Changeset 2629:84354c78b068 in lemon-0.x for lemon/cost_scaling.h

Timestamp:

11/13/08 16:29:04 (12 years ago)

Author:

Peter Kovacs

Branch:

default

Phase:

public

Convert:

svn:c9d7d8f5-90d6-0310-b91f-818b3a526b0e/lemon/trunk@3514

Message:

Improved constructors for min cost flow classes
Removing the non-zero lower bounds is faster

File:

• lemon/cost_scaling.h (modified) (2 diffs)

lemon/cost_scaling.h

@@ -201 +201 @@
                  const CostMap &cost,
                  const SupplyMap &supply ) :
-      _graph(graph), _lower(&lower), _capacity(graph), _orig_cost(cost),
-      _cost(graph), _supply(graph), _flow(NULL), _local_flow(false),
+      _graph(graph), _lower(&lower), _capacity(capacity), _orig_cost(cost),
+      _cost(graph), _supply(supply), _flow(NULL), _local_flow(false),
       _potential(NULL), _local_potential(false), _res_cost(_cost),
       _res_graph(NULL), _red_cost(NULL), _excess(graph, 0)
     {
+      // Check the sum of supply values
+      Supply sum = 0;
+      for (NodeIt n(_graph); n != INVALID; ++n) sum += _supply[n];
+      _valid_supply = sum == 0;
+
       // Remove non-zero lower bounds
-      _capacity = subMap(capacity, lower);
-      Supply sum = 0;
-      for (NodeIt n(_graph); n != INVALID; ++n) {
-        Supply s = supply[n];
-        for (InEdgeIt e(_graph, n); e != INVALID; ++e)
-          s += lower[e];
-        for (OutEdgeIt e(_graph, n); e != INVALID; ++e)
-          s -= lower[e];
-        _supply[n] = s;
-        sum += s;
-      }
-      _valid_supply = sum == 0;
+      for (EdgeIt e(_graph); e != INVALID; ++e) {
+        if (lower[e] != 0) {
+          _capacity[e] -= lower[e];
+          _supply[_graph.source(e)] -= lower[e];
+          _supply[_graph.target(e)] += lower[e];
+        }
+      }
     }
 
@@ -262 +262 @@
                  Node s, Node t,
                  Supply flow_value ) :
-      _graph(graph), _lower(&lower), _capacity(graph), _orig_cost(cost),
-      _cost(graph), _supply(graph), _flow(NULL), _local_flow(false),
+      _graph(graph), _lower(&lower), _capacity(capacity), _orig_cost(cost),
+      _cost(graph), _supply(graph, 0), _flow(NULL), _local_flow(false),
       _potential(NULL), _local_potential(false), _res_cost(_cost),
       _res_graph(NULL), _red_cost(NULL), _excess(graph, 0)
     {
-      // Remove nonzero lower bounds
-      _capacity = subMap(capacity, lower);
-      for (NodeIt n(_graph); n != INVALID; ++n) {
-        Supply sum = 0;
-        if (n == s) sum =  flow_value;
-        if (n == t) sum = -flow_value;
-        for (InEdgeIt e(_graph, n); e != INVALID; ++e)
-          sum += lower[e];
-        for (OutEdgeIt e(_graph, n); e != INVALID; ++e)
-          sum -= lower[e];
-        _supply[n] = sum;
+      // Remove non-zero lower bounds
+      _supply[s] =  flow_value;
+      _supply[t] = -flow_value;
+      for (EdgeIt e(_graph); e != INVALID; ++e) {
+        if (lower[e] != 0) {
+          _capacity[e] -= lower[e];
+          _supply[_graph.source(e)] -= lower[e];
+          _supply[_graph.target(e)] += lower[e];
+        }
       }
       _valid_supply = true;