ext/OGDF/src/graphalg/mcf_front_reinelt.cpp

   1 /*
   2  * $Revision: 2552 $
   3  *
   4  * last checkin:
   5  *   $Author: gutwenger $
   6  *   $Date: 2012-07-05 16:45:20 +0200 (Do, 05. Jul 2012) $
   7  ***************************************************************/
   8
   9 /** \file
  10  * \brief front-end for min-most flow algorithm (Reinelt)
  11  *
  12  * \author Carsten Gutwenger
  13  *
  14  * \par License:
  15  * This file is part of the Open Graph Drawing Framework (OGDF).
  16  *
  17  * \par
  18  * Copyright (C)<br>
  19  * See README.txt in the root directory of the OGDF installation for details.
  20  *
  21  * \par
  22  * This program is free software; you can redistribute it and/or
  23  * modify it under the terms of the GNU General Public License
  24  * Version 2 or 3 as published by the Free Software Foundation;
  25  * see the file LICENSE.txt included in the packaging of this file
  26  * for details.
  27  *
  28  * \par
  29  * This program is distributed in the hope that it will be useful,
  30  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  31  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  32  * GNU General Public License for more details.
  33  *
  34  * \par
  35  * You should have received a copy of the GNU General Public
  36  * License along with this program; if not, write to the Free
  37  * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  38  * Boston, MA 02110-1301, USA.
  39  *
  40  * \see  http://www.gnu.org/copyleft/gpl.html
  41  ***************************************************************/
  42
  43
  44 #include <ogdf/graphalg/MinCostFlowReinelt.h>
  45 #include <ogdf/basic/NodeArray.h>
  46 #include <ogdf/basic/EdgeArray.h>
  47
  48
  49
  50
  51 namespace ogdf {
  52
  53 bool MinCostFlowReinelt::call(
  54         const Graph &G,
  55         const EdgeArray<int> &lowerBound,
  56         const EdgeArray<int> &upperBound,
  57         const EdgeArray<int> &cost,
  58         const NodeArray<int> &supply,
  59         EdgeArray<int> &flow)
  60 {
  61         NodeArray<int> dual(G);
  62         return call(G, lowerBound, upperBound, cost, supply, flow, dual);
  63 }
  64
  65
  66 // computes min-cost-flow
  67 // returns true if a minimum cost flow could be found
  68 bool MinCostFlowReinelt::call(
  69         const Graph &G,
  70         const EdgeArray<int> &lowerBound,
  71         const EdgeArray<int> &upperBound,
  72         const EdgeArray<int> &cost,
  73         const NodeArray<int> &supply,
  74         EdgeArray<int> &flow,
  75         NodeArray<int> &dual)
  76 {
  77         OGDF_ASSERT(checkProblem(G,lowerBound,upperBound,supply) == true);
  78
  79         const int n = G.numberOfNodes();
  80         const int m = G.numberOfEdges();
  81
  82         // assign indices 0, ..., n-1 to nodes in G
  83         // (this is not guaranteed for v->index() )
  84         NodeArray<int> vIndex(G);
  85         // assigning supply
  86         Array<int> mcfSupply(n);
  87
  88         node v;
  89         int i = 0;
  90         forall_nodes(v, G) {
  91                 mcfSupply[i] = supply[v];
  92                 vIndex[v] = ++i;
  93         }
  94
  95
  96         // allocation of arrays for arcs
  97         Array<int> mcfTail(m);
  98         Array<int> mcfHead(m);
  99         Array<int> mcfLb(m);
 100         Array<int> mcfUb(m);
 101         Array<int> mcfCost(m);
 102         Array<int> mcfFlow(m);
 103         Array<int> mcfDual(n+1); // dual[n] = dual variable of root struct
 104
 105         // set input data in edge arrays
 106         int nSelfLoops = 0;
 107         i = 0;
 108         edge e;
 109         forall_edges(e, G)
 110         {
 111                 // We handle self-loops in the network already in the front-end
 112                 // (they are just set to the lower bound below when copying result)
 113                 if(e->isSelfLoop()) {
 114                         nSelfLoops++;
 115                         continue;
 116                 }
 117
 118                 mcfTail[i] = vIndex[e->source()];
 119                 mcfHead[i] = vIndex[e->target()];
 120                 mcfLb  [i] = lowerBound[e];
 121                 mcfUb  [i] = upperBound[e];
 122                 mcfCost[i] = cost[e];
 123
 124                 ++i;
 125         }
 126
 127
 128         int retCode; // return (error or success) code
 129         int objVal;  // value of flow
 130
 131         // call actual min-cost-flow function
 132         // mcf does not support single nodes
 133         if ( n > 1)
 134         {
 135                 //mcf does not support single edges
 136                 if (m < 2)
 137                 {
 138                         if ( m == 1)
 139                         {
 140                                 e = G.firstEdge();
 141                                 flow[e] = lowerBound[e];
 142                         }
 143                         retCode = 0;
 144                 }
 145                 else retCode = mcf(n, m-nSelfLoops, mcfSupply, mcfTail, mcfHead, mcfLb, mcfUb,
 146                         mcfCost, mcfFlow, mcfDual, &objVal);
 147         }
 148         else retCode = 0;
 149
 150
 151         // copy resulting flow for return
 152         i = 0;
 153         forall_edges(e, G)
 154         {
 155                 if(e->isSelfLoop()) {
 156                         flow[e] = lowerBound[e];
 157                         continue;
 158                 }
 159
 160                 flow[e] = mcfFlow[i];
 161                 if (retCode == 0) {
 162                         OGDF_ASSERT( (flow[e]>=lowerBound[e]) && (flow[e]<= upperBound[e]) )
 163                 }
 164                 ++i;
 165         }
 166
 167         // copy resulting dual values for return
 168         i = 0;
 169         forall_nodes(v, G) {
 170                 dual[v] = mcfDual[i];
 171                 ++i;
 172         }
 173
 174         // successful if retCode == 0
 175         return (retCode == 0);
 176 }
 177
 178
 179 } // end namespace ogdf
 180