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diff --git a/internal/ceres/iterative_refiner_test.cc b/internal/ceres/iterative_refiner_test.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2018 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: sameeragarwal@google.com (Sameer Agarwal)
+
+#include "ceres/iterative_refiner.h"
+
+#include "Eigen/Dense"
+#include "ceres/internal/eigen.h"
+#include "ceres/sparse_cholesky.h"
+#include "ceres/sparse_matrix.h"
+#include "glog/logging.h"
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+// Macros to help us define virtual methods which we do not expect to
+// use/call in this test.
+#define DO_NOT_CALL \
+  { LOG(FATAL) << "DO NOT CALL"; }
+#define DO_NOT_CALL_WITH_RETURN(x) \
+  {                                \
+    LOG(FATAL) << "DO NOT CALL";   \
+    return x;                      \
+  }
+
+// A fake SparseMatrix, which uses an Eigen matrix to do the real work.
+class FakeSparseMatrix : public SparseMatrix {
+ public:
+  FakeSparseMatrix(const Matrix& m) : m_(m) {}
+  virtual ~FakeSparseMatrix() {}
+
+  // y += Ax
+  virtual void RightMultiply(const double* x, double* y) const {
+    VectorRef(y, m_.cols()) += m_ * ConstVectorRef(x, m_.cols());
+  }
+  // y += A'x
+  virtual void LeftMultiply(const double* x, double* y) const {
+    // We will assume that this is a symmetric matrix.
+    RightMultiply(x, y);
+  }
+
+  virtual double* mutable_values() { return m_.data(); }
+  virtual const double* values() const { return m_.data(); }
+  virtual int num_rows() const { return m_.cols(); }
+  virtual int num_cols() const { return m_.cols(); }
+  virtual int num_nonzeros() const { return m_.cols() * m_.cols(); }
+
+  // The following methods are not needed for tests in this file.
+  virtual void SquaredColumnNorm(double* x) const DO_NOT_CALL;
+  virtual void ScaleColumns(const double* scale) DO_NOT_CALL;
+  virtual void SetZero() DO_NOT_CALL;
+  virtual void ToDenseMatrix(Matrix* dense_matrix) const DO_NOT_CALL;
+  virtual void ToTextFile(FILE* file) const DO_NOT_CALL;
+
+ private:
+  Matrix m_;
+};
+
+// A fake SparseCholesky which uses Eigen's Cholesky factorization to
+// do the real work. The template parameter allows us to work in
+// doubles or floats, even though the source matrix is double.
+template <typename Scalar>
+class FakeSparseCholesky : public SparseCholesky {
+ public:
+  FakeSparseCholesky(const Matrix& lhs) { lhs_ = lhs.cast<Scalar>(); }
+  virtual ~FakeSparseCholesky() {}
+
+  virtual LinearSolverTerminationType Solve(const double* rhs_ptr,
+                                            double* solution_ptr,
+                                            std::string* message) {
+    const int num_cols = lhs_.cols();
+    VectorRef solution(solution_ptr, num_cols);
+    ConstVectorRef rhs(rhs_ptr, num_cols);
+    solution = lhs_.llt().solve(rhs.cast<Scalar>()).template cast<double>();
+    return LINEAR_SOLVER_SUCCESS;
+  }
+
+  // The following methods are not needed for tests in this file.
+  virtual CompressedRowSparseMatrix::StorageType StorageType() const
+      DO_NOT_CALL_WITH_RETURN(CompressedRowSparseMatrix::UPPER_TRIANGULAR);
+  virtual LinearSolverTerminationType Factorize(CompressedRowSparseMatrix* lhs,
+                                                std::string* message)
+      DO_NOT_CALL_WITH_RETURN(LINEAR_SOLVER_FAILURE);
+
+  virtual LinearSolverTerminationType FactorAndSolve(
+      CompressedRowSparseMatrix* lhs,
+      const double* rhs,
+      double* solution,
+      std::string* message) DO_NOT_CALL_WITH_RETURN(LINEAR_SOLVER_FAILURE);
+
+ private:
+  Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic> lhs_;
+};
+
+#undef DO_NOT_CALL
+#undef DO_NOT_CALL_WITH_RETURN
+
+class IterativeRefinerTest : public ::testing::Test {
+ public:
+  void SetUp() {
+    num_cols_ = 5;
+    max_num_iterations_ = 30;
+    Matrix m(num_cols_, num_cols_);
+    m.setRandom();
+    lhs_ = m * m.transpose();
+    solution_.resize(num_cols_);
+    solution_.setRandom();
+    rhs_ = lhs_ * solution_;
+  };
+
+ protected:
+  int num_cols_;
+  int max_num_iterations_;
+  Matrix lhs_;
+  Vector rhs_, solution_;
+};
+
+TEST_F(IterativeRefinerTest, RandomSolutionWithExactFactorizationConverges) {
+  FakeSparseMatrix lhs(lhs_);
+  FakeSparseCholesky<double> sparse_cholesky(lhs_);
+  IterativeRefiner refiner(max_num_iterations_);
+  Vector refined_solution(num_cols_);
+  refined_solution.setRandom();
+  refiner.Refine(lhs, rhs_.data(), &sparse_cholesky, refined_solution.data());
+  EXPECT_NEAR((lhs_ * refined_solution - rhs_).norm(),
+              0.0,
+              std::numeric_limits<double>::epsilon() * 10);
+}
+
+TEST_F(IterativeRefinerTest,
+       RandomSolutionWithApproximationFactorizationConverges) {
+  FakeSparseMatrix lhs(lhs_);
+  // Use a single precision Cholesky factorization of the double
+  // precision matrix. This will give us an approximate factorization.
+  FakeSparseCholesky<float> sparse_cholesky(lhs_);
+  IterativeRefiner refiner(max_num_iterations_);
+  Vector refined_solution(num_cols_);
+  refined_solution.setRandom();
+  refiner.Refine(lhs, rhs_.data(), &sparse_cholesky, refined_solution.data());
+  EXPECT_NEAR((lhs_ * refined_solution - rhs_).norm(),
+              0.0,
+              std::numeric_limits<double>::epsilon() * 10);
+}
+
+}  // namespace internal
+}  // namespace ceres