The following bug exists also as sourceforge bug request: [ 778394 ] GraphViz Interface boost version is 1.30.0 Because Jeremy seems to be reactivated and the sourceforge tracker status is still 'open' a small reminder: For an adjacency list of the following form adjacency_list write_graphviz produces the following graph structure --- output begin --- graph G { graph [splines=false bgcolor=lightgrey] node [shape=circle color=red] edge [style=solid] 002F48A0[label ="", height="0.1", pos="540,250"]; 002F4978[label ="", height="0.1", pos="278,321"]; 002F4A50[label ="", height="0.1", pos="198,67"]; 002F4B28[label ="", height="0.1", pos="163,27"]; 002F4C00[label ="", height="0.1", pos="442,487"]; 002F4B28--002F4A50 ; 002F4A50--002F4978 ; 002F4978--002F4B28 ; 002F4B28--002F48A0 ; 002F48A0--002F4A50 ; 002F4978--002F48A0 ; 002F48A0--002F4C00 ; 002F4C00--002F4978 ; } --- output end --- This causes error messages from neato (GraphViz tool): --- error messages begin -- v:\my\delaunay\test\d1\output>neato -s72 -n2 -Tgif -o file.gif delaunay.dot Warning: delaunay.dot:5: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:6: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:7: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:8: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:9: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:10: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:10: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:11: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:11: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:12: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:12: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:13: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:13: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:14: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:14: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:15: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:15: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:16: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:16: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:17: ambiguous "002F" splits into two names: "002" and "F" Warning: delaunay.dot:17: ambiguous "002F" splits into two names: "002" and "F" Error: node 002 in graph G has no position as required by the -n flag v:\my\delaunay\test\d1\output> --- error messages end --- The reason can be found at: http://www.research.att.com/~erg/graphviz/info/lang.html "An ID is any string of alphabetic characters, underscores or digits, but not beginning with a digit; or a number; or any quoted string possibly containing escaped quotes." So, the hexadecimal number (mix of digits and characters) of the transfered pointer (list item) is the problem.I would suggest write_graph_viz quotes the node name or prefixes with a character or uses a decimal representation. Regards, Micha