Changeset 97:a5127ecb2914 in lemon-0.x for src/work/jacint/preflow_push_hl.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_hl.h (modified) (10 diffs)

src/work/jacint/preflow_push_hl.h

@@ -4 +4 @@
 by jacint. 
 Runs the highest label variant of the preflow push algorithm with 
-running time O(n^2\sqrt(m)). 
+running time O(n^2\sqrt(m)), and with the 'empty level' heuristic. 
+
+'A' is a parameter for the empty_level heuristic
 
 Member functions:
@@ -16 +18 @@
 T flowonedge(EdgeIt e) : for a fixed maximum flow x it returns x(e) 
 
-Graph::EdgeMap<T> allflow() : returns the fixed maximum flow x
-
-Graph::NodeMap<bool> mincut() : returns a 
-     characteristic vector of a minimum cut. (An empty level 
-     in the algorithm gives a minimum cut.)
+FlowMap allflow() : returns the fixed maximum flow x
+
+void mincut(CutMap& M) : sets M to the characteristic vector of a 
+     minimum cut. M should be a map of bools initialized to false.
+
+void min_mincut(CutMap& M) : sets M to the characteristic vector of the 
+     minimum min cut. M should be a map of bools initialized to false.
+
+void max_mincut(CutMap& M) : sets M to the characteristic vector of the 
+     maximum min cut. M should be a map of bools initialized to false.
+
 */
 
@@ -30 +38 @@
 #include <vector>
 #include <stack>
-
-#include <reverse_bfs.h>
+#include <queue>
 
 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_hl {
     
@@ -47 +56 @@
     NodeIt s;
     NodeIt t;
-    typename Graph::EdgeMap<T> flow;
-    typename Graph::EdgeMap<T> capacity; 
+    FlowMap flow;
+    CapMap& capacity;  
     T value;
-    typename Graph::NodeMap<bool> mincutvector;
-
+    
   public:
 
-    preflow_push_hl(Graph& _G, NodeIt _s, NodeIt _t, 
-                    typename Graph::EdgeMap<T>& _capacity) :
-      G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity), 
-      mincutvector(_G, true) { }
-
-
-    /*
-      The run() function runs the highest label preflow-push, 
-      running time: O(n^2\sqrt(m))
-    */
+    preflow_push_hl(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity) :
+      G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity) { }
+
+
+    
+
     void run() {
  
-      std::cout<<"A is "<<A<<" ";
-
-      typename Graph::NodeMap<int> level(G);      
-      typename Graph::NodeMap<T> excess(G); 
-
       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.
+      IntMap level(G,n);      
+      TMap excess(G); 
+
+      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(2*n-1);    
       //Stack of the active nodes in level i.
@@ -84 +90 @@
 
       /*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);
+
 
 
@@ -99 +117 @@
       for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e) 
         {
-          if ( capacity.get(e) > 0 ) {
-            NodeIt w=G.head(e);
-            if ( w!=s ) {         
-              if ( excess.get(w) == 0 && w!=t ) stack[level.get(w)].push(w); 
-              flow.set(e, capacity.get(e)); 
-              excess.set(w, excess.get(w)+capacity.get(e));
-            }
-          }
-        }
-
+          if ( capacity.get(e) == 0 ) continue;
+          NodeIt w=G.head(e);
+          if ( w!=s ) {   
+            if ( excess.get(w) == 0 && w!=t ) stack[level.get(w)].push(w); 
+            flow.set(e, capacity.get(e)); 
+            excess.set(w, excess.get(w)+capacity.get(e));
+          }
+        }
+      
       /* 
          End of preprocessing 
@@ -114 +131 @@
 
 
-
       /*
         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 a highest label active node.
-          stack[b].pop();           
-        
-          int newlevel=2*n-2;             //In newlevel we bound 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) {
             
-            if ( flow.get(e) < capacity.get(e) ) {              
-              /*e is an edge of the residual graph */
-
-              NodeIt v=G.head(e);               /*e is the edge wv.*/
-
-              if( level.get(w) == level.get(v)+1 ) {      
-                /*Push is allowed now*/
-
-                if ( excess.get(v)==0 && v != s && v !=t ) stack[level.get(v)].push(v); 
-                /*v becomes active.*/
-
-                if ( capacity.get(e)-flow.get(e) > excess.get(w) ) {       
-                  /*A nonsaturating push.*/
-                  
-                  flow.set(e, flow.get(e)+excess.get(w));
-                  excess.set(v, excess.get(v)+excess.get(w));
-                  excess.set(w,0);
-                  break; 
-
-                } else { 
-                  /*A saturating push.*/
-
-                  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));
-                  if ( excess.get(w)==0 ) break;
-                  /*If w is not active any more, then we go on to the next node.*/
-                  
-                }
-              } else {
-                newlevel = newlevel < level.get(v) ? newlevel : level.get(v);
+            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;
               }
-            
-            } //if the out edge wv is in the res graph 
-         
+            } 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
           
-
-          if ( excess.get(w) > 0 ) {    
-            
-            for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
-              NodeIt v=G.tail(e);  /*e is the edge vw.*/
-
-              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 ( excess.get(v)==0 && v != s && v !=t) stack[level.get(v)].push(v); 
-                  /*v becomes active.*/
-
-                  if ( flow.get(e) > excess.get(w) ) { 
-                    /*A nonsaturating push.*/
-                  
-                    flow.set(e, flow.get(e)-excess.get(w));
-                    excess.set(v, excess.get(v)+excess.get(w));
-                    excess.set(w,0);
-                    break; 
-                  } else {                                               
-                    /*A saturating push.*/
-                    
-                    excess.set(v, excess.get(v)+flow.get(e));
-                    excess.set(w, excess.get(w)-flow.get(e));
-                    flow.set(e,0);
-                    if ( excess.get(w)==0 ) break;
-                  }  
-                } else {
-                  newlevel = newlevel < level.get(v) ? newlevel : level.get(v);
-                }
-                
-              } //if in edge vw is in the res graph 
-
-            } //for in edges vw
-
-          } // if w still has excess after the out edge for cycle
-
-
-          /*
-            Relabel
-          */
+        } // 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);
           
-          if ( excess.get(w) > 0 ) {
-            
-            int oldlevel=level.get(w);      
-            level.set(w,++newlevel);
-
-            if ( oldlevel < n ) {
-              --numb[oldlevel];
-
-              if ( !numb[oldlevel] && oldlevel < A*n ) {  //If the level of w gets empty. 
-                
-                for (EachNodeIt v=G.template first<EachNodeIt>(); v.valid() ; ++v) {
-                  if (level.get(v) > oldlevel && level.get(v) < n ) level.set(v,n);  
-                }
-                for (int i=oldlevel+1 ; i!=n ; ++i) numb[i]=0; 
-                if ( newlevel < n ) newlevel=n; 
-              } else { 
-                if ( newlevel < n ) ++numb[newlevel]; 
+          if ( lev < n ) {
+            --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.get(v) < n ) 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];
+              if ( newlevel < n ) ++numb[newlevel]; 
             }
-            
-            stack[newlevel].push(w);
-            b=newlevel;
-
-          }
-
-        } // if stack[b] is nonempty
-
+          } 
+          
+          stack[newlevel].push(w);
+          b=newlevel;
+          
+        }
+        
       } // while(b)
-
-
+      
+      
       value = excess.get(t);
       /*Max flow value.*/
@@ -272 +281 @@
     */
 
-    T flowonedge(EdgeIt e) {
+    T flowonedge(const EdgeIt e) {
       return flow.get(e);
     }
@@ -282 +291 @@
     */
 
-    typename Graph::EdgeMap<T> allflow() {
+    FlowMap allflow() {
       return flow;
     }
@@ -288 +297 @@
 
 
-    /*
-      Returns a minimum cut by using a reverse bfs from t in the residual graph.
+
+    /*
+      Returns the minimum min cut, by a bfs from s in the residual graph.
     */
     
-    typename Graph::NodeMap<bool> mincut() {
+    template<typename CutMap>
+    void mincut(CutMap& M) {
     
       std::queue<NodeIt> queue;
       
-      mincutvector.set(t,false);      
-      queue.push(t);
+      M.set(s,true);      
+      queue.push(s);
 
       while (!queue.empty()) {
         NodeIt w=queue.front();
         queue.pop();
+        
+        for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
+          NodeIt v=G.head(e);
+          if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
+            queue.push(v);
+            M.set(v, true);
+          }
+        } 
 
         for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
           NodeIt v=G.tail(e);
-          if (mincutvector.get(v) && flow.get(e) < capacity.get(e) ) {
+          if (!M.get(v) && flow.get(e) > 0 ) {
             queue.push(v);
-            mincutvector.set(v, false);
-          }
-        } // for
+            M.set(v, true);
+          }
+        }
+
+      }
+    }
+
+
+
+    /*
+      Returns the maximum min cut, by a reverse bfs 
+      from t in the residual graph.
+    */
+    
+    template<typename CutMap>
+    void max_mincut(CutMap& M) {
+    
+      std::queue<NodeIt> queue;
+      
+      M.set(t,true);        
+      queue.push(t);
+
+      while (!queue.empty()) {
+        NodeIt w=queue.front();
+        queue.pop();
+
+        for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
+          NodeIt v=G.tail(e);
+          if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
+            queue.push(v);
+            M.set(v, true);
+          }
+        }
 
         for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
           NodeIt v=G.head(e);
-          if (mincutvector.get(v) && flow.get(e) > 0 ) {
+          if (!M.get(v) && flow.get(e) > 0 ) {
             queue.push(v);
-            mincutvector.set(v, false);
-          }
-        } // for
-
+            M.set(v, true);
+          }
+        }
       }
 
-      return mincutvector;
-    
-    }
+      for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v) {
+        M.set(v, !M.get(v));
+      }
+
+    }
+
+
+
+    template<typename CutMap>
+    void min_mincut(CutMap& M) {
+      mincut(M);
+    }
+
+
+
   };
 }//namespace marci