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| 2 | Presolve |
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| 8 | Presolve |
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| 10 | Basic Model Classes |
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| 12 | Presolve |
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| 13 | </h2></div></div></div><p> |
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| 14 | The header file for the use of CLP's presolve functionality is |
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| 15 | <tt class="filename">COIN/Clp/include/Presolve.hpp</tt>. The sample program below |
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| 16 | illustrates some of the possibilities offered by CLP's presolve: |
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| 17 | </p><div class="example"><a name="presolveexample"></a><p class="title"><b>Example 2.3. Presolve code fragment</b></p><pre class="programlisting"> |
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| 18 | #include "ClpSimplex.hpp" |
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| 19 | #include "ClpPresolve.hpp" |
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| 20 | int main (int argc, const char *argv[]) |
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| 21 | { |
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| 22 | ClpSimplex model; |
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| 23 | model.readMps("../../Mps/Sample/p0033.mps"); // initialized by readMps or whatever |
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| 24 | ClpPresolve presolveInfo; |
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| 25 | ClpSimplex * presolvedModel = presolveInfo.presolvedModel(model); |
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| 26 | // at this point we have original model and a new model. The information |
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| 27 | // on the operations done is in presolveInfo |
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| 28 | if (presolvedModel) { |
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| 29 | // was not found to be infeasible - so lets solve |
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| 30 | // if presolvedModel was NULL then it was primal infeasible and ... |
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| 31 | presolvedModel->dual(); // or whatever else we wish to do |
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| 32 | presolveInfo.postsolve(true); // the true updates status arrays in original |
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| 33 | /* If the presolved model was optimal then so should the |
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| 34 | original be. |
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| 35 | We can use checkSolution and test feasibility */ |
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| 36 | model.checkSolution(); |
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| 37 | if (model.numberDualInfeasibilities()|| |
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| 38 | model.numberPrimalInfeasibilities()) |
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| 39 | printf("%g dual %g(%d) Primal %g(%d)\n", |
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| 40 | model.objectiveValue(), |
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| 41 | model.sumDualInfeasibilities(), |
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| 42 | model.numberDualInfeasibilities(), |
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| 43 | model.sumPrimalInfeasibilities(), |
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| 44 | model.numberPrimalInfeasibilities()); |
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| 45 | // Due to tolerances we can not guarantee that so you may wish to throw in |
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| 46 | model.primal(1); |
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| 47 | } |
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| 48 | } |
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| 49 | </pre></div><p> |
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| 50 | Presolve has a few more options which can be found in the header file, for |
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| 51 | example whether to treat as an integer problem or whether to keep row and |
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| 52 | column names. |
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| 53 | </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch02s07.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch02s09.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"> |
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| 54 | Simplex-specific Methods |
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