src/work/jacint/preflow_res.h
author athos
Wed, 23 Mar 2005 11:51:40 +0000
changeset 1247 60708e1475ae
parent 921 818510fa3d99
permissions -rw-r--r--
Completions.
     1 // -*- C++ -*-
     2 //The same as preflow.h, using ResGraphWrapper
     3 #ifndef LEMON_PREFLOW_RES_H
     4 #define LEMON_PREFLOW_RES_H
     5 
     6 #define H0 20
     7 #define H1 1
     8 
     9 #include <vector>
    10 #include <queue>
    11 #include <graph_wrapper.h>
    12 
    13 #include<iostream>
    14 
    15 namespace lemon {
    16 
    17   template <typename Graph, typename T, 
    18 	    typename CapMap=typename Graph::template EdgeMap<T>, 
    19             typename FlowMap=typename Graph::template EdgeMap<T> >
    20   class PreflowRes {
    21     
    22     typedef typename Graph::Node Node;
    23     typedef typename Graph::Edge Edge;
    24     typedef typename Graph::NodeIt NodeIt;
    25     typedef typename Graph::OutEdgeIt OutEdgeIt;
    26     typedef typename Graph::InEdgeIt InEdgeIt;
    27     
    28     const Graph& G;
    29     Node s;
    30     Node t;
    31     const CapMap& capacity;  
    32     FlowMap& flow;
    33     T value;
    34     bool constzero;
    35 
    36     typedef ResGraphWrapper<const Graph, T, CapMap, FlowMap> ResGW;
    37     typedef typename ResGW::OutEdgeIt ResOutEdgeIt;
    38     typedef typename ResGW::InEdgeIt ResInEdgeIt;
    39     typedef typename ResGW::Edge ResEdge;
    40  
    41   public:
    42     PreflowRes(Graph& _G, Node _s, Node _t, CapMap& _capacity, 
    43 	    FlowMap& _flow, bool _constzero ) :
    44       G(_G), s(_s), t(_t), capacity(_capacity), flow(_flow), constzero(_constzero) {}
    45     
    46     
    47     void run() {
    48 
    49       ResGW res_graph(G, capacity, flow);
    50 
    51       value=0;                //for the subsequent runs
    52 
    53       bool phase=0;        //phase 0 is the 1st phase, phase 1 is the 2nd
    54       int n=G.nodeNum(); 
    55       int heur0=(int)(H0*n);  //time while running 'bound decrease' 
    56       int heur1=(int)(H1*n);  //time while running 'highest label'
    57       int heur=heur1;         //starting time interval (#of relabels)
    58       bool what_heur=1;       
    59       /*
    60 	what_heur is 0 in case 'bound decrease' 
    61 	and 1 in case 'highest label'
    62       */
    63       bool end=false;     
    64       /*
    65 	Needed for 'bound decrease', 'true'
    66 	means no active nodes are above bound b.
    67       */
    68       int relabel=0;
    69       int k=n-2;  //bound on the highest level under n containing a node
    70       int b=k;    //bound on the highest level under n of an active node
    71       
    72       typename Graph::template NodeMap<int> level(G,n);      
    73       typename Graph::template NodeMap<T> excess(G); 
    74 
    75       std::vector<Node> active(n-1,INVALID);
    76       typename Graph::template NodeMap<Node> next(G,INVALID);
    77       //Stack of the active nodes in level i < n.
    78       //We use it in both phases.
    79 
    80       typename Graph::template NodeMap<Node> left(G,INVALID);
    81       typename Graph::template NodeMap<Node> right(G,INVALID);
    82       std::vector<Node> level_list(n,INVALID);
    83       /*
    84 	List of the nodes in level i<n.
    85       */
    86 
    87 
    88       /*
    89 	Reverse_bfs from t in the residual graph, 
    90 	to find the starting level.
    91       */
    92       level.set(t,0);
    93       std::queue<Node> bfs_queue;
    94       bfs_queue.push(t);
    95       
    96       while (!bfs_queue.empty()) {
    97 	
    98 	Node v=bfs_queue.front();	
    99 	bfs_queue.pop();
   100 	int l=level[v]+1;
   101 	
   102 	ResInEdgeIt e;
   103 	for(res_graph.first(e,v); res_graph.valid(e); 
   104 	    res_graph.next(e)) {
   105 	  Node w=res_graph.source(e);
   106 	  if ( level[w] == n && w != s ) {
   107 	    bfs_queue.push(w);
   108 	    Node first=level_list[l];
   109 	    if ( G.valid(first) ) left.set(first,w);
   110 	    right.set(w,first);
   111 	    level_list[l]=w;
   112 	    level.set(w, l);
   113 	  }
   114 	}
   115       }
   116       
   117 	
   118       if ( !constzero ) {
   119 	/*
   120 	  Counting the excess
   121 	*/
   122 	NodeIt v;
   123 	for(G.first(v); G.valid(v); G.next(v)) {
   124 	  T exc=0;
   125 
   126 	  InEdgeIt e;
   127 	  for(G.first(e,v); G.valid(e); G.next(e)) exc+=flow[e];
   128 	  OutEdgeIt f;
   129 	  for(G.first(f,v); G.valid(f); G.next(f)) exc-=flow[f];
   130 
   131 	  excess.set(v,exc);	  
   132 
   133 	  //putting the active nodes into the stack
   134 	  int lev=level[v];
   135 	  if ( exc > 0 && lev < n ) {
   136 	    next.set(v,active[lev]);
   137 	    active[lev]=v;
   138 	  }
   139 	}
   140       }
   141      
   142 
   143 
   144       //the starting flow
   145       ResOutEdgeIt e;
   146       for(res_graph.first(e,s); res_graph.valid(e); 
   147 	  res_graph.next(e)) {
   148 	  Node w=res_graph.target(e);
   149 	  if ( level[w] < n ) {	  
   150 	    if ( excess[w] == 0 && w!=t ) {
   151 	      next.set(w,active[level[w]]);
   152 	      active[level[w]]=w;
   153 	    }
   154 	    T rem=res_graph.resCap(e);
   155 	    excess.set(w, excess[w]+rem);
   156 	    res_graph.augment(e, rem ); 
   157 	  }
   158       }
   159 	
   160 
   161       /* 
   162 	 End of preprocessing 
   163       */
   164 
   165 
   166 
   167       /*
   168 	Push/relabel on the highest level active nodes.
   169       */	
   170       while ( true ) {
   171 	
   172 	if ( b == 0 ) {
   173 	  if ( phase ) break;
   174 	  
   175 	  if ( !what_heur && !end && k > 0 ) {
   176 	    b=k;
   177 	    end=true;
   178 	  } else {
   179 	    phase=1;
   180 	    level.set(s,0);
   181 	    std::queue<Node> bfs_queue;
   182 	    bfs_queue.push(s);
   183 	    
   184 	    while (!bfs_queue.empty()) {
   185 	      
   186 	      Node v=bfs_queue.front();	
   187 	      bfs_queue.pop();
   188 	      int l=level[v]+1;
   189 	      
   190 	      ResInEdgeIt e;
   191 	      for(res_graph.first(e,v); 
   192 		  res_graph.valid(e); res_graph.next(e)) {
   193 		Node u=res_graph.source(e);
   194 		if ( level[u] >= n ) { 
   195 		  bfs_queue.push(u);
   196 		  level.set(u, l);
   197 		  if ( excess[u] > 0 ) {
   198 		    next.set(u,active[l]);
   199 		    active[l]=u;
   200 		  }
   201 		}
   202 	      }
   203 	    
   204 	    }
   205 	    b=n-2;
   206 	  }
   207 	    
   208 	}
   209 	  
   210 	  
   211 	if ( !G.valid(active[b]) ) --b; 
   212 	else {
   213 	  end=false;  
   214 
   215 	  Node w=active[b];
   216 	  active[b]=next[w];
   217 	  int lev=level[w];
   218 	  T exc=excess[w];
   219 	  int newlevel=n;       //bound on the next level of w
   220 	  
   221 	  ResOutEdgeIt e;
   222 	  for(res_graph.first(e,w); res_graph.valid(e); res_graph.next(e)) {
   223 	    
   224 	    Node v=res_graph.target(e);            
   225 	    if( lev > level[v] ) {      
   226 	      /*Push is allowed now*/
   227 	      
   228 	      if ( excess[v]==0 && v!=t && v!=s ) {
   229 		int lev_v=level[v];
   230 		next.set(v,active[lev_v]);
   231 		active[lev_v]=v;
   232 	      }
   233 	      
   234 	      T remcap=res_graph.resCap(e);
   235 	      
   236 	      if ( remcap >= exc ) {       
   237 		/*A nonsaturating push.*/
   238 		res_graph.augment(e, exc);
   239 		excess.set(v, excess[v]+exc);
   240 		exc=0;
   241 		break; 
   242 		
   243 	      } else { 
   244 		/*A saturating push.*/
   245 		
   246 		res_graph.augment(e, remcap);
   247 		excess.set(v, excess[v]+remcap);
   248 		exc-=remcap;
   249 	      }
   250 	    } else if ( newlevel > level[v] ){
   251 	      newlevel = level[v];
   252 	    }	    
   253 	    
   254 	  }
   255 
   256 	excess.set(w, exc);
   257 	 
   258 	/*
   259 	  Relabel
   260 	*/
   261 	
   262 
   263 	if ( exc > 0 ) {
   264 	  //now 'lev' is the old level of w
   265 	
   266 	  if ( phase ) {
   267 	    level.set(w,++newlevel);
   268 	    next.set(w,active[newlevel]);
   269 	    active[newlevel]=w;
   270 	    b=newlevel;
   271 	  } else {
   272 	    //unlacing starts
   273 	    Node right_n=right[w];
   274 	    Node left_n=left[w];
   275 
   276 	    if ( G.valid(right_n) ) {
   277 	      if ( G.valid(left_n) ) {
   278 		right.set(left_n, right_n);
   279 		left.set(right_n, left_n);
   280 	      } else {
   281 		level_list[lev]=right_n;   
   282 		left.set(right_n, INVALID);
   283 	      } 
   284 	    } else {
   285 	      if ( G.valid(left_n) ) {
   286 		right.set(left_n, INVALID);
   287 	      } else { 
   288 		level_list[lev]=INVALID;   
   289 	      } 
   290 	    } 
   291 	    //unlacing ends
   292 		
   293 	    if ( !G.valid(level_list[lev]) ) {
   294 	      
   295 	       //gapping starts
   296 	      for (int i=lev; i!=k ; ) {
   297 		Node v=level_list[++i];
   298 		while ( G.valid(v) ) {
   299 		  level.set(v,n);
   300 		  v=right[v];
   301 		}
   302 		level_list[i]=INVALID;
   303 		if ( !what_heur ) active[i]=INVALID;
   304 	      }	     
   305 
   306 	      level.set(w,n);
   307 	      b=lev-1;
   308 	      k=b;
   309 	      //gapping ends
   310 	    
   311 	    } else {
   312 	      
   313 	      if ( newlevel == n ) level.set(w,n); 
   314 	      else {
   315 		level.set(w,++newlevel);
   316 		next.set(w,active[newlevel]);
   317 		active[newlevel]=w;
   318 		if ( what_heur ) b=newlevel;
   319 		if ( k < newlevel ) ++k;      //now k=newlevel
   320 		Node first=level_list[newlevel];
   321 		if ( G.valid(first) ) left.set(first,w);
   322 		right.set(w,first);
   323 		left.set(w,INVALID);
   324 		level_list[newlevel]=w;
   325 	      }
   326 	    }
   327 
   328 
   329 	    ++relabel; 
   330 	    if ( relabel >= heur ) {
   331 	      relabel=0;
   332 	      if ( what_heur ) {
   333 		what_heur=0;
   334 		heur=heur0;
   335 		end=false;
   336 	      } else {
   337 		what_heur=1;
   338 		heur=heur1;
   339 		b=k; 
   340 	      }
   341 	    }
   342 	  } //phase 0
   343 	  
   344 	  
   345 	} // if ( exc > 0 )
   346 	  
   347 	
   348 	}  // if stack[b] is nonempty
   349 	
   350       } // while(true)
   351 
   352 
   353       value = excess[t];
   354       /*Max flow value.*/
   355      
   356     } //void run()
   357 
   358 
   359 
   360 
   361 
   362     /*
   363       Returns the maximum value of a flow.
   364      */
   365 
   366     T flowValue() {
   367       return value;
   368     }
   369 
   370 
   371     FlowMap Flow() {
   372       return flow;
   373       }
   374 
   375 
   376     
   377     void Flow(FlowMap& _flow ) {
   378       NodeIt v;
   379       for(G.first(v) ; G.valid(v); G.next(v))
   380 	_flow.set(v,flow[v]);
   381     }
   382 
   383 
   384 
   385     /*
   386       Returns the minimum min cut, by a bfs from s in the residual graph.
   387     */
   388    
   389     template<typename _CutMap>
   390     void minMinCut(_CutMap& M) {
   391     
   392       std::queue<Node> queue;
   393       
   394       M.set(s,true);      
   395       queue.push(s);
   396 
   397       while (!queue.empty()) {
   398         Node w=queue.front();
   399 	queue.pop();
   400 
   401 	OutEdgeIt e;
   402 	for(G.first(e,w) ; G.valid(e); G.next(e)) {
   403 	  Node v=G.target(e);
   404 	  if (!M[v] && flow[e] < capacity[e] ) {
   405 	    queue.push(v);
   406 	    M.set(v, true);
   407 	  }
   408 	} 
   409 
   410 	InEdgeIt f;
   411 	for(G.first(f,w) ; G.valid(f); G.next(f)) {
   412 	  Node v=G.source(f);
   413 	  if (!M[v] && flow[f] > 0 ) {
   414 	    queue.push(v);
   415 	    M.set(v, true);
   416 	  }
   417 	} 
   418       }
   419     }
   420 
   421 
   422   
   423     /*
   424       Returns the maximum min cut, by a reverse bfs 
   425       from t in the residual graph.
   426     */
   427     
   428     template<typename _CutMap>
   429     void maxMinCut(_CutMap& M) {
   430     
   431       std::queue<Node> queue;
   432       
   433       M.set(t,true);        
   434       queue.push(t);
   435 
   436       while (!queue.empty()) {
   437         Node w=queue.front();
   438 	queue.pop();
   439 
   440 
   441 	InEdgeIt e;
   442 	for(G.first(e,w) ; G.valid(e); G.next(e)) {
   443 	  Node v=G.source(e);
   444 	  if (!M[v] && flow[e] < capacity[e] ) {
   445 	    queue.push(v);
   446 	    M.set(v, true);
   447 	  }
   448 	}
   449 	
   450 	OutEdgeIt f;
   451 	for(G.first(f,w) ; G.valid(f); G.next(f)) {
   452 	  Node v=G.target(f);
   453 	  if (!M[v] && flow[f] > 0 ) {
   454 	    queue.push(v);
   455 	    M.set(v, true);
   456 	  }
   457 	}
   458       }
   459 
   460       NodeIt v;
   461       for(G.first(v) ; G.valid(v); G.next(v)) {
   462 	M.set(v, !M[v]);
   463       }
   464 
   465     }
   466 
   467 
   468 
   469     template<typename CutMap>
   470     void minCut(CutMap& M) {
   471       minMinCut(M);
   472     }
   473 
   474     
   475     
   476     void resetTarget (Node _t) {t=_t;}
   477     void resetSource (Node _s) {s=_s;}
   478    
   479     void resetCap (CapMap _cap) {capacity=_cap;}
   480 
   481     void resetFlow (FlowMap _flow, bool _constzero) {
   482       flow=_flow;
   483       constzero=_constzero;
   484     }
   485 
   486 
   487   };
   488 
   489 } //namespace lemon
   490 
   491 #endif //LEMON_PREFLOW_RES_H
   492 
   493 
   494 
   495