diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 786a3d7..193dd63 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -223,6 +223,7 @@
   CERES_TEST(compressed_row_sparse_matrix)
   CERES_TEST(conditioned_cost_function)
   CERES_TEST(corrector)
+  CERES_TEST(cost_function_to_functor)
   CERES_TEST(dense_sparse_matrix)
   CERES_TEST(evaluator)
   CERES_TEST(gradient_checker)
diff --git a/internal/ceres/cost_function_to_functor_test.cc b/internal/ceres/cost_function_to_functor_test.cc
new file mode 100644
index 0000000..8ee02bd
--- /dev/null
+++ b/internal/ceres/cost_function_to_functor_test.cc
@@ -0,0 +1,263 @@
+#include "ceres/cost_function_to_functor.h"
+#include "ceres/autodiff_cost_function.h"
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+const double kTolerance = 1e-18;
+
+void ExpectCostFunctionsAreEqual(const CostFunction& cost_function,
+                                 const CostFunction& actual_cost_function) {
+  EXPECT_EQ(cost_function.num_residuals(), actual_cost_function.num_residuals());
+  const int num_residuals = cost_function.num_residuals();
+  const vector<int16>& parameter_block_sizes = cost_function.parameter_block_sizes();
+  const vector<int16>& actual_parameter_block_sizes  = actual_cost_function.parameter_block_sizes();
+  EXPECT_EQ(parameter_block_sizes.size(), actual_parameter_block_sizes.size());
+
+  int num_parameters = 0;
+  for (int i = 0; i < parameter_block_sizes.size(); ++i) {
+    EXPECT_EQ(parameter_block_sizes[i], actual_parameter_block_sizes[i]);
+    num_parameters += parameter_block_sizes[i];
+  }
+
+  scoped_array<double> parameters(new double[num_parameters]);
+  for (int i = 0; i < num_parameters; ++i) {
+    parameters[i] = static_cast<double>(i) + 1.0;
+  }
+
+  scoped_array<double> residuals(new double[num_residuals]);
+  scoped_array<double> jacobians(new double[num_parameters * num_residuals]);
+
+  scoped_array<double> actual_residuals(new double[num_residuals]);
+  scoped_array<double> actual_jacobians(new double[num_parameters * num_residuals]);
+
+  scoped_array<double*> parameter_blocks(new double*[parameter_block_sizes.size()]);
+  scoped_array<double*> jacobian_blocks(new double*[parameter_block_sizes.size()]);
+  scoped_array<double*> actual_jacobian_blocks(new double*[parameter_block_sizes.size()]);
+
+  num_parameters = 0;
+  for (int i = 0; i < parameter_block_sizes.size(); ++i) {
+    parameter_blocks[i] = parameters.get() + num_parameters;
+    jacobian_blocks[i] = jacobians.get() + num_parameters * num_residuals;
+    actual_jacobian_blocks[i] = actual_jacobians.get() + num_parameters * num_residuals;
+    num_parameters += parameter_block_sizes[i];
+  }
+
+  EXPECT_TRUE(cost_function.Evaluate(parameter_blocks.get(), residuals.get(), NULL));
+  EXPECT_TRUE(actual_cost_function.Evaluate(parameter_blocks.get(), actual_residuals.get(), NULL));
+  for (int i = 0; i < num_residuals; ++i) {
+    EXPECT_NEAR(residuals[i], actual_residuals[i], kTolerance)
+        << "residual id: " << i;
+  }
+
+
+  EXPECT_TRUE(cost_function.Evaluate(parameter_blocks.get(),
+                                     residuals.get(),
+                                     jacobian_blocks.get()));
+  EXPECT_TRUE(actual_cost_function.Evaluate(parameter_blocks.get(),
+                                            actual_residuals.get(),
+                                            actual_jacobian_blocks.get()));
+  for (int i = 0; i < num_residuals; ++i) {
+    EXPECT_NEAR(residuals[i], actual_residuals[i], kTolerance)
+        << "residual : " << i;
+  }
+
+  for (int i = 0; i < num_residuals * num_parameters; ++i) {
+    EXPECT_NEAR(jacobians[i], actual_jacobians[i], kTolerance)
+        << "jacobian : " << i << " " << jacobians[i] << " " << actual_jacobians[i];
+  }
+};
+
+struct OneParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, T* residuals) const {
+    residuals[0] = x1[0] * x1[0];
+    residuals[1] = x1[1] * x1[1];
+    return true;
+  }
+};
+
+struct TwoParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1];
+    return true;
+  }
+};
+
+struct ThreeParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1];
+    return true;
+  }
+};
+
+struct FourParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1];
+    return true;
+  }
+};
+
+struct FiveParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1];
+    return true;
+  }
+};
+
+struct SixParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, const T* x6,  T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0] + x6[0] * x6[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1] + x6[1] * x6[1];
+    return true;
+  }
+};
+
+struct SevenParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, const T* x6, const T* x7, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0] + x6[0] * x6[0] + x7[0] * x7[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1] + x6[1] * x6[1] + x7[1] * x7[1];
+    return true;
+  }
+};
+
+struct EightParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, const T* x6, const T* x7, const T* x8,
+                  T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0] + x6[0] * x6[0] + x7[0] * x7[0]
+        + x8[0] * x8[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1] + x6[1] * x6[1] + x7[1] * x7[1]
+        + x8[1] * x8[1];
+    return true;
+  }
+};
+
+struct NineParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, const T* x6, const T* x7, const T* x8,
+                  const T* x9, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0] + x6[0] * x6[0] + x7[0] * x7[0]
+        + x8[0] * x8[0] + x9[0] * x9[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1] + x6[1] * x6[1] + x7[1] * x7[1]
+        + x8[1] * x8[1] + x9[1] * x9[1];
+    return true;
+  }
+};
+
+struct TenParameterBlockFunctor {
+ public:
+  template <typename T>
+  bool operator()(const T* x1, const T* x2, const T* x3, const T* x4,
+                  const T* x5, const T* x6, const T* x7, const T* x8,
+                  const T* x9, const T* x10, T* residuals) const {
+    residuals[0] = x1[0] * x1[0]  + x2[0] * x2[0] + x3[0] * x3[0]
+        + x4[0] * x4[0] + x5[0] * x5[0] + x6[0] * x6[0] + x7[0] * x7[0]
+        + x8[0] * x8[0] + x9[0] * x9[0] + x10[0] * x10[0];
+    residuals[1] = x1[1] * x1[1]  + x2[1] * x2[1] + x3[1] * x3[1]
+        + x4[1] * x4[1] + x5[1] * x5[1] + x6[1] * x6[1] + x7[1] * x7[1]
+        + x8[1] * x8[1] + x9[1] * x9[1] + x10[1] * x10[1];
+    return true;
+  }
+};
+
+#define TEST_BODY(NAME)                                                 \
+  TEST(CostFunctionToFunctor, NAME){                                    \
+    scoped_ptr<CostFunction> cost_function(                             \
+        new AutoDiffCostFunction<                                       \
+            CostFunctionToFunctor<2, PARAMETER_BLOCK_SIZES >,           \
+                2, PARAMETER_BLOCK_SIZES>(new CostFunctionToFunctor<    \
+                    2, PARAMETER_BLOCK_SIZES >(                         \
+                        new AutoDiffCostFunction<                       \
+                            NAME##Functor, 2, PARAMETER_BLOCK_SIZES >(  \
+                  new NAME##Functor))));                                \
+                                                                        \
+scoped_ptr<CostFunction> actual_cost_function(                          \
+    new AutoDiffCostFunction<NAME##Functor, 2, PARAMETER_BLOCK_SIZES >( \
+        new NAME##Functor));                                            \
+ExpectCostFunctionsAreEqual(*cost_function, *actual_cost_function);     \
+}
+
+#define PARAMETER_BLOCK_SIZES 2
+TEST_BODY(OneParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2
+TEST_BODY(TwoParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2
+TEST_BODY(ThreeParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2
+TEST_BODY(FourParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2
+TEST_BODY(FiveParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2,2
+TEST_BODY(SixParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2,2,2
+TEST_BODY(SevenParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2,2,2,2
+TEST_BODY(EightParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2,2,2,2,2
+TEST_BODY(NineParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#define PARAMETER_BLOCK_SIZES 2,2,2,2,2,2,2,2,2,2
+TEST_BODY(TenParameterBlock)
+#undef PARAMETER_BLOCK_SIZES
+
+#undef TEST_BODY
+
+
+}  // namespace internal
+}  // namespace ceres