The header file for the use of CLP's presolve functionality is COIN/Clp/include/Presolve.hpp. The sample program below illustrates some of the possibilities offered by CLP's presolve:

Example 2.3. Presolve code fragment

#include "ClpSimplex.hpp"
#include "ClpPresolve.hpp"
int main (int argc, const char *argv[])
  ClpSimplex model; 
  model.readMps("../../Mps/Sample/p0033.mps"); // initialized by readMps or whatever 
  ClpPresolve presolveInfo; 
  ClpSimplex * presolvedModel = presolveInfo.presolvedModel(model); 
  // at this point we have original model and a new model.  The  information
  // on the operations done is in presolveInfo 
  if (presolvedModel) { 
    // was not found to be infeasible - so lets solve 
    // if presolvedModel was NULL then it was primal infeasible and ... 
    presolvedModel->dual(); // or whatever else we wish to do 
    presolveInfo.postsolve(true);  // the true updates status arrays in original       
    /* If the presolved model was optimal then so should the 
       original be.           
       We can use checkSolution and test feasibility */ 
    if (model.numberDualInfeasibilities()|| 
      printf("%g dual %g(%d) Primal %g(%d)\n", 
    // Due to tolerances we can not guarantee that so you may wish to throw in

Presolve has a few more options which can be found in the header file, for example whether to treat as an integer problem or whether to keep row and column names.