json/example_01.cpp

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// @HEADER
// *****************************************************************************
//               Rapid Optimization Library (ROL) Package
//
// Copyright 2014 NTESS and the ROL contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

 
#include "ROL_Algorithm.hpp"
#include "ROL_StdVector.hpp"
#include "ROL_Zakharov.hpp"
 
#include "example_01.hpp"
 
#include "ROL_Stream.hpp"
#include "ROL_GlobalMPISession.hpp"
#include "ROL_XMLReader.hpp"
 
typedef double RealT;
 
int main(int argc, char *argv[]) {
 
  ROL::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;
 
}