stack 'active' on the active nodes on level i implemented by hand

  stack 'active' on the active nodes on level i

 Parameters H0 and H1 are initialized to 20 and 10.

 Parameters H0 and H1 are initialized to 20 and 1.

      minimum min cut. M should be a map of bools initialized to false.

      minimum min cut. M should be a map of bools initialized to false. ??Is it OK?

     typedef typename std::vector<std::stack<Node> > VecStack;

     typedef typename Graph::template NodeMap<Node> NNMap;

     typedef typename std::vector<Node> VecNode;

     const CapMap& capacity;  

     CapMap* capacity;  

     FlowMap& flow;

     FlowMap* flow;

     T value;

     int n;      //the number of nodes of G

     bool constzero;

     typename Graph::template NodeMap<int> level;      

     typename Graph::template NodeMap<T> excess; 

 	    FlowMap& _flow, bool _constzero ) :

 	    FlowMap& _flow) :

       G(_G), s(_s), t(_t), capacity(_capacity), flow(_flow), constzero(_constzero) {}

       G(_G), s(_s), t(_t), capacity(&_capacity), 

       flow(&_flow), n(_G.nodeNum()), level(_G), excess(_G,0) {}

     void run() {

       preflow( ZERO_FLOW );

     }

     void preflow( flowEnum fe ) {

     void run() {

       preflowPhase0(fe);

       preflowPhase1();

       value=0;                //for the subsequent runs

     }

       bool phase=0;        //phase 0 is the 1st phase, phase 1 is the 2nd

     void preflowPhase0( flowEnum fe ) {

       int n=G.nodeNum(); 

       /*

       //It is 0 in case 'bound decrease' and 1 in case 'highest label'

 	what_heur is 0 in case 'bound decrease' 

 	and 1 in case 'highest label'

       */

       /*

       //Needed for 'bound decrease', true means no active nodes are above bound b.

 	Needed for 'bound decrease', 'true'

 	means no active nodes are above bound b.

       */

       int relabel=0;

       typename Graph::template NodeMap<int> level(G,n);      

       VecStack active(n);

       typename Graph::template NodeMap<T> excess(G); 

       NNMap left(G,INVALID);

       std::vector<Node> active(n-1,INVALID);

       NNMap right(G,INVALID);

       typename Graph::template NodeMap<Node> next(G,INVALID);

       VecNode level_list(n,INVALID);

       //Stack of the active nodes in level i < n.

       //List of the nodes in level i<n, set to n.

       //We use it in both phases.

       NodeIt v;

       typename Graph::template NodeMap<Node> left(G,INVALID);

       for(G.first(v); G.valid(v); G.next(v)) level.set(v,n);

       typename Graph::template NodeMap<Node> right(G,INVALID);

       //setting each node to level n

       std::vector<Node> level_list(n,INVALID);

       /*

       switch ( fe ) {

 	List of the nodes in level i<n.

       case PREFLOW:

       */

 	{

 	  //counting the excess

 	  NodeIt v;

       if ( constzero ) {

 	  for(G.first(v); G.valid(v); G.next(v)) {

 	    T exc=0;

 	/*Reverse_bfs from t, to find the starting level.*/

 	level.set(t,0);

 	    InEdgeIt e;

 	std::queue<Node> bfs_queue;

 	    for(G.first(e,v); G.valid(e); G.next(e)) exc+=(*flow)[e];

 	bfs_queue.push(t);

 	    OutEdgeIt f;

 	    for(G.first(f,v); G.valid(f); G.next(f)) exc-=(*flow)[f];

 	while (!bfs_queue.empty()) {

 	    excess.set(v,exc);	  

 	  Node v=bfs_queue.front();	

 	  bfs_queue.pop();

 	    //putting the active nodes into the stack

 	  int l=level[v]+1;

 	    int lev=level[v];

 	    if ( exc > 0 && lev < n && v != t ) active[lev].push(v);

 	  }

 	  break;

 	}

       case GEN_FLOW:

 	{

 	  //Counting the excess of t

 	  T exc=0;

 	  for(G.first(e,v); G.valid(e); G.next(e)) {

 	  for(G.first(e,t); G.valid(e); G.next(e)) exc+=(*flow)[e];

 	    Node w=G.tail(e);

 	  OutEdgeIt f;

 	    if ( level[w] == n && w != s ) {

 	  for(G.first(f,t); G.valid(f); G.next(f)) exc-=(*flow)[f];

 	      bfs_queue.push(w);

 	      Node first=level_list[l];

 	  excess.set(t,exc);	

 	      if ( G.valid(first) ) left.set(first,w);

 	      right.set(w,first);

 	  break;

 	      level_list[l]=w;

 	      level.set(w, l);

 	    }

 	  }

 	}

 	//the starting flow

 	OutEdgeIt e;

 	for(G.first(e,s); G.valid(e); G.next(e)) 

 	{

 	  T c=capacity[e];

 	  if ( c == 0 ) continue;

 	  Node w=G.head(e);

 	  if ( level[w] < n ) {	  

 	    if ( excess[w] == 0 && w!=t ) {

 	      next.set(w,active[level[w]]);

 	      active[level[w]]=w;

 	    }

 	    flow.set(e, c); 

 	    excess.set(w, excess[w]+c);

 	  }

       else 

       {

       preflowPreproc( fe, active, level_list, left, right );

       //End of preprocessing 

 	/*

 	  Reverse_bfs from t in the residual graph, 

 	  to find the starting level.

       //Push/relabel on the highest level active nodes.

 	*/

 	level.set(t,0);

 	std::queue<Node> bfs_queue;

 	bfs_queue.push(t);

 	while (!bfs_queue.empty()) {

 	  Node v=bfs_queue.front();	

 	  bfs_queue.pop();

 	  int l=level[v]+1;

 	  InEdgeIt e;

 	  for(G.first(e,v); G.valid(e); G.next(e)) {

 	    if ( capacity[e] == flow[e] ) continue;

 	    Node w=G.tail(e);

 	    if ( level[w] == n && w != s ) {

 	      bfs_queue.push(w);

 	      Node first=level_list[l];

 	      if ( G.valid(first) ) left.set(first,w);

 	      right.set(w,first);

 	      level_list[l]=w;

 	      level.set(w, l);

 	    }

 	  }

 	  OutEdgeIt f;

 	  for(G.first(f,v); G.valid(f); G.next(f)) {

 	    if ( 0 == flow[f] ) continue;

 	    Node w=G.head(f);

 	    if ( level[w] == n && w != s ) {

 	      bfs_queue.push(w);

 	      Node first=level_list[l];

 	      if ( G.valid(first) ) left.set(first,w);

 	      right.set(w,first);

 	      level_list[l]=w;

 	      level.set(w, l);

 	    }

 	  }

 	}

 	/*

 	  Counting the excess

 	*/

 	NodeIt v;

 	for(G.first(v); G.valid(v); G.next(v)) {

 	  T exc=0;

 	  InEdgeIt e;

 	  for(G.first(e,v); G.valid(e); G.next(e)) exc+=flow[e];

 	  OutEdgeIt f;

 	  for(G.first(f,v); G.valid(f); G.next(f)) exc-=flow[e];

 	  excess.set(v,exc);	  

 	  //putting the active nodes into the stack

 	  int lev=level[v];

 	  if ( exc > 0 && lev < n ) {

 	    next.set(v,active[lev]);

 	    active[lev]=v;

 	  }

 	}

 	//the starting flow

 	OutEdgeIt e;

 	for(G.first(e,s); G.valid(e); G.next(e)) 

 	{

 	  T rem=capacity[e]-flow[e];

 	  if ( rem == 0 ) continue;

 	  Node w=G.head(e);

 	  if ( level[w] < n ) {	  

 	    if ( excess[w] == 0 && w!=t ) {

 	      next.set(w,active[level[w]]);

 	      active[level[w]]=w;

 	    }

 	    flow.set(e, capacity[e]); 

 	    excess.set(w, excess[w]+rem);

 	  }

 	}

 	InEdgeIt f;

 	for(G.first(f,s); G.valid(f); G.next(f)) 

 	{

 	  if ( flow[f] == 0 ) continue;

 	  Node w=G.head(f);

 	  if ( level[w] < n ) {	  

 	    if ( excess[w] == 0 && w!=t ) {

 	      next.set(w,active[level[w]]);

 	      active[level[w]]=w;

 	    }

 	    excess.set(w, excess[w]+flow[f]);

 	    flow.set(f, 0); 

 	  }

 	}

       }

       /* 

 	 End of preprocessing 

       */

       /*

 	Push/relabel on the highest level active nodes.

       */	

 	  } else {

 	  } else break;

 	    phase=1;

 	}

 	    level.set(s,0);

 	    std::queue<Node> bfs_queue;

 	if ( active[b].empty() ) --b; 

 	    bfs_queue.push(s);

 	    while (!bfs_queue.empty()) {

 	      Node v=bfs_queue.front();	

 	      bfs_queue.pop();

 	      int l=level[v]+1;

 	      InEdgeIt e;

 	      for(G.first(e,v); G.valid(e); G.next(e)) {

 		if ( capacity[e] == flow[e] ) continue;

 		Node u=G.tail(e);

 		if ( level[u] >= n ) { 

 		  bfs_queue.push(u);

 		  level.set(u, l);

 		  if ( excess[u] > 0 ) {

 		    next.set(u,active[l]);

 		    active[l]=u;

 		  }

 		}

 	      }

 	      OutEdgeIt f;

 	      for(G.first(f,v); G.valid(f); G.next(f)) {

 		if ( 0 == flow[f] ) continue;

 		Node u=G.head(f);

 		if ( level[u] >= n ) { 

 		  bfs_queue.push(u);

 		  level.set(u, l);

 		  if ( excess[u] > 0 ) {

 		    next.set(u,active[l]);

 		    active[l]=u;

 		  }

 		}

 	      }

 	    }

 	    b=n-2;

 	    }

 	}

 	if ( !G.valid(active[b]) ) --b; 

 	  Node w=active[b].top();

 	  Node w=active[b];

 	  active[b].pop();

 	  active[b]=next[w];

 	  int newlevel=push(w,active);

 	  int lev=level[w];

 	  if ( excess[w] > 0 ) relabel(w, newlevel, active, level_list, 

 	  T exc=excess[w];

 				       left, right, b, k, what_heur);

 	  int newlevel=n;       //bound on the next level of w

 	  ++numrelabel; 

 	  OutEdgeIt e;

 	  if ( numrelabel >= heur ) {

 	  for(G.first(e,w); G.valid(e); G.next(e)) {

 	    numrelabel=0;

 	    if ( what_heur ) {

 	    if ( flow[e] == capacity[e] ) continue; 

 	      what_heur=0;

 	    Node v=G.head(e);            

 	      heur=heur0;

 	    //e=wv	    

 	      end=false;

 	    } else {

 	    if( lev > level[v] ) {      

 	      what_heur=1;

 	      /*Push is allowed now*/

 	      heur=heur1;

 	      b=k; 

 	    }

 	  }

 	} 

       } 

     }

     void preflowPhase1() {

       int k=n-2;  //bound on the highest level under n containing a node

       int b=k;    //bound on the highest level under n of an active node

       VecStack active(n);

       level.set(s,0);

       std::queue<Node> bfs_queue;

       bfs_queue.push(s);

       while (!bfs_queue.empty()) {

 	Node v=bfs_queue.front();	

 	bfs_queue.pop();

 	int l=level[v]+1;

 	      if ( excess[v]==0 && v!=t && v!=s ) {

 	InEdgeIt e;

 		int lev_v=level[v];

 	for(G.first(e,v); G.valid(e); G.next(e)) {

 		next.set(v,active[lev_v]);

 	  if ( (*capacity)[e] == (*flow)[e] ) continue;

 		active[lev_v]=v;

 	  Node u=G.tail(e);

 	      }

 	  if ( level[u] >= n ) { 

 	    bfs_queue.push(u);

 	      T cap=capacity[e];

 	    level.set(u, l);

 	      T flo=flow[e];

 	    if ( excess[u] > 0 ) active[l].push(u);

 	      T remcap=cap-flo;

 	  }

 	}

 	      if ( remcap >= exc ) {       

 		/*A nonsaturating push.*/

 	OutEdgeIt f;

 	for(G.first(f,v); G.valid(f); G.next(f)) {

 		flow.set(e, flo+exc);

 	  if ( 0 == (*flow)[f] ) continue;

 		excess.set(v, excess[v]+exc);

 	  Node u=G.head(f);

 		exc=0;

 	  if ( level[u] >= n ) { 

 		break; 

 	    bfs_queue.push(u);

 	    level.set(u, l);

 	      } else { 

 	    if ( excess[u] > 0 ) active[l].push(u);

 		/*A saturating push.*/

 	  }

 	}

 		flow.set(e, cap);

       }

 		excess.set(v, excess[v]+remcap);

       b=n-2;

 		exc-=remcap;

 	      }

       while ( true ) {

 	    } else if ( newlevel > level[v] ){

 	      newlevel = level[v];

 	if ( b == 0 ) break;

 	    }	    

 	if ( active[b].empty() ) --b; 

 	  } //for out edges wv 

 	else {

 	  Node w=active[b].top();

 	  active[b].pop();

 	if ( exc > 0 ) {	

 	  int newlevel=push(w,active);	  

 	  InEdgeIt e;

 	  for(G.first(e,w); G.valid(e); G.next(e)) {

 	  //relabel

 	  if ( excess[w] > 0 ) {

 	    if( flow[e] == 0 ) continue; 

 	    Node v=G.tail(e);  

 	    //e=vw

 	    if( lev > level[v] ) {  

 	      /*Push is allowed now*/

 	      if ( excess[v]==0 && v!=t && v!=s ) {

 		int lev_v=level[v];

 		next.set(v,active[lev_v]);

 		active[lev_v]=v;

 	      }

 	      T flo=flow[e];

 	      if ( flo >= exc ) { 

 		/*A nonsaturating push.*/

 		flow.set(e, flo-exc);

 		excess.set(v, excess[v]+exc);

 		exc=0;

 		break; 

 	      } else {                                               

 		/*A saturating push.*/

 		excess.set(v, excess[v]+flo);

 		exc-=flo;

 		flow.set(e,0);

 	      }  

 	    } else if ( newlevel > level[v] ) {

 	      newlevel = level[v];

 	    }	    

 	  } //for in edges vw

 	} // if w still has excess after the out edge for cycle

 	excess.set(w, exc);

 	/*

 	  Relabel

 	*/

 	if ( exc > 0 ) {

 	  //now 'lev' is the old level of w

 	  if ( phase ) {

 	    next.set(w,active[newlevel]);

 	    active[newlevel].push(w);

 	    active[newlevel]=w;

 	  } else {

 	  }

 	    //unlacing starts

 	    Node right_n=right[w];

 	    Node left_n=left[w];

 	    if ( G.valid(right_n) ) {

 	      if ( G.valid(left_n) ) {

 		right.set(left_n, right_n);

 		left.set(right_n, left_n);

 	      } else {

 		level_list[lev]=right_n;   

 		left.set(right_n, INVALID);

 	      } 

 	    } else {

 	      if ( G.valid(left_n) ) {

 		right.set(left_n, INVALID);

 	      } else { 

 		level_list[lev]=INVALID;   

 	      } 

 	    } 

 	    //unlacing ends

 	    if ( !G.valid(level_list[lev]) ) {

 	       //gapping starts

 	      for (int i=lev; i!=k ; ) {

 		Node v=level_list[++i];

 		while ( G.valid(v) ) {

 		  level.set(v,n);

 		  v=right[v];

 		}

 		level_list[i]=INVALID;

 		if ( !what_heur ) active[i]=INVALID;

 	      }	     

 	      level.set(w,n);

 	      b=lev-1;

 	      k=b;

 	      //gapping ends

 	    } else {

 	      if ( newlevel == n ) level.set(w,n); 

 	      else {

 		level.set(w,++newlevel);

 		next.set(w,active[newlevel]);

 		active[newlevel]=w;

 		if ( what_heur ) b=newlevel;

 		if ( k < newlevel ) ++k;      //now k=newlevel

 		Node first=level_list[newlevel];

 		if ( G.valid(first) ) left.set(first,w);

 		right.set(w,first);

 		left.set(w,INVALID);

 		level_list[newlevel]=w;

 	      }

 	    }

 	    ++relabel; 

 	    if ( relabel >= heur ) {

 	      relabel=0;

 	      if ( what_heur ) {

 		what_heur=0;

 		heur=heur0;

 		end=false;

 	      } else {

 		what_heur=1;

 		heur=heur1;

 		b=k; 

 	      }

 	    }

 	  } //phase 0

 	} // if ( exc > 0 )

     }

       value = excess[t];

       /*Max flow value.*/

     //Returns the maximum value of a flow.

     } //void run()

     /*

       Returns the maximum value of a flow.

      */

       return value;

       return excess[t];

     }

     }

     //should be used only between preflowPhase0 and preflowPhase1

     FlowMap Flow() {

     template<typename _CutMap>

       return flow;

     void actMinCut(_CutMap& M) {

       }

     void Flow(FlowMap& _flow ) {

       for(G.first(v) ; G.valid(v); G.next(v))

       for(G.first(v); G.valid(v); G.next(v)) 

 	_flow.set(v,flow[v]);

 	if ( level[v] < n ) M.set(v,false);

 	else M.set(v,true);

 	  if (!M[v] && flow[e] < capacity[e] ) {

 	  if (!M[v] && (*flow)[e] < (*capacity)[e] ) {

 	  if (!M[v] && flow[f] > 0 ) {

 	  if (!M[v] && (*flow)[f] > 0 ) {

       NodeIt v;

       for(G.first(v) ; G.valid(v); G.next(v)) {

 	M.set(v, true);

       }

       M.set(t,true);        

       M.set(t,false);        

 	  if (!M[v] && flow[e] < capacity[e] ) {

 	  if (M[v] && (*flow)[e] < (*capacity)[e] ) {

 	    M.set(v, true);

 	    M.set(v, false);

 	  if (!M[v] && flow[f] > 0 ) {

 	  if (M[v] && (*flow)[f] > 0 ) {

 	    M.set(v, true);

 	    M.set(v, false);

     }

       NodeIt v;

       for(G.first(v) ; G.valid(v); G.next(v)) {

 	M.set(v, !M[v]);

       }

     }

     void reset_target (Node _t) {t=_t;}

     void resetTarget (const Node _t) {t=_t;}

     void reset_source (Node _s) {s=_s;}

     void resetSource (const Node _s) {s=_s;}

     template<typename _CapMap>   

     void resetCap (const CapMap& _cap) {

     void reset_cap (_CapMap _cap) {capacity=_cap;}

       capacity=&_cap;

     }

     template<typename _FlowMap>   

     void reset_cap (_FlowMap _flow, bool _constzero) {

     void resetFlow (FlowMap& _flow) {

       flow=_flow;

       flow=&_flow;

       constzero=_constzero;

     }

     }

   private:

     int push(const Node w, VecStack& active) {

       int lev=level[w];

       T exc=excess[w];

       int newlevel=n;       //bound on the next level of w

       OutEdgeIt e;

       for(G.first(e,w); G.valid(e); G.next(e)) {

 	if ( (*flow)[e] == (*capacity)[e] ) continue; 

 	Node v=G.head(e);            

 	if( lev > level[v] ) { //Push is allowed now

 	  if ( excess[v]==0 && v!=t && v!=s ) {

 	    int lev_v=level[v];

 	    active[lev_v].push(v);

 	  }

 	  T cap=(*capacity)[e];

 	  T flo=(*flow)[e];

 	  T remcap=cap-flo;

 	  if ( remcap >= exc ) { //A nonsaturating push.

 	    flow->set(e, flo+exc);

 	    excess.set(v, excess[v]+exc);

 	    exc=0;

 	    break; 

 	  } else { //A saturating push.

 	    flow->set(e, cap);

 	    excess.set(v, excess[v]+remcap);

 	    exc-=remcap;

 	  }

 	} else if ( newlevel > level[v] ) newlevel = level[v];

       } //for out edges wv 

       if ( exc > 0 ) {	

 	InEdgeIt e;

 	for(G.first(e,w); G.valid(e); G.next(e)) {

 	  if( (*flow)[e] == 0 ) continue; 

 	  Node v=G.tail(e); 

 	  if( lev > level[v] ) { //Push is allowed now

 	    if ( excess[v]==0 && v!=t && v!=s ) {

 	      int lev_v=level[v];

 	      active[lev_v].push(v);

 	    }

 	    T flo=(*flow)[e];

 	    if ( flo >= exc ) { //A nonsaturating push.

 	      flow->set(e, flo-exc);

 	      excess.set(v, excess[v]+exc);

 	      exc=0;

 	      break; 

 	    } else {  //A saturating push.

 	      excess.set(v, excess[v]+flo);

 	      exc-=flo;

 	      flow->set(e,0);

 	    }  

 	  } else if ( newlevel > level[v] ) newlevel = level[v];

 	} //for in edges vw

       } // if w still has excess after the out edge for cycle

       excess.set(w, exc);

       return newlevel;

      }

     void preflowPreproc ( flowEnum fe, VecStack& active, 

 			  VecNode& level_list, NNMap& left, NNMap& right ) {

       std::queue<Node> bfs_queue;

       switch ( fe ) {

       case ZERO_FLOW: 

 	{

 	  //Reverse_bfs from t, to find the starting level.

 	  level.set(t,0);

 	  bfs_queue.push(t);

 	  while (!bfs_queue.empty()) {

 	    Node v=bfs_queue.front();	

 	    bfs_queue.pop();

 	    int l=level[v]+1;

 	    InEdgeIt e;

 	    for(G.first(e,v); G.valid(e); G.next(e)) {

 	      Node w=G.tail(e);

 	      if ( level[w] == n && w != s ) {

 		bfs_queue.push(w);

 		Node first=level_list[l];

 		if ( G.valid(first) ) left.set(first,w);

 		right.set(w,first);

 		level_list[l]=w;

 		level.set(w, l);

 	      }

 	    }

 	  }

 	  //the starting flow

 	  OutEdgeIt e;

 	  for(G.first(e,s); G.valid(e); G.next(e)) 

 	    {

 	      T c=(*capacity)[e];

 	      if ( c == 0 ) continue;

 	      Node w=G.head(e);

 	      if ( level[w] < n ) {	  

 		if ( excess[w] == 0 && w!=t ) active[level[w]].push(w);

 		flow->set(e, c); 

 		excess.set(w, excess[w]+c);

 	      }

 	    }

 	  break;

 	}

       case GEN_FLOW:

       case PREFLOW:

 	{

 	  //Reverse_bfs from t in the residual graph, 

 	  //to find the starting level.

 	  level.set(t,0);

 	  bfs_queue.push(t);

 	  while (!bfs_queue.empty()) {

 	    Node v=bfs_queue.front();	

 	    bfs_queue.pop();

 	    int l=level[v]+1;

 	    InEdgeIt e;

 	    for(G.first(e,v); G.valid(e); G.next(e)) {

 	      if ( (*capacity)[e] == (*flow)[e] ) continue;

 	      Node w=G.tail(e);

 	      if ( level[w] == n && w != s ) {

 		bfs_queue.push(w);

 		Node first=level_list[l];

 		if ( G.valid(first) ) left.set(first,w);

 		right.set(w,first);

 		level_list[l]=w;

 		level.set(w, l);

 	      }

 	    }

 	    OutEdgeIt f;

 	    for(G.first(f,v); G.valid(f); G.next(f)) {

 	      if ( 0 == (*flow)[f] ) continue;

 	      Node w=G.head(f);

 	      if ( level[w] == n && w != s ) {

 		bfs_queue.push(w);

 		Node first=level_list[l];

 		if ( G.valid(first) ) left.set(first,w);

 		right.set(w,first);

 		level_list[l]=w;

 		level.set(w, l);

 	      }

 	    }

 	  }

 	  //the starting flow

 	  OutEdgeIt e;

 	  for(G.first(e,s); G.valid(e); G.next(e)) 

 	    {

 	      T rem=(*capacity)[e]-(*flow)[e];

 	      if ( rem == 0 ) continue;

 	      Node w=G.head(e);

 	      if ( level[w] < n ) {	  

 		if ( excess[w] == 0 && w!=t ) active[level[w]].push(w);

 		flow->set(e, (*capacity)[e]); 

 		excess.set(w, excess[w]+rem);

 	      }

 	    }

 	  InEdgeIt f;

 	  for(G.first(f,s); G.valid(f); G.next(f)) 

 	    {

 	      if ( (*flow)[f] == 0 ) continue;

 	      Node w=G.tail(f);

 	      if ( level[w] < n ) {	  

 		if ( excess[w] == 0 && w!=t ) active[level[w]].push(w);

 		excess.set(w, excess[w]+(*flow)[f]);

 		flow->set(f, 0); 

 	      }

 	    }  

 	  break;

 	} //case PREFLOW

       }

     } //preflowPreproc

     void relabel( const Node w, int newlevel, VecStack& active,  

 		  VecNode& level_list, NNMap& left, 

 		  NNMap& right, int& b, int& k, const bool what_heur ) {

       T lev=level[w];	

       Node right_n=right[w];

       Node left_n=left[w];

       //unlacing starts

       if ( G.valid(right_n) ) {

 	if ( G.valid(left_n) ) {

 	  right.set(left_n, right_n);

 	  left.set(right_n, left_n);

 	} else {

 	  level_list[lev]=right_n;   

 	  left.set(right_n, INVALID);

 	} 

       } else {

 	if ( G.valid(left_n) ) {

 	  right.set(left_n, INVALID);

 	} else { 

 	  level_list[lev]=INVALID;   

 	} 

       } 

       //unlacing ends

       if ( !G.valid(level_list[lev]) ) {

 	//gapping starts

 	for (int i=lev; i!=k ; ) {

 	  Node v=level_list[++i];

 	  while ( G.valid(v) ) {

 	    level.set(v,n);

 	    v=right[v];

 	  }

 	  level_list[i]=INVALID;

 	  if ( !what_heur ) {

 	    while ( !active[i].empty() ) {

 	      active[i].pop();    //FIXME: ezt szebben kene

 	    }

 	  }	     

 	}

 	level.set(w,n);

 	b=lev-1;

 	k=b;

 	//gapping ends

       } else {

 	if ( newlevel == n ) level.set(w,n); 

 	else {

 	  level.set(w,++newlevel);

 	  active[newlevel].push(w);

 	  if ( what_heur ) b=newlevel;

 	  if ( k < newlevel ) ++k;      //now k=newlevel

 	  Node first=level_list[newlevel];

 	  if ( G.valid(first) ) left.set(first,w);

 	  right.set(w,first);

 	  left.set(w,INVALID);

 	  level_list[newlevel]=w;

 	}

       }

     } //relabel

 #endif //PREFLOW_H

 #endif //HUGO_PREFLOW_H