Merge pull request #74 from clue/fix-algo-minimumcostflow

Fix Algorithm\MinimumCostFlow

CHANGELOG.md

@@ -36,7 +36,12 @@ you spot any mistakes.
 *   Fix: Throwing an `UnexpectedValueException` if writing GraphViz Dot script
     to a temporary file fails and remove its debugging output
     ([#77](https://github.com/clue/graph/issues/77) and [#78](https://github.com/clue/graph/issues/78) @Metabor)
-
+
+*   Fix: The `Algorithm\MinimumCostFlow` algorithms now work again. The reference
+    to a non-existant class has been updated. Also fixed several issues with
+    regards to special cases such as disconnected or undirected graphs.
+    ([#74](https://github.com/clue/graph/issues/74)
+
 *   BC break: Remove unneeded alias definitions of `getVertexFirst()`,
     `getVertexSource()` and `getVertexTarget()`
     [#76]https://github.com/clue/graph/issues/76)):

lib/Fhaculty/Graph/Algorithm/MinimumCostFlow/Base.php

@@ -4,6 +4,7 @@
 
 use Fhaculty\Graph\Algorithm\BaseGraph;
 use Fhaculty\Graph\Algorithm\Weight as AlgorithmWeight;
+use Fhaculty\Graph\Algorithm\Flow as AlgorithmFlow;
 use Fhaculty\Graph\Exception\UnderflowException;
 use Fhaculty\Graph\Edge\Base as Edge;
 use Fhaculty\Graph\Set\Edges;
@@ -20,7 +21,9 @@ abstract class Base extends BaseGraph
      */
     protected function checkBalance()
     {
-        $balance = $this->graph->getBalance();
+        $alg = new AlgorithmFlow($this->graph);
+        $balance = $alg->getBalance();
+
         $tolerance = 0.000001;
         if ($balance >= $tolerance || $balance <= -$tolerance) {
             throw new UnexpectedValueException('The given graph is not balanced value is: ' . $balance);

lib/Fhaculty/Graph/Algorithm/MinimumCostFlow/CycleCanceling.php

@@ -2,11 +2,8 @@
 
 namespace Fhaculty\Graph\Algorithm\MinimumCostFlow;
 
-
 use Fhaculty\Graph\Exception\UnexpectedValueException;
-
 use Fhaculty\Graph\Exception\UnderflowException;
-
 use Fhaculty\Graph\Edge\Base as Edge;
 use Fhaculty\Graph\Set\Edges;
 use Fhaculty\Graph\Algorithm\MaxFlow\EdmondsKarp as MaxFlowEdmondsKarp;
@@ -29,17 +26,16 @@ public function createGraph()
 
         // connect supersource s* and supersink t* with all "normal" sources and sinks
         foreach ($resultGraph->getVertices() as $vertex) {
-            // $vertex->getFlow();
-            $flow = $vertex->getBalance();
-            $b = abs($vertex->getBalance());
-            // source
-            if ($flow > 0) {
-                $superSource->createEdgeTo($vertex)->setCapacity($b);
-
-                $sumBalance += $flow;
-            // sink
-            } elseif ($flow < 0) {
-                $vertex->createEdgeTo($superSink)->setCapacity($b);
+            $balance = $vertex->getBalance();
+
+            if ($balance > 0) {
+                // positive balance => source capacity
+                $superSource->createEdgeTo($vertex)->setCapacity($balance);
+
+                $sumBalance += $balance;
+            } elseif ($balance < 0) {
+                // negative balance => sink capacity (positive)
+                $vertex->createEdgeTo($superSink)->setCapacity(-$balance);
             }
         }
 
@@ -62,8 +58,8 @@ public function createGraph()
             $alg = new DetectNegativeCycle($residualGraph);
             try {
                 $clonedEdges = $alg->getCycleNegative()->getEdges();
-            // no negative cycle found => end algorithm
             } catch (UnderflowException $ignore) {
+                // no negative cycle found => end algorithm
                 break;
             }
 

lib/Fhaculty/Graph/Algorithm/MinimumCostFlow/SuccessiveShortestPath.php

@@ -3,11 +3,8 @@
 namespace Fhaculty\Graph\Algorithm\MinimumCostFlow;
 
 use Fhaculty\Graph\Exception\DomainException;
-
 use Fhaculty\Graph\Exception\UnderflowException;
-
 use Fhaculty\Graph\Exception\UnexpectedValueException;
-
 use Fhaculty\Graph\Graph;
 use Fhaculty\Graph\Vertex;
 use Fhaculty\Graph\Edge\Base as Edge;
@@ -21,10 +18,9 @@ class SuccessiveShortestPath extends Base
 {
     /**
      * @uses Graph::createGraphClone()
-     * @uses AlgorithmResidualGraph::createGraph()
-     * @uses AlgorithmSpMooreBellmanFord::getEdgesTo(Vertex $targetVertex)
-     *
-     * @see AlgorithmMCF::createGraph()
+     * @uses ResidualGraph::createGraph()
+     * @uses SpMooreBellmanFord::getEdgesTo(Vertex $targetVertex)
+     * @see Base::createGraph()
      */
     public function createGraph()
     {
@@ -40,29 +36,29 @@ public function createGraph()
         // initial flow of edges
         $edges = $resultGraph->getEdges();
         foreach ($edges as $edge) {
-            // 0 if weight of edge is positiv
+            if (!($edge instanceof EdgeDirected)) {
+                throw new UnexpectedValueException('Undirected edges are not supported for SuccessiveShortestPath');
+            }
+
+            // 0 if weight of edge is positive
             $flow = 0;
 
             // maximal flow if weight of edge is negative
             if ($edge->getWeight() < 0) {
                 $flow = $edge->getCapacity();
 
-                if ($edge instanceof EdgeDirected) {
-                    $startVertex = $edge->getVertexStart();
-                    $endVertex = $edge->getVertexEnd();
+                $startVertex = $edge->getVertexStart();
+                $endVertex = $edge->getVertexEnd();
 
-                    // add balance to start- and end-vertex
-                    $this->addBalance($startVertex, $flow);
-                    $this->addBalance($endVertex, - $flow);
-                } else {
-                    throw new UnexpectedValueException('Undirected Edges not suported');
-                }
+                // add balance to start- and end-vertex
+                $this->addBalance($startVertex, $flow);
+                $this->addBalance($endVertex, - $flow);
             }
 
             $edge->setFlow($flow);
         }
 
-        // return or Exception insite this while
+        // return or Exception inside this while
         while (true) {
             // create residual graph
             $algRG = new ResidualGraph($resultGraph);
@@ -71,25 +67,25 @@ public function createGraph()
             // search for a source
             try {
                 $sourceVertex = $this->getVertexSource($residualGraph);
-            // if no source is found the minimum-cost flow is found
             } catch (UnderflowException $ignore) {
+                // no source is found => minimum-cost flow is found
                 break;
             }
 
-            // search for reachble sink from this source
+            // search for reachable target sink from this source
             try {
                 $targetVertex = $this->getVertexSink($sourceVertex);
-            // if no target is found the network has not enough capacity
-            } catch (UnderflowException $ignore) {
-                throw new UnexpectedValueException('The graph has not enough capacity for the minimum-cost flow');
+            } catch (UnderflowException $e) {
+                // no target found => network does not have enough capacity
+                throw new UnexpectedValueException('The graph has not enough capacity for the minimum-cost flow', 0, $e);
             }
 
             // calculate shortest path between source- and target-vertex
             $algSP = new SpMooreBellmanFord($sourceVertex);
             $edgesOnFlow = $algSP->getEdgesTo($targetVertex);
 
             // calculate the maximal possible flow
-                                                                                // new flow is the maximal possible flow for this path
+            // new flow is the maximal possible flow for this path
             $newflow    =    $this->graph->getVertex($sourceVertex->getId())->getBalance() - $sourceVertex->getBalance();
             $targetFlow = - ($this->graph->getVertex($targetVertex->getId())->getBalance() - $targetVertex->getBalance());
 
@@ -107,7 +103,7 @@ public function createGraph()
             // add the new flow to the path
             $this->addFlow($resultGraph, $edgesOnFlow, $newflow);
 
-            // add balance to source and remove for the sink
+            // add balance to source and remove for the target sink
             $oriSourceVertex = $resultGraph->getVertex($sourceVertex->getId());
             $oriTargetVertex = $resultGraph->getVertex($targetVertex->getId());
 
@@ -118,29 +114,6 @@ public function createGraph()
         return $resultGraph;
     }
 
-    /**
-     * check if balance on each vertex of the given graph matches the original graph's
-     *
-     * @param  Graph     $graph
-     * @return boolean
-     * @throws Exception if given graph is not a clone of the original graph (each vertex has to be present in both graphs)
-     * @uses Graph::getBalanace()
-     * @uses Graph::getVertex()
-     */
-    private function isBalanceReached(Graph $graph)
-    {
-        if (count($graph->getVertices()) !== count($this->graph->getVertices())) {
-            throw new DomainException('Given graph does not appear to be a clone of input graph');
-        }
-        foreach ($this->graph->getVertices()->getMap() as $vid => $vertex) {
-            if ($vertex->getBalance() !== $graph->getVertex($vid)->getBalance()) {
-                return false;
-            }
-        }
-
-        return true;
-    }
-
     /**
      *
      *