Hello Ceres！Hello World！

Ceres官网教程给出的例程中，求解的问题是求

使得

取到最小值。

源文件helloworld.cc的内容为：

#include<iostream>
#include<ceres/ceres.h>

using namespace std;
using namespace ceres;

struct CostFunctor {
   template <typename T>
   bool operator()(const T* const x, T* residual) const {
     residual[0] = T(10.0) - x[0];
     return true;
   }
};

int main(int argc, char** argv) {
  google::InitGoogleLogging(argv[0]);

  double initial_x = 5.0;
  double x = initial_x;

  Problem problem;
  CostFunction* cost_function =
      new AutoDiffCostFunction<CostFunctor, 1, 1>(new CostFunctor);
  problem.AddResidualBlock(cost_function, NULL, &x);

  Solver::Options options;
  options.linear_solver_type = ceres::DENSE_QR;
  options.minimizer_progress_to_stdout = true;
  Solver::Summary summary;
  Solve(options, &problem, &summary);

  std::cout << summary.BriefReport() << "\n";
  std::cout << "x : " << initial_x
            << " -> " << x << "\n";
  return 0;
}
           

CMakeLists.txt内容为

cmake_minimum_required(VERSION 2.8)

project(helloworld)

find_package(Ceres REQUIRED)
include_directories(${CERES_INCLUDE_DIRS})

# helloworld
add_executable(helloworld helloworld.cc)
target_link_libraries(helloworld ${CERES_LIBRARIES})
           

cmake和make编译之后，./helloworld执行，终端输出为：

iter      cost      cost_change  |gradient|   |step|    tr_ratio  tr_radius  ls_iter  iter_time  total_time
   0  1.250000e+01    0.00e+00    5.00e+00   0.00e+00   0.00e+00  1.00e+04        0    2.29e-05    5.21e-05
   1  1.249750e-07    1.25e+01    5.00e-04   5.00e+00   1.00e+00  3.00e+04        1    4.17e-05    1.39e-04
   2  1.388518e-16    1.25e-07    1.67e-08   5.00e-04   1.00e+00  9.00e+04        1    1.00e-05    1.57e-04
Ceres Solver Report: Iterations: 3, Initial cost: 1.250000e+01, Final cost: 1.388518e-16, Termination: CONVERGENCE
x : 5 -> 10