/// <summary>
/// Propose to map ivtx1 from the first graph to ivtx2 in the second for
/// the isomorphism being formed
/// </summary>
/// <param name="ivtx1">Vertex index in the first graph</param>
/// <param name="ivtx2">Vertex index in the second graph</param>
/// <param name="vfs">State determining the isomorphism</param>
internal void SetMatch(int ivtx1, int ivtx2, VfState <TVAttr, TEAttr> vfs)
{
// Add both vertices to the "In Mapping" group
MoveToGroup(1, ivtx1, Group.ContainedInMapping, vfs);
MoveToGroup(2, ivtx2, Group.ContainedInMapping, vfs);
// Actually set the vertices to correspond in the isomorphism
vfs.SetIsomorphic(ivtx1, ivtx2);
// Add actions to undo this act...
AddAction(new BacktrackAction(Action.DeleteMatch, 1, ivtx1));
AddAction(new BacktrackAction(Action.DeleteMatch, 2, ivtx2));
}