json/example_01.cpp

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#include "ROL_Algorithm.hpp"
#include "ROL_StdVector.hpp"
#include "ROL_Zakharov.hpp"

#include "example_01.hpp"

#include "ROL_Stream.hpp"
#include "Teuchos_GlobalMPISession.hpp"
#include "Teuchos_XMLParameterListHelpers.hpp"

typedef double RealT;

int main(int argc, char *argv[]) {

  Teuchos::GlobalMPISession mpiSession(&argc, &argv);

  // This little trick lets us print to std::cout only if a (dummy) command-line argument is provided.
  int iprint     = argc - 1;
  ROL::Ptr<std::ostream> outStream;
  ROL::nullstream bhs; // outputs nothing
  if (iprint > 0)
    outStream = ROL::makePtrFromRef(std::cout);
  else
    outStream = ROL::makePtrFromRef(bhs);

  int errorFlag  = 0;

  // *** Example body.

  try {

    int dim = 10;

    ROL::ParameterList parlist;

    std::string jsonFileName("parameters.json");
    parlist.setName("Imported from " + jsonFileName);
    
    // Load json parameters into a ROL::ParameterList  
    ROL::JSON_Parameters(jsonFileName,parlist);
    std::string stepname = "Trust Region"; // can we obtain this from parlist?  or jsonFile?

    ROL::StepFactory<RealT> stepFactory;
    ROL::Ptr<ROL::Step<RealT> > step = stepFactory.getStep(stepname, parlist);

    // Define Status Test
    RealT gtol  = parlist.get("Gradient Tolerance",1e-12); 
    RealT stol  = parlist.get("Step Tolerance",1e-14);  
    int   maxit = parlist.get("Maximum Number of Iterations",100); 
    ROL::Ptr<ROL::StatusTest<RealT> > status = ROL::makePtr<ROL::StatusTest<RealT>>(gtol, stol, maxit);           

    ROL::Algorithm<RealT> algo(step,status,false);

    ROL::Ptr<std::vector<RealT> > x_ptr = ROL::makePtr<std::vector<RealT>>(dim, 1.0);
    ROL::Ptr<std::vector<RealT> > k_ptr = ROL::makePtr<std::vector<RealT>>(dim, 0.0);

    ROL::StdVector<RealT> x(x_ptr);
    ROL::Ptr<ROL::Vector<RealT> > k = ROL::makePtr<ROL::StdVector<RealT>>(k_ptr);

    for(int i=0;i<dim;++i) {
        (*k_ptr)[i] = i+1.0;
    }
 
    ROL::ZOO::Objective_Zakharov<RealT> obj(k);

    // Run Algorithm
    algo.run(x, obj, true, *outStream);

    // Get True Solution
    ROL::Ptr<std::vector<RealT> > xtrue_ptr = ROL::makePtr<std::vector<RealT>>(dim, 0.0);
    ROL::StdVector<RealT> xtrue(xtrue_ptr);

    // Compute Error
    x.axpy(-1.0, xtrue);
    RealT abserr = x.norm();
    *outStream << std::scientific << "\n   Absolute Error: " << abserr;
    if ( abserr > sqrt(ROL::ROL_EPSILON<RealT>())) ) {
      errorFlag += 1;
    }

    // Make an XML file containing the supplied parameters
    Teuchos::writeParameterListToXmlFile(parlist,"parameters.xml");
 
 }
  catch (std::logic_error& err) {
    *outStream << err.what() << "\n";
    errorFlag = -1000;
  }; // end try

  if (errorFlag != 0)
    std::cout << "End Result: TEST FAILED\n";
  else
    std::cout << "End Result: TEST PASSED\n";

  return 0;

}