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2  Presolve
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8  Presolve
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12  Presolve
13  </h2></div></div></div><p>
14  The header file for the use of CLP's presolve functionality is
15  <tt class="filename">COIN/Clp/include/Presolve.hpp</tt>.  The sample program below
16  illustrates some of the possibilities offered by CLP's presolve:
17  </p><div class="example"><a name="presolveexample"></a><p class="title"><b>Example 2.3. Presolve code fragment</b></p><pre class="programlisting">
18#include "ClpSimplex.hpp"
19#include "ClpPresolve.hpp"
20int main (int argc, const char *argv[])
22  ClpSimplex model;
23  model.readMps("../../Mps/Sample/p0033.mps"); // initialized by readMps or whatever
24  ClpPresolve presolveInfo;
25  ClpSimplex * presolvedModel = presolveInfo.presolvedModel(model);
26  // at this point we have original model and a new model.  The  information
27  // on the operations done is in presolveInfo
28  if (presolvedModel) {
29    // was not found to be infeasible - so lets solve
30    // if presolvedModel was NULL then it was primal infeasible and ...
31    presolvedModel-&gt;dual(); // or whatever else we wish to do
32    presolveInfo.postsolve(true);  // the true updates status arrays in original       
33    /* If the presolved model was optimal then so should the
34       original be.           
35       We can use checkSolution and test feasibility */
36    model.checkSolution();         
37    if (model.numberDualInfeasibilities()||
38        model.numberPrimalInfeasibilities())
39      printf("%g dual %g(%d) Primal %g(%d)\n",
40             model.objectiveValue(),
41             model.sumDualInfeasibilities(),
42             model.numberDualInfeasibilities(),
43             model.sumPrimalInfeasibilities(),
44             model.numberPrimalInfeasibilities());
45    // Due to tolerances we can not guarantee that so you may wish to throw in
46    model.primal(1);
47  }
49  </pre></div><p>
50  Presolve has a few more options which can be found in the header file, for
51  example whether to treat as an integer problem or whether to keep row and
52  column names.
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54  Simplex-specific Methods
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