# HG changeset patch
# User Alpar Juttner <alpar@cs.elte.hu>
# Date 2011-02-25 21:37:47
# Node ID 30d5f950aa5f4347b3bef4e9ab7c01c3eb8f05c7
# Parent  bb70ad62c95fd75d6bd134451a406df9bd0eda12

Fix wrong initialization in Preflow (#414)

diff --git a/lemon/preflow.h b/lemon/preflow.h
--- a/lemon/preflow.h
+++ b/lemon/preflow.h
@@ -525,9 +525,6 @@
           if ((*_level)[u] == _level->maxLevel()) continue;
           _flow->set(e, (*_capacity)[e]);
           (*_excess)[u] += rem;
-          if (u != _target && !_level->active(u)) {
-            _level->activate(u);
-          }
         }
       }
       for (InArcIt e(_graph, _source); e != INVALID; ++e) {
@@ -537,11 +534,12 @@
           if ((*_level)[v] == _level->maxLevel()) continue;
           _flow->set(e, 0);
           (*_excess)[v] += rem;
-          if (v != _target && !_level->active(v)) {
-            _level->activate(v);
-          }
         }
       }
+      for (NodeIt n(_graph); n != INVALID; ++n) 
+        if(n!=_source && n!=_target && _tolerance.positive((*_excess)[n]))
+          _level->activate(n);
+          
       return true;
     }
 
diff --git a/test/preflow_test.cc b/test/preflow_test.cc
--- a/test/preflow_test.cc
+++ b/test/preflow_test.cc
@@ -151,6 +151,30 @@
   return true;
 }
 
+void initFlowTest()
+{
+  DIGRAPH_TYPEDEFS(SmartDigraph);
+  
+  SmartDigraph g;
+  SmartDigraph::ArcMap<int> cap(g),iflow(g);
+  Node s=g.addNode(); Node t=g.addNode();
+  Node n1=g.addNode(); Node n2=g.addNode();
+  Arc a;
+  a=g.addArc(s,n1); cap[a]=20; iflow[a]=20;
+  a=g.addArc(n1,n2); cap[a]=10; iflow[a]=0;
+  a=g.addArc(n2,t); cap[a]=20; iflow[a]=0;
+
+  Preflow<SmartDigraph> pre(g,cap,s,t);
+  pre.init(iflow);
+  pre.startFirstPhase();
+  check(pre.flowValue() == 10, "The incorrect max flow value.");
+  check(pre.minCut(s), "Wrong min cut (Node s).");
+  check(pre.minCut(n1), "Wrong min cut (Node n1).");
+  check(!pre.minCut(n2), "Wrong min cut (Node n2).");
+  check(!pre.minCut(t), "Wrong min cut (Node t).");
+}
+
+
 int main() {
 
   typedef SmartDigraph Digraph;
@@ -241,5 +265,7 @@
   check(preflow_test.flowValue() == min_cut_value,
         "The max flow value or the three min cut values are incorrect.");
 
+  initFlowTest();
+  
   return 0;
 }