Changeset 635:933f593824c2 in lemon-0.x for src/work/athos/mincostflow.h

Timestamp:

05/13/04 19:42:23 (20 years ago)

Author:

athos

Branch:

default

Phase:

public

Convert:

svn:c9d7d8f5-90d6-0310-b91f-818b3a526b0e/lemon/trunk@826

Message:

Started mincostflow.

File:

• src/work/athos/mincostflow.h (modified) (9 diffs)

src/work/athos/mincostflow.h

@@ -37 +37 @@
   ///
   ///\author Attila Bernath
-  template <typename Graph, typename LengthMap, typename SupplyMap>
+  template <typename Graph, typename LengthMap, typename SupplyDemandMap>
   class MinCostFlow {
 
@@ -43 +43 @@
 
 
-    typedef typename SupplyMap::ValueType Supply;
+    typedef typename SupplyDemandMap::ValueType SupplyDemand;
     
     typedef typename Graph::Node Node;
@@ -85 +85 @@
     const Graph& G;
     const LengthMap& length;
-    const SupplyMap& supply;//supply or demand of nodes
+    const SupplyDemandMap& supply_demand;//supply or demand of nodes
 
 
@@ -95 +95 @@
     typename Graph::template NodeMap<Length> potential;
     //To store excess-deficit values
-    SupplyMap excess;
+    SupplyDemandMap excess_deficit;
     
 
@@ -104 +104 @@
 
 
-    MinCostFlow(Graph& _G, LengthMap& _length, SupplyMap& _supply) : G(_G), 
-      length(_length), supply(_supply), flow(_G), potential(_G){ }
+    MinCostFlow(Graph& _G, LengthMap& _length, SupplyDemandMap& _supply_demand) : G(_G), 
+      length(_length), supply_demand(_supply_demand), flow(_G), potential(_G){ }
 
     
@@ -111 +111 @@
 
     ///Runs the algorithm.
-    ///Returns k if there are at least k edge-disjoint paths from s to t.
-    ///Otherwise it returns the number of found edge-disjoint paths from s to t.
+
     ///\todo May be it does make sense to be able to start with a nonzero 
     /// feasible primal-dual solution pair as well.
@@ -118 +117 @@
 
       //Resetting variables from previous runs
-      total_length = 0;
+      //total_length = 0;
+
+      typedef typename Graph::template NodeMap<int> HeapMap;
+      typedef Heap<Node, SupplyDemand, typename Graph::template NodeMap<int>,
+        std::greater<SupplyDemand> >    HeapType;
+
+      //A heap for the excess nodes
+      HeapMap excess_nodes_map(G,-1);
+      HeapType excess_nodes(excess_nodes_map);
+
+      //A heap for the deficit nodes
+      HeapMap deficit_nodes_map(G,-1);
+      HeapType deficit_nodes(deficit_nodes_map);
+
       
       FOR_EACH_LOC(typename Graph::EdgeIt, e, G){
@@ -125 +137 @@
 
       //Initial value for delta
-      Supply delta = 0;
-      
+      SupplyDemand delta = 0;
+
       FOR_EACH_LOC(typename Graph::NodeIt, n, G){
-        if (delta < abs(supply[e])){
-          delta = abs(supply[e]);
-        }
-        excess.set(n,supply[e]);
+        excess_deficit.set(n,supply_demand[n]);
+        //A supply node
+        if (excess_deficit[n] > 0){
+          excess_nodes.push(n,excess_deficit[n]);
+        }
+        //A demand node
+        if (excess_deficit[n] < 0){
+          deficit_nodes.push(n, - excess_deficit[n]);
+        }
+        //Finding out starting value of delta
+        if (delta < abs(excess_deficit[n])){
+          delta = abs(excess_deficit[n]);
+        }
         //Initialize the copy of the Dijkstra potential to zero
         potential.set(n,0);
       }
-      
-
+
+      //It'll be allright as an initial value, though this value 
+      //can be the maximum deficit here
+      SupplyDemand max_excess = delta;
       
       //We need a residual graph which is uncapacitated
@@ -148 +171 @@
 
 
-      int i;
-      for (i=0; i<k; ++i){
-        dijkstra.run(s);
-        if (!dijkstra.reached(t)){
-          //There are no k paths from s to t
-          break;
-        };
+      while (max_excess > 0){
+
         
-        //We have to copy the potential
-        FOR_EACH_LOC(typename ResGraphType::NodeIt, n, res_graph){
-          potential[n] += dijkstra.distMap()[n];
+        //Merge and stuff
+
+        Node s = excess_nodes.top(); 
+        SupplyDemand max_excess = excess_nodes[s];
+        Node t = deficit_nodes.top(); 
+        if (max_excess < dificit_nodes[t]){
+          max_excess = dificit_nodes[t];
+        }
+
+
+        while(max_excess > ){
+
+          
+          //s es t valasztasa
+
+          //Dijkstra part       
+          dijkstra.run(s);
+
+          /*We know from theory that t can be reached
+          if (!dijkstra.reached(t)){
+            //There are no k paths from s to t
+            break;
+          };
+          */
+          
+          //We have to change the potential
+          FOR_EACH_LOC(typename ResGraphType::NodeIt, n, res_graph){
+            potential[n] += dijkstra.distMap()[n];
+          }
+
+
+          //Augmenting on the sortest path
+          Node n=t;
+          ResGraphEdge e;
+          while (n!=s){
+            e = dijkstra.pred(n);
+            n = dijkstra.predNode(n);
+            res_graph.augment(e,delta);
+            /*
+            //Let's update the total length
+            if (res_graph.forward(e))
+              total_length += length[e];
+            else 
+              total_length -= length[e];            
+            */
+          }
+
+          //Update the excess_nodes heap
+          if (delta >= excess_nodes[s]){
+            if (delta > excess_nodes[s])
+              deficit_nodes.push(s,delta - excess_nodes[s]);
+            excess_nodes.pop();
+            
+          } 
+          else{
+            excess_nodes[s] -= delta;
+          }
+          //Update the deficit_nodes heap
+          if (delta >= deficit_nodes[t]){
+            if (delta > deficit_nodes[t])
+              excess_nodes.push(t,delta - deficit_nodes[t]);
+            deficit_nodes.pop();
+            
+          } 
+          else{
+            deficit_nodes[t] -= delta;
+          }
+          //Dijkstra part ends here
         }
 
         /*
-        {
-
-          typename ResGraphType::NodeIt n;
-          for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) {
-              potential[n] += dijkstra.distMap()[n];
-          }
-        }
+         * End of the delta scaling phase 
         */
 
-        //Augmenting on the sortest path
-        Node n=t;
-        ResGraphEdge e;
-        while (n!=s){
-          e = dijkstra.pred(n);
-          n = dijkstra.predNode(n);
-          res_graph.augment(e,delta);
-          //Let's update the total length
-          if (res_graph.forward(e))
-            total_length += length[e];
-          else 
-            total_length -= length[e];      
-        }
-
+        //Whatever this means
+        delta = delta / 2;
+
+        /*This is not necessary here
+        //Update the max_excess
+        max_excess = 0;
+        FOR_EACH_LOC(typename Graph::NodeIt, n, G){
+          if (max_excess < excess_deficit[n]){
+            max_excess = excess_deficit[n];
+          }
+        }
+        */
+        //Reset delta if still too big
+        if (8*number_of_nodes*max_excess <= delta){
+          delta = max_excess;
           
-      }
+        }
+          
+      }//while(max_excess > 0)