! it was long due. Here it is pydot 1.0.2

Some weeks ago I started updating the code to support all the attributes and enhancements in GraphViz 2.16. In attempting to make it pass all the regression tests some severe shortcomings it had became apparent.
pydot users had also provided with insight into how to improve performance by redesigning the way the data for the objects is stored internally. All in all, the limitations I was facing led me to rewrite the whole core of pydot, which took much longer than I wanted but I feel it was well worth it as its orders of magnitude better than the last release 0.9.

Performance-wise the new pydot stores graphs and their objects using a hierarchy of nested dictionaries and lists. Graph, Node, Edge objects are mere proxies to the data and are created on demand. So that now its possible to have a graph with a 1 million edges and there will not be a single Edge instance (only if requested, then they will be created on demand, mapping the data and providing with all the methods to act on the data in the global dictionary).
Storing a graph with 1 million edges in pydot 1.0 has approximately the same memory requirements (~813MiB) as dealing with one with only 40.000 edges in pydot 0.9 (~851MiB), the 40.000 edges graph needs ~35MiB in pydot 1.0 . Handling graphs should be much faster, as no linear searches are performed in pydot 1.0.2