void initFlowTest()

 {

   DIGRAPH_TYPEDEFS(SmartDigraph);

   SmartDigraph g;

   SmartDigraph::ArcMap<int> cap(g),iflow(g);

   Node s=g.addNode(); Node t=g.addNode();

   Node n1=g.addNode(); Node n2=g.addNode();

   Arc a;

   a=g.addArc(s,n1); cap[a]=20; iflow[a]=20;

   a=g.addArc(n1,n2); cap[a]=10; iflow[a]=0;

   a=g.addArc(n2,t); cap[a]=20; iflow[a]=0;

   Preflow<SmartDigraph> pre(g,cap,s,t);

   pre.init(iflow);

   pre.startFirstPhase();

   check(pre.flowValue() == 10, "The incorrect max flow value.");

   check(pre.minCut(s), "Wrong min cut (Node s).");

   check(pre.minCut(n1), "Wrong min cut (Node n1).");

   check(!pre.minCut(n2), "Wrong min cut (Node n2).");

   check(!pre.minCut(t), "Wrong min cut (Node t).");

 }

   initFlowTest();