Add a small test to make sure GradientProblemSolver works correctly.

The test makes sure the Rosenbrock function is correctly minimized from the
canonical starting point using the default settings.

Change-Id: Iea820f976707bde37162981c5db87fac5167ba9e

internal/ceres/CMakeLists.txt

diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 3108634..f3df974 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -263,6 +263,7 @@
   CERES_TEST(gradient_checker)
   CERES_TEST(gradient_checking_cost_function)
   CERES_TEST(gradient_problem)
+  CERES_TEST(gradient_problem_solver)
   CERES_TEST(graph)
   CERES_TEST(graph_algorithms)
   CERES_TEST(householder_vector)

internal/ceres/gradient_problem_solver_test.cc

diff --git a/internal/ceres/gradient_problem_solver_test.cc b/internal/ceres/gradient_problem_solver_test.cc
new file mode 100644
index 0000000..d6332ae
--- /dev/null
+++ b/internal/ceres/gradient_problem_solver_test.cc
@@ -0,0 +1,76 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: strandmark@google.com (Petter Strandmark)
+
+#include "ceres/gradient_problem.h"
+#include "ceres/gradient_problem_solver.h"
+
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+// Rosenbrock function; see http://en.wikipedia.org/wiki/Rosenbrock_function .
+class Rosenbrock : public ceres::FirstOrderFunction {
+ public:
+  virtual ~Rosenbrock() {}
+
+  virtual bool Evaluate(const double* parameters,
+                        double* cost,
+                        double* gradient) const {
+    const double x = parameters[0];
+    const double y = parameters[1];
+
+    cost[0] = (1.0 - x) * (1.0 - x) + 100.0 * (y - x * x) * (y - x * x);
+    if (gradient != NULL) {
+      gradient[0] = -2.0 * (1.0 - x) - 200.0 * (y - x * x) * 2.0 * x;
+      gradient[1] = 200.0 * (y - x * x);
+    }
+    return true;
+  }
+
+  virtual int NumParameters() const { return 2; }
+};
+
+TEST(GradientProblemSolver, SolvesRosenbrockWithDefaultOptions) {
+  const double expected_tolerance = 1e-9;
+  double parameters[2] = {-1.2, 0.0};
+
+  ceres::GradientProblemSolver::Options options;
+  ceres::GradientProblemSolver::Summary summary;
+  ceres::GradientProblem problem(new Rosenbrock());
+  ceres::Solve(options, problem, parameters, &summary);
+
+  EXPECT_EQ(CONVERGENCE, summary.termination_type);
+  EXPECT_NEAR(1.0, parameters[0], expected_tolerance);
+  EXPECT_NEAR(1.0, parameters[1], expected_tolerance);
+}
+
+}  // namespace internal
+}  // namespace ceres