Hi, I am new here. I recently downloaded the boost library from www.boost.org. I need to use the "subgraph" function in the library. I tried to run the example file "subgraph.cpp", but the running result was different from what was given in the file. Below is my running result and sample output: //my result: G0: 0 --> 1 1 --> 2 3 2 --> 5 3 --> 4 --> 1 5 5 --> 3 0(0,1) 1(1,2) 2(1,3) 6(2,5) 3(4,1) 4(4,5) 5(5,3) G1: 0 --> 2 1 --> 2 2 --> 6(0,2) 4(1,2) G2: 0 --> 1 1 --> 0(0,1) //sample output G0: 0 --> 1 1 --> 2 3 2 --> 5 3 --> 4 --> 1 5 5 --> 3 0(0,1) 1(1,2) 2(1,3) 6(2,5) 3(4,1) 4(4,5) 5(5,3) G1: 2 --> 5 4 --> 5 5 --> 6(2,5) 4(4,5) G2: 0 --> 1 1 --> 0(0,1) //====================================================== Basically what happened was that the vertex indices of the subgraph G1 in my output are child's local indices, however, the vertex indices of the subgraph G1 in the sample output is parent's global indices. Can somebody explain this? Is it a bug in the boost code? Thanks very much, Qiaofeng