Dear Group, trying for several days, I simply don't get the correct usage of internal property maps and the connected_components algorithm. My graphs are very large (about 600 000 vertices), so that I am using internal instead of external property maps. Looking at one of Jeremy's postings (http://lists.boost.org/MailArchives/boost/msg15114.php) I defined my graph as follows: namespace boost { enum vertex_component_t {vertex_component = 113 }; BOOST_INSTALL_PROPERTY(vertex, component); } typedef typename boost::adjacency_list< boost::listS, //edges boost::listS, //nodes boost::undirectedS, //vertex properties boost::property<boost::vertex_name_t, std::string, //the name of the protein boost::property<boost::vertex_component_t, int > > > // no edge properties > Graph; The code that uses internal property maps as an argument to compute_components comes below (actually, I am not sure whether this is a connected_components problem at all). typedef boost::property_map<Graph, boost::vertex_component_t>::type ComponentPropertyMap; ComponentPropertyMap component = boost::get(boost::vertex_component,g); int components_num = boost::connected_components(g,component); This looks quite straightforward and is in line with what Jeremy has posted. But I get the following compiler errors (using Boost 1.29 and gcc 3.2): [snip] /project/algorithmics/include/boost/property_map.hpp:344: no match for `const __gnu_cxx::__normal_iterator<boost::default_color_type*, std::vector<boost::default_color_type, std::allocator<boost::default_color_type> > >& + const boost::detail::error_property_not_found&' operator What is going wrong? Do I have to use a color_type_t (Why? How?)? Any help is very welcome... Many thanks in advance Martin -- ----------------------------------------------------------------------------- Martin Okrslar MPI for Molecular Genetics phone: ++ 49 + 30 / 8413-1166 Computational Molecular Biology Fax: ++ 49 + 30 / 8413-1152 Ihnestrasse 73 email: okrslar@molgen.mpg.de D-14195 Berlin URL: http://cmb.molgen.mpg.de -----------------------------------------------------------------------------