Changeset 97:a5127ecb2914 in lemon-0.x for src/work/jacint/preflow_push_max_flow.h

Timestamp:

02/18/04 15:42:38 (20 years ago)

Author:

jacint

Branch:

default

Phase:

public

Convert:

svn:c9d7d8f5-90d6-0310-b91f-818b3a526b0e/lemon/trunk@126

Message:

javitott valtozat

File:

• src/work/jacint/preflow_push_max_flow.h (modified) (8 diffs)

src/work/jacint/preflow_push_max_flow.h

@@ +1 @@
+// -*- C++ -*-
 /*
 preflow_push_max_flow_h
@@ -16 +17 @@
 T maxflow() : returns the value of a maximum flow
 
-NodeMap<bool> mincut(): returns a 
-     characteristic vector of a minimum cut.
+void mincut(CutMap& M) : sets M to the characteristic vector of a 
+     minimum cut. M should be a map of bools initialized to false.
+
 */
 
 #ifndef PREFLOW_PUSH_MAX_FLOW_H
 #define PREFLOW_PUSH_MAX_FLOW_H
+
+#define A 1
 
 #include <algorithm>
@@ -32 +36 @@
 namespace marci {
 
-  template <typename Graph, typename T>
+  template <typename Graph, typename T,  
+    typename FlowMap=typename Graph::EdgeMap<T>, typename CapMap=typename Graph::EdgeMap<T>, 
+    typename IntMap=typename Graph::NodeMap<int>, typename TMap=typename Graph::NodeMap<T> >
   class preflow_push_max_flow {
     
@@ -43 +49 @@
     NodeIt s;
     NodeIt t;
-    typename Graph::EdgeMap<T>& capacity; 
-    T value;
-    typename Graph::NodeMap<bool> mincutvector;    
-
-
-     
+    IntMap level;
+    CapMap& capacity;  
+    int empty_level;    //an empty level in the end of run()
+    T value; 
+    
   public:
-        
-    preflow_push_max_flow ( Graph& _G, NodeIt _s, NodeIt _t, 
-                            typename Graph::EdgeMap<T>& _capacity) : 
-      G(_G), s(_s), t(_t), capacity(_capacity), mincutvector(_G, false) { }
+      
+    preflow_push_max_flow(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity) :
+      G(_G), s(_s), t(_t), level(_G), capacity(_capacity) { }
 
 
@@ -63 +67 @@
     void run() {
  
-      typename Graph::EdgeMap<T> flow(G, 0); 
-      typename Graph::NodeMap<int> level(G);   
-      typename Graph::NodeMap<T> excess(G);    
-            
-      int n=G.nodeNum();                       
+      int n=G.nodeNum(); 
       int b=n-2; 
       /*
-        b is a bound on the highest level of an active Node. 
-        In the beginning it is at most n-2.
-      */
-      
-      std::vector<int> numb(n);     //The number of Nodes on level i < n.
-      std::vector<std::stack<NodeIt> > stack(2*n-1);    
-      //Stack of the active Nodes in level i.
+        b is a bound on the highest level of an active node. 
+      */
+
+      IntMap level(G,n);      
+      TMap excess(G); 
+      FlowMap flow(G,0);
+
+      std::vector<int> numb(n);    
+      /*
+        The number of nodes on level i < n. It is
+        initialized to n+1, because of the reverse_bfs-part.
+      */
+
+      std::vector<std::stack<NodeIt> > stack(n);    
+      //Stack of the active nodes in level i.
+
 
       /*Reverse_bfs from t, to find the starting level.*/
-      reverse_bfs<Graph> bfs(G, t);
-      bfs.run();
-      for(EachNodeIt v=G.template first<EachNodeIt>(); v.valid(); ++v) 
-        {
-          int dist=bfs.dist(v);
-          level.set(v, dist); 
-          ++numb[dist];
+      level.set(t,0);
+      std::queue<NodeIt> bfs_queue;
+      bfs_queue.push(t);
+
+      while (!bfs_queue.empty()) {
+
+        NodeIt v=bfs_queue.front();     
+        bfs_queue.pop();
+        int l=level.get(v)+1;
+
+        for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
+          NodeIt w=G.tail(e);
+          if ( level.get(w) == n ) {
+            bfs_queue.push(w);
+            ++numb[l];
+            level.set(w, l);
+          }
         }
-
+      }
+        
       level.set(s,n);
 
-      /* Starting flow. It is everywhere 0 at the moment. */
+
+
+      /* Starting flow. It is everywhere 0 at the moment. */     
       for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e) 
         {
-          if ( capacity.get(e) > 0 ) {
-            NodeIt w=G.head(e);
+          if ( capacity.get(e) == 0 ) continue;
+          NodeIt w=G.head(e);
+          if ( level.get(w) < n ) {       
+            if ( excess.get(w) == 0 && w!=t ) stack[level.get(w)].push(w); 
             flow.set(e, capacity.get(e)); 
-            stack[level.get(w)].push(w); 
             excess.set(w, excess.get(w)+capacity.get(e));
           }
         }
-
+      
       /* 
          End of preprocessing 
@@ -106 +129 @@
 
 
-
       /*
-        Push/relabel on the highest level active Nodes.
-      */
-        
-      /*While there exists an active Node.*/
+        Push/relabel on the highest level active nodes.
+      */
+      /*While there exists an active node.*/
       while (b) { 
-
-        /*We decrease the bound if there is no active node of level b.*/
-        if (stack[b].empty()) {
+        if ( stack[b].empty() ) { 
           --b;
-        } else {
-
-          NodeIt w=stack[b].top();    //w is the highest label active Node.
-          stack[b].pop();                    //We delete w from the stack.
-        
-          int newlevel=2*n-2;                //In newlevel we maintain the next level of w.
-        
+          continue;
+        } 
+        
+        NodeIt w=stack[b].top();        //w is a highest label active node.
+        stack[b].pop();           
+        int lev=level.get(w);
+        int exc=excess.get(w);
+        int newlevel=2*n-2;      //In newlevel we bound the next level of w.
+        
+        //  if ( level.get(w) < n ) { //Nem tudom ez mukodik-e
           for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
-            NodeIt v=G.head(e);
-            /*e is the Edge wv.*/
-
-            if (flow.get(e)<capacity.get(e)) {              
-              /*e is an Edge of the residual graph */
-
-              if(level.get(w)==level.get(v)+1) {      
-                /*Push is allowed now*/
-
-                if (capacity.get(e)-flow.get(e) > excess.get(w)) {       
-                  /*A nonsaturating push.*/
-                  
-                  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 
-                  /*v becomes active.*/
-                  
-                  flow.set(e, flow.get(e)+excess.get(w));
-                  excess.set(v, excess.get(v)+excess.get(w));
-                  excess.set(w,0);
-                  //std::cout << w << " " << v <<" elore elen nonsat pump "  << std::endl;
-                  break; 
-                } else { 
-                  /*A saturating push.*/
-
-                  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 
-                  /*v becomes active.*/
-
-                  excess.set(v, excess.get(v)+capacity.get(e)-flow.get(e));
-                  excess.set(w, excess.get(w)-capacity.get(e)+flow.get(e));
-                  flow.set(e, capacity.get(e));
-                  //std::cout << w <<" " << v <<" elore elen sat pump "   << std::endl;
-                  if (excess.get(w)==0) break; 
-                  /*If w is not active any more, then we go on to the next Node.*/
-                  
-                } // if (capacity.get(e)-flow.get(e) > excess.get(w))
-              } // if (level.get(w)==level.get(v)+1)
-            
-              else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}
-            
-            } //if (flow.get(e)<capacity.get(e))
-         
-          } //for(OutEdgeIt e=G.first_OutEdge(w); e.valid(); ++e) 
+            
+            if ( flow.get(e) == capacity.get(e) ) continue; 
+            NodeIt v=G.head(e);            
+            //e=wv          
+            
+            if( lev > level.get(v) ) {      
+              /*Push is allowed now*/
+              
+              if ( excess.get(v)==0 && v != s && v !=t ) 
+                stack[level.get(v)].push(v); 
+              /*v becomes active.*/
+              
+              int cap=capacity.get(e);
+              int flo=flow.get(e);
+              int remcap=cap-flo;
+              
+              if ( remcap >= exc ) {       
+                /*A nonsaturating push.*/
+                
+                flow.set(e, flo+exc);
+                excess.set(v, excess.get(v)+exc);
+                exc=0;
+                break; 
+                
+              } else { 
+                /*A saturating push.*/
+                
+                flow.set(e, cap );
+                excess.set(v, excess.get(v)+remcap);
+                exc-=remcap;
+              }
+            } else if ( newlevel > level.get(v) ) newlevel = level.get(v);
+            
+          } //for out edges wv 
+        
+        
+        if ( exc > 0 ) {        
+          for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
+            
+            if( flow.get(e) == 0 ) continue; 
+            NodeIt v=G.tail(e);  
+            //e=vw
+            
+            if( lev > level.get(v) ) {  
+              /*Push is allowed now*/
+              
+              if ( excess.get(v)==0 && v != s && v !=t) 
+                stack[level.get(v)].push(v); 
+              /*v becomes active.*/
+              
+              int flo=flow.get(e);
+              
+              if ( flo >= exc ) { 
+                /*A nonsaturating push.*/
+                
+                flow.set(e, flo-exc);
+                excess.set(v, excess.get(v)+exc);
+                exc=0;
+                break; 
+              } else {                                               
+                /*A saturating push.*/
+                
+                excess.set(v, excess.get(v)+flo);
+                exc-=flo;
+                flow.set(e,0);
+              }  
+            } else if ( newlevel > level.get(v) ) newlevel = level.get(v);
+            
+          } //for in edges vw
           
-
-
-          for(InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
-            NodeIt v=G.tail(e);
-            /*e is the Edge vw.*/
-
-            if (excess.get(w)==0) break;
-            /*It may happen, that w became inactive in the first 'for' cycle.*/         
-  
-            if(flow.get(e)>0) {             
-              /*e is an Edge of the residual graph */
-
-              if(level.get(w)==level.get(v)+1) {  
-                /*Push is allowed now*/
-                
-                if (flow.get(e) > excess.get(w)) { 
-                  /*A nonsaturating push.*/
-                  
-                  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 
-                  /*v becomes active.*/
-
-                  flow.set(e, flow.get(e)-excess.get(w));
-                  excess.set(v, excess.get(v)+excess.get(w));
-                  excess.set(w,0);
-                  //std::cout << v << " " << w << " vissza elen nonsat pump "     << std::endl;
-                  break; 
-                } else {                                               
-                  /*A saturating push.*/
-                  
-                  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 
-                  /*v becomes active.*/
-                  
-                  flow.set(e,0);
-                  excess.set(v, excess.get(v)+flow.get(e));
-                  excess.set(w, excess.get(w)-flow.get(e));
-                  //std::cout << v <<" " << w << " vissza elen sat pump "     << std::endl;
-                  if (excess.get(w)==0) { break;}
-                } //if (flow.get(e) > excess.get(v)) 
-              } //if(level.get(w)==level.get(v)+1)
-              
-              else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}
-              //std::cout << "Leveldecrease of Node " << w << " to " << newlevel << std::endl; 
-
-            } //if (flow.get(e)>0)
-
-          } //for in-Edge
-
-
-
-
-          /*
-            Relabel
-          */
-          if (excess.get(w)>0) {
-            /*Now newlevel <= n*/
-
-            int l=level.get(w);         //l is the old level of w.
-            --numb[l];
-           
-            if (newlevel == n) {
-              level.set(w,n);
-              
-            } else {
-              
-              if (numb[l]) {
-                /*If the level of w remains nonempty.*/
-                
-                level.set(w,++newlevel);
-                ++numb[newlevel];
-                stack[newlevel].push(w);
-                b=newlevel;
-              } else { 
-                /*If the level of w gets empty.*/
-              
-                for (EachNodeIt v=G.template first<EachNodeIt>(); v.valid() ; ++v) {
-                  if (level.get(v) >= l ) { 
-                    level.set(v,n);  
-                  }
-                }
-                
-                for (int i=l+1 ; i!=n ; ++i) numb[i]=0; 
-              } //if (numb[l])
-        
-            } // if (newlevel = n)
-         
-          } // if (excess.get(w)>0)
-
-
-        } //else
-       
+        } // 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
+          level.set(w,++newlevel);
+          --numb[lev];
+            
+          if ( !numb[lev] && lev < A*n ) {  //If the level of w gets empty. 
+              
+            for (EachNodeIt v=G.template first<EachNodeIt>(); v.valid() ; ++v) {
+              if (level.get(v) > lev ) level.set(v,n);  
+            }
+            for (int i=lev+1 ; i!=n ; ++i) numb[i]=0; 
+            if ( newlevel < n ) newlevel=n; 
+          } else if ( newlevel < n ) {
+            ++numb[newlevel]; 
+            stack[newlevel].push(w);
+            b=newlevel;
+          }
+        }
+
+
+
       } //while(b)
 
@@ -263 +253 @@
       
 
-
-      /*
-        We find an empty level, e. The Nodes above this level give 
-        a minimum cut.
-      */
-      
-      int e=1;
-      
-      while(e) {
-        if(numb[e]) ++e;
+      /* 
+         We count empty_level. The nodes above this level is a mincut.
+      */
+      while(true) {
+        if(numb[empty_level]) ++empty_level;
         else break;
       } 
-      for (EachNodeIt v=G.template first<EachNodeIt>(); v.valid(); ++v) {
-        if (level.get(v) > e) mincutvector.set(v, true);
-      }
-      
-
+      
     } // void run()
 
@@ -296 +277 @@
     /*
       Returns a minimum cut.
-    */
-    
-    typename Graph::NodeMap<bool> mincut() {
-      return mincutvector;
+    */    
+    template<typename CutMap>
+    void mincut(CutMap& M) {
+
+      for (EachNodeIt v=G.template first<EachNodeIt>(); v.valid(); ++v) {
+        if ( level.get(v) > empty_level ) M.set(v, true);
+      }
     }
-    
+
 
   };