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43 
44 /*! \file  example_01.cpp
45     \brief Shows how to minimize Rosenbrock's function using Newton-Krylov.
46     \addtogroup examples_group
47 */
48 
49 #define USE_HESSVEC 1
50 
51 #include "ROL_Rosenbrock.hpp"
52 #include "ROL_Algorithm.hpp"
53 #include "ROL_LineSearchStep.hpp"
54 #include "ROL_StatusTest.hpp"
55 #include "ROL_Stream.hpp"
56 #include "Teuchos_GlobalMPISession.hpp"
57 
58 #include <iostream>
59 
60 typedef double RealT;
61 
main(int argc,char * argv[])62 int main(int argc, char *argv[]) {
63 
64   Teuchos::GlobalMPISession mpiSession(&argc, &argv);
65 
66   // This little trick lets us print to std::cout only if a (dummy) command-line argument is provided.
67   int iprint     = argc - 1;
68   ROL::Ptr<std::ostream> outStream;
69   ROL::nullstream bhs; // outputs nothing
70   if (iprint > 0)
71     outStream = ROL::makePtrFromRef(std::cout);
72   else
73     outStream = ROL::makePtrFromRef(bhs);
74 
75   int errorFlag  = 0;
76 
77   // *** Example body.
78 
79   try {
80 
81     ROL::ZOO::Objective_Rosenbrock<RealT> obj;
82     int dim = 100; // Set problem dimension. Must be even.
83 
84     // Set parameters.
85     ROL::ParameterList parlist;
86     parlist.sublist("Step").sublist("Line Search").sublist("Descent Method").set("Type", "Newton-Krylov");
87     parlist.sublist("Status Test").set("Gradient Tolerance",1.e-12);
88     parlist.sublist("Status Test").set("Step Tolerance",1.e-14);
89     parlist.sublist("Status Test").set("Iteration Limit",100);
90 
91     // Define algorithm.
92     ROL::Ptr<ROL::Step<RealT>>
93       step = ROL::makePtr<ROL::LineSearchStep<RealT>>(parlist);
94     ROL::Ptr<ROL::StatusTest<RealT>>
95       status = ROL::makePtr<ROL::StatusTest<RealT>>(parlist);
96     ROL::Algorithm<RealT> algo(step,status,false);
97 
98     // Iteration Vector
99     ROL::Ptr<std::vector<RealT> > x_ptr = ROL::makePtr<std::vector<RealT>>(dim, 0.0);
100     // Set Initial Guess
101     for (int i=0; i<dim/2; i++) {
102       (*x_ptr)[2*i]   = -1.2;
103       (*x_ptr)[2*i+1] =  1.0;
104     }
105     ROL::StdVector<RealT> x(x_ptr);
106 
107     // Run Algorithm
108     algo.run(x, obj, true, *outStream);
109 
110     // Get True Solution
111     ROL::Ptr<std::vector<RealT> > xtrue_ptr = ROL::makePtr<std::vector<RealT>>(dim, 1.0);
112     ROL::StdVector<RealT> xtrue(xtrue_ptr);
113 
114     // Compute Error
115     x.axpy(-1.0, xtrue);
116     RealT abserr = x.norm();
117     RealT relerr = abserr/xtrue.norm();
118     *outStream << std::scientific << "\n   Absolute Error: " << abserr;
119     *outStream << std::scientific << "\n   Relative Error: " << relerr << "\n";
120     if ( relerr > sqrt(ROL::ROL_EPSILON<RealT>()) ) {
121       errorFlag += 1;
122     }
123   }
124   catch (std::logic_error& err) {
125     *outStream << err.what() << "\n";
126     errorFlag = -1000;
127   }; // end try
128 
129   if (errorFlag != 0)
130     std::cout << "End Result: TEST FAILED\n";
131   else
132     std::cout << "End Result: TEST PASSED\n";
133 
134   return 0;
135 
136 }
137 
138