Edge Boundary Determination

I have a surface which is defined by around 50000 triangular facets. Is there a way of determining which edges are free ie not connected to any other edges?

Many thanks

Build an edge list and compare each edge against every other. This kind of thing tends to be expensive but you can speed it up by using a hash table to store the edges, that way you need only test edges that share certain properties (typically spatial properties). In your case it may be indexed in which case the hashing and checking is trivial.