Changeset 1514:c9b9bc63db4e in lemon0.x for doc/quicktour.dox
 Timestamp:
 06/24/05 23:03:08 (16 years ago)
 Branch:
 default
 Phase:
 public
 Convert:
 svn:c9d7d8f590d60310b91f818b3a526b0e/lemon/trunk@1998
 File:

 1 edited
Legend:
 Unmodified
 Added
 Removed

doc/quicktour.dox
r1511 r1514 19 19 about \ref graphs "graphs". 20 20 21 You will also want to assign data to the edges or nodes of the graph, for example a length or capacity function defined on the edges. You can do this in LEMON using so called \ref maps "maps". You can define a map on the nodes or on the edges of the graph and the value of the map (the range of the function) can be practically almost of any type. Read more about maps \ref mapspage "here". 21 You will also want to assign data to the edges or nodes of the graph, for 22 example a length or capacity function defined on the edges. You can do this in 23 LEMON using so called \b maps. You can define a map on the nodes or on the edges of the graph and the value of the map (the range of the function) can be practically almost of any type. Read more about maps \ref mapspage "here". 22 24 23 25 Some examples are the following (you will find links next to the code fragments that help to download full demo programs: save them on your computer and compile them according to the description in the page about \ref getsart How to start using LEMON): 24 26 25  First we give two examples that show how to instantiate a graph. The 27 <ul> 28 <li> First we give two examples that show how to instantiate a graph. The 26 29 first one shows the methods that add nodes and edges, but one will 27 30 usually use the second way which reads a graph from a stream (file). 28 # The following code fragment shows how to fill a graph with data. It creates a complete graph on 4 nodes. The type Listgraph is one of the LEMON graph types: the typedefs in the beginning are for convenience and we will suppose them later as well. 31 <ol> 32 <li>The following code fragment shows how to fill a graph with data. It creates a complete graph on 4 nodes. The type Listgraph is one of the LEMON graph types: the typedefs in the beginning are for convenience and we will suppose them later as well. 29 33 \code 30 34 typedef ListGraph Graph; … … 43 47 See the whole program in file \ref helloworld.cc. 44 48 45 If you want to read more on the LEMON graph structures and concepts, read the page about \ref graphs "graphs".46 47 #The following code shows how to read a graph from a stream (e.g. a file). LEMON supports the DIMACS file format: it can read a graph instance from a file49 If you want to read more on the LEMON graph structures and concepts, read the page about \ref graphs "graphs". 50 51 <li> The following code shows how to read a graph from a stream (e.g. a file). LEMON supports the DIMACS file format: it can read a graph instance from a file 48 52 in that format (find the documentation of the DIMACS file format on the web). 49 53 \code … … 54 58 One can also store network (graph+capacity on the edges) instances and other things in DIMACS format and use these in LEMON: to see the details read the documentation of the \ref dimacs.h "Dimacs file format reader". 55 59 56 57 If you want to solve some transportation problems in a network then60 </ol> 61 <li> If you want to solve some transportation problems in a network then 58 62 you will want to find shortest paths between nodes of a graph. This is 59 63 usually solved using Dijkstra's algorithm. A utility … … 130 134 131 135 132 If you want to design a network and want to minimize the total length136 <li> If you want to design a network and want to minimize the total length 133 137 of wires then you might be looking for a <b>minimum spanning tree</b> in 134 138 an undirected graph. This can be found using the Kruskal algorithm: the … … 138 142 Ide Zsuzska fog irni! 139 143 140  144 <li>Many problems in network optimization can be formalized by means of a 145 linear programming problem (LP problem, for short). In our library we decided 146 not to write an LP solver, since such packages are available in the commercial 147 world just as well as in the open source world, and it is also a difficult 148 task to compete these. Instead we decided to develop an interface that makes 149 it easier to use these solvers together with LEMON. So far we have an 150 interface for the commercial LP solver software \b CLPLEX (developed by ILOG) 151 and for the open source solver \b GLPK (a shorthand for Gnu Linear Programming 152 Toolkit). 153 154 We will show two examples, the first one shows how simple it is to formalize 155 and solve an LP problem in LEMON, while the second one shows how LEMON 156 facilitates solving network optimization problems using LP solvers. 157 158 <ol> 159 <li>The following code shows how to solve an LP problem using the LEMON lp 160 interface. 141 161 142 162 \code 143 163 164 //A default solver is taken 165 LpDefault lp; 166 typedef LpDefault::Row Row; 167 typedef LpDefault::Col Col; 168 169 170 //This will be a maximization 171 lp.max(); 172 173 //We add coloumns (variables) to our problem 174 Col x1 = lp.addCol(); 175 Col x2 = lp.addCol(); 176 Col x3 = lp.addCol(); 177 178 //Constraints 179 lp.addRow(x1+x2+x3 <=100); 180 lp.addRow(10*x1+4*x2+5*x3<=600); 181 lp.addRow(2*x1+2*x2+6*x3<=300); 182 //Nonnegativity of the variables 183 lp.colLowerBound(x1, 0); 184 lp.colLowerBound(x2, 0); 185 lp.colLowerBound(x3, 0); 186 //Objective function 187 lp.setObj(10*x1+6*x2+4*x3); 188 189 //Call the routine of the underlying LP solver 190 lp.solve(); 191 192 //Print results 193 if (lp.primalStatus()==LpSolverBase::OPTIMAL){ 194 printf("Z = %g; x1 = %g; x2 = %g; x3 = %g\n", 195 lp.primalValue(), 196 lp.primal(x1), lp.primal(x2), lp.primal(x3)); 197 } 198 else{ 199 std::cout<<"Optimal solution not found!"<<std::endl; 200 } 201 202 144 203 \endcode 145 204 205 See the whole code in \ref lp_demo.cc. 206 207 <li>The second example shows how easy it is to formalize a network 208 optimization problem as an LP problem using the LEMON LP interface. 209 210 </ol> 211 </ul> 146 212 147 213 */
Note: See TracChangeset
for help on using the changeset viewer.