diff --git a/examples/nist.cc b/examples/nist.cc
index f12dbf3..3944586 100644
--- a/examples/nist.cc
+++ b/examples/nist.cc
@@ -99,6 +99,9 @@
               "dense_qr",
               "Options are: sparse_cholesky, dense_qr, dense_normal_cholesky "
               "and cgnr");
+DEFINE_string(dense_linear_algebra_library,
+              "eigen",
+              "Options are: eigen and lapack.");
 DEFINE_string(preconditioner, "jacobi", "Options are: identity, jacobi");
 DEFINE_string(line_search,
               "wolfe",
@@ -466,6 +469,9 @@
                                      &options->minimizer_type));
   CHECK(ceres::StringToLinearSolverType(CERES_GET_FLAG(FLAGS_linear_solver),
                                         &options->linear_solver_type));
+  CHECK(StringToDenseLinearAlgebraLibraryType(
+      CERES_GET_FLAG(FLAGS_dense_linear_algebra_library),
+      &options->dense_linear_algebra_library_type));
   CHECK(ceres::StringToPreconditionerType(CERES_GET_FLAG(FLAGS_preconditioner),
                                           &options->preconditioner_type));
   CHECK(ceres::StringToTrustRegionStrategyType(
diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 5d9e0ab..957d476 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -74,6 +74,7 @@
     cxsparse.cc
     dense_cholesky.cc
     dense_normal_cholesky_solver.cc
+    dense_qr.cc
     dense_qr_solver.cc
     dense_sparse_matrix.cc
     detect_structure.cc
@@ -97,7 +98,6 @@
     iterative_refiner.cc
     iterative_schur_complement_solver.cc
     levenberg_marquardt_strategy.cc
-    lapack.cc
     line_search.cc
     line_search_direction.cc
     line_search_minimizer.cc
@@ -455,6 +455,7 @@
   ceres_test(cubic_interpolation)
   ceres_test(dense_linear_solver)
   ceres_test(dense_cholesky)
+  ceres_test(dense_qr)
   ceres_test(dense_sparse_matrix)
   ceres_test(detect_structure)
   ceres_test(dogleg_strategy)
diff --git a/internal/ceres/dense_jacobian_writer.h b/internal/ceres/dense_jacobian_writer.h
index 1d7187c..efecf35 100644
--- a/internal/ceres/dense_jacobian_writer.h
+++ b/internal/ceres/dense_jacobian_writer.h
@@ -59,8 +59,8 @@
   }
 
   SparseMatrix* CreateJacobian() const {
-    return new DenseSparseMatrix(
-        program_->NumResiduals(), program_->NumEffectiveParameters(), true);
+    return new DenseSparseMatrix(program_->NumResiduals(),
+                                 program_->NumEffectiveParameters());
   }
 
   void Write(int residual_id,
@@ -86,10 +86,10 @@
       ConstMatrixRef parameter_jacobian(
           jacobians[j], num_residuals, parameter_block_size);
 
-      dense_jacobian->mutable_matrix().block(residual_offset,
-                                             parameter_block->delta_offset(),
-                                             num_residuals,
-                                             parameter_block_size) =
+      dense_jacobian->mutable_matrix()->block(residual_offset,
+                                              parameter_block->delta_offset(),
+                                              num_residuals,
+                                              parameter_block_size) =
           parameter_jacobian;
     }
   }
diff --git a/internal/ceres/dense_linear_solver_benchmark.cc b/internal/ceres/dense_linear_solver_benchmark.cc
index fa0d034..b8f1e00 100644
--- a/internal/ceres/dense_linear_solver_benchmark.cc
+++ b/internal/ceres/dense_linear_solver_benchmark.cc
@@ -43,10 +43,8 @@
 static void BM_DenseSolver(benchmark::State& state) {
   const int num_rows = state.range(0);
   const int num_cols = state.range(1);
-  constexpr bool kReserveDiagonal = true;
-
-  DenseSparseMatrix jacobian(num_rows, num_cols, kReserveDiagonal);
-  jacobian.mutable_matrix() = Eigen::MatrixXd::Random(num_rows, num_cols);
+  DenseSparseMatrix jacobian(num_rows, num_cols);
+  *jacobian.mutable_matrix() = Eigen::MatrixXd::Random(num_rows, num_cols);
   Eigen::VectorXd rhs = Eigen::VectorXd::Random(num_rows, 1);
 
   Eigen::VectorXd solution(num_cols);
diff --git a/internal/ceres/dense_linear_solver_test.cc b/internal/ceres/dense_linear_solver_test.cc
index 419ec3e..4dff5af 100644
--- a/internal/ceres/dense_linear_solver_test.cc
+++ b/internal/ceres/dense_linear_solver_test.cc
@@ -89,24 +89,22 @@
       solver->Solve(&lhs, rhs.data(), per_solve_options, solution.data());
   EXPECT_EQ(summary.termination_type, LINEAR_SOLVER_SUCCESS);
 
-  // If solving for the regularized solution, add the diagonal to the
-  // matrix. This makes subsequent computations simpler.
-  if (testing::get<2>(param)) {
-    lhs.AppendDiagonal(problem->D.get());
-  };
+  Vector normal_rhs = lhs.matrix().transpose() * rhs.head(num_rows);
+  Matrix normal_lhs = lhs.matrix().transpose() * lhs.matrix();
 
-  Vector tmp = Vector::Zero(num_rows + num_cols);
-  lhs.RightMultiply(solution.data(), tmp.data());
-  Vector actual_normal_rhs = Vector::Zero(num_cols);
-  lhs.LeftMultiply(tmp.data(), actual_normal_rhs.data());
+  if (regularized) {
+    ConstVectorRef diagonal(problem->D.get(), num_cols);
+    normal_lhs += diagonal.array().square().matrix().asDiagonal();
+  }
 
-  Vector expected_normal_rhs = Vector::Zero(num_cols);
-  lhs.LeftMultiply(rhs.data(), expected_normal_rhs.data());
-  const double residual = (expected_normal_rhs - actual_normal_rhs).norm() /
-                          expected_normal_rhs.norm();
+  Vector actual_normal_rhs = normal_lhs * solution;
 
-  EXPECT_NEAR(residual, 0.0, 10 * std::numeric_limits<double>::epsilon())
-      << "\nexpected: " << expected_normal_rhs.transpose()
+  const double normalized_residual =
+      (normal_rhs - actual_normal_rhs).norm() / normal_rhs.norm();
+
+  EXPECT_NEAR(
+      normalized_residual, 0.0, 10 * std::numeric_limits<double>::epsilon())
+      << "\nexpected: " << normal_rhs.transpose()
       << "\nactual: " << actual_normal_rhs.transpose();
 }
 
diff --git a/internal/ceres/dense_normal_cholesky_solver.cc b/internal/ceres/dense_normal_cholesky_solver.cc
index 73e5bf8..b208d58 100644
--- a/internal/ceres/dense_normal_cholesky_solver.cc
+++ b/internal/ceres/dense_normal_cholesky_solver.cc
@@ -57,7 +57,6 @@
   const int num_rows = A->num_rows();
   const int num_cols = A->num_cols();
 
-  ConstColMajorMatrixRef Aref = A->matrix();
   Matrix lhs(num_cols, num_cols);
   lhs.setZero();
 
@@ -68,10 +67,10 @@
   // Using rankUpdate instead of GEMM, exposes the fact that its the
   // same matrix being multiplied with itself and that the product is
   // symmetric.
-  lhs.selfadjointView<Eigen::Upper>().rankUpdate(Aref.transpose());
+  lhs.selfadjointView<Eigen::Upper>().rankUpdate(A->matrix().transpose());
 
   //   rhs = A'b
-  Vector rhs = Aref.transpose() * ConstVectorRef(b, num_rows);
+  Vector rhs = A->matrix().transpose() * ConstVectorRef(b, num_rows);
 
   if (per_solve_options.D != NULL) {
     ConstVectorRef D(per_solve_options.D, num_cols);
diff --git a/internal/ceres/dense_qr.cc b/internal/ceres/dense_qr.cc
new file mode 100644
index 0000000..9c0b24e
--- /dev/null
+++ b/internal/ceres/dense_qr.cc
@@ -0,0 +1,297 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2022 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/dense_qr.h"
+
+#include <algorithm>
+#include <memory>
+
+#ifndef CERES_NO_LAPACK
+
+// LAPACK routines for solving a linear least squares problem using QR
+// factorization. This is done in three stages:
+//
+// A * x     = b
+// Q * R * x = b               (dgeqrf)
+//     R * x = Q' * b          (dormqr)
+//         x = R^{-1} * Q'* b  (dtrtrs)
+
+// clang-format off
+
+// Compute the QR factorization of a.
+//
+// a is an m x n column major matrix (Denoted by "A" in the above description)
+// lda is the leading dimension of a. lda >= max(1, num_rows)
+// tau is an array of size min(m,n). It contains the scalar factors of the
+// elementary reflectors.
+// work is an array of size max(1,lwork). On exit, if info=0, work[0] contains
+// the optimal size of work.
+//
+// if lwork >= 1 it is the size of work. If lwork = -1, then a workspace query is assumed.
+// dgeqrf computes the optimal size of the work array and returns it as work[0].
+//
+// info = 0, successful exit.
+// info < 0, if info = -i, then the i^th argument had illegal value.
+extern "C" void dgeqrf_(const int* m, const int* n, double* a, const int* lda,
+                        double* tau, double* work, const int* lwork, int* info);
+
+// Apply Q or Q' to b.
+//
+// b is a m times n column major matrix.
+// size = 'L' applies Q or Q' on the left, size = 'R' applies Q or Q' on the right.
+// trans = 'N', applies Q, trans = 'T', applies Q'.
+// k is the number of elementary reflectors whose product defines the matrix Q.
+// If size = 'L', m >= k >= 0 and if side = 'R', n >= k >= 0.
+// a is an lda x k column major matrix containing the reflectors as returned by dgeqrf.
+// ldb is the leading dimension of b.
+// work is an array of size max(1, lwork)
+// lwork if positive is the size of work. If lwork = -1, then a
+// workspace query is assumed.
+//
+// info = 0, successful exit.
+// info < 0, if info = -i, then the i^th argument had illegal value.
+extern "C" void dormqr_(const char* side, const char* trans, const int* m,
+                        const int* n ,const int* k, double* a, const int* lda,
+                        double* tau, double* b, const int* ldb, double* work,
+                        const int* lwork, int* info);
+
+// Solve a triangular system of the form A * x = b
+//
+// uplo = 'U', A is upper triangular. uplo = 'L' is lower triangular.
+// trans = 'N', 'T', 'C' specifies the form  - A, A^T, A^H.
+// DIAG = 'N', A is not unit triangular. 'U' is unit triangular.
+// n is the order of the matrix A.
+// nrhs number of columns of b.
+// a is a column major lda x n.
+// b is a column major matrix of ldb x nrhs
+//
+// info = 0 succesful.
+//      = -i < 0 i^th argument is an illegal value.
+//      = i > 0, i^th diagonal element of A is zero.
+extern "C" void dtrtrs_(const char* uplo, const char* trans, const char* diag,
+                        const int* n, const int* nrhs, double* a, const int* lda,
+                        double* b, const int* ldb, int* info);
+// clang-format on
+
+#endif
+
+namespace ceres {
+namespace internal {
+
+std::unique_ptr<DenseQR> DenseQR::Create(const LinearSolver::Options& options) {
+  std::unique_ptr<DenseQR> dense_qr;
+
+  switch (options.dense_linear_algebra_library_type) {
+    case EIGEN:
+      dense_qr = std::make_unique<EigenDenseQR>();
+      break;
+
+    case LAPACK:
+#ifndef CERES_NO_LAPACK
+      dense_qr = std::make_unique<LAPACKDenseQR>();
+      break;
+#else
+      LOG(FATAL) << "Ceres was compiled without support for LAPACK.";
+#endif
+
+    default:
+      LOG(FATAL) << "Unknown dense linear algebra library type : "
+                 << DenseLinearAlgebraLibraryTypeToString(
+                        options.dense_linear_algebra_library_type);
+  }
+  return dense_qr;
+}
+
+LinearSolverTerminationType DenseQR::FactorAndSolve(int num_rows,
+                                                    int num_cols,
+                                                    double* lhs,
+                                                    const double* rhs,
+                                                    double* solution,
+                                                    std::string* message) {
+  LinearSolverTerminationType termination_type =
+      Factorize(num_rows, num_cols, lhs, message);
+  if (termination_type == LINEAR_SOLVER_SUCCESS) {
+    termination_type = Solve(rhs, solution, message);
+  }
+  return termination_type;
+}
+
+LinearSolverTerminationType EigenDenseQR::Factorize(int num_rows,
+                                                    int num_cols,
+                                                    double* lhs,
+                                                    std::string* message) {
+  Eigen::Map<ColMajorMatrix> m(lhs, num_rows, num_cols);
+  qr_ = std::make_unique<QRType>(m);
+  *message = "Success.";
+  return LINEAR_SOLVER_SUCCESS;
+}
+
+LinearSolverTerminationType EigenDenseQR::Solve(const double* rhs,
+                                                double* solution,
+                                                std::string* message) {
+  VectorRef(solution, qr_->cols()) =
+      qr_->solve(ConstVectorRef(rhs, qr_->rows()));
+  *message = "Success.";
+  return LINEAR_SOLVER_SUCCESS;
+}
+
+#ifndef CERES_NO_LAPACK
+LinearSolverTerminationType LAPACKDenseQR::Factorize(int num_rows,
+                                                     int num_cols,
+                                                     double* lhs,
+                                                     std::string* message) {
+  int lwork = -1;
+  double work_size;
+  int info = 0;
+
+  // Compute the size of the temporary workspace needed to compute the QR
+  // factorization in the dgeqrf call below.
+  dgeqrf_(&num_rows,
+          &num_cols,
+          lhs_,
+          &num_rows,
+          tau_.data(),
+          &work_size,
+          &lwork,
+          &info);
+  if (info < 0) {
+    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
+               << "Please report it."
+               << "LAPACK::dgels fatal error."
+               << "Argument: " << -info << " is invalid.";
+  }
+
+  lhs_ = lhs;
+  num_rows_ = num_rows;
+  num_cols_ = num_cols;
+
+  lwork = static_cast<int>(work_size);
+
+  if (work_.size() < lwork) {
+    work_.resize(lwork);
+  }
+  if (tau_.size() < num_cols) {
+    tau_.resize(num_cols);
+  }
+
+  if (q_transpose_rhs_.size() < num_rows) {
+    q_transpose_rhs_.resize(num_rows);
+  }
+
+  // Factorize the lhs_ using the workspace that we just constructed above.
+  dgeqrf_(&num_rows,
+          &num_cols,
+          lhs_,
+          &num_rows,
+          tau_.data(),
+          work_.data(),
+          &lwork,
+          &info);
+
+  if (info < 0) {
+    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
+               << "Please report it. dgeqrf fatal error."
+               << "Argument: " << -info << " is invalid.";
+  }
+
+  termination_type_ = LINEAR_SOLVER_SUCCESS;
+  *message = "Success.";
+  return termination_type_;
+}
+
+LinearSolverTerminationType LAPACKDenseQR::Solve(const double* rhs,
+                                                 double* solution,
+                                                 std::string* message) {
+  if (termination_type_ != LINEAR_SOLVER_SUCCESS) {
+    *message = "QR factorization failed and solve called.";
+    return termination_type_;
+  }
+
+  std::copy_n(rhs, num_rows_, q_transpose_rhs_.data());
+
+  const char side = 'L';
+  char trans = 'T';
+  const int num_c_cols = 1;
+  const int lwork = work_.size();
+  int info = 0;
+  dormqr_(&side,
+          &trans,
+          &num_rows_,
+          &num_c_cols,
+          &num_cols_,
+          lhs_,
+          &num_rows_,
+          tau_.data(),
+          q_transpose_rhs_.data(),
+          &num_rows_,
+          work_.data(),
+          &lwork,
+          &info);
+  if (info < 0) {
+    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
+               << "Please report it. dormr fatal error."
+               << "Argument: " << -info << " is invalid.";
+  }
+
+  const char uplo = 'U';
+  trans = 'N';
+  const char diag = 'N';
+  dtrtrs_(&uplo,
+          &trans,
+          &diag,
+          &num_cols_,
+          &num_c_cols,
+          lhs_,
+          &num_rows_,
+          q_transpose_rhs_.data(),
+          &num_rows_,
+          &info);
+
+  if (info < 0) {
+    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
+               << "Please report it. dormr fatal error."
+               << "Argument: " << -info << " is invalid.";
+  } else if (info > 0) {
+    *message =
+        "QR factorization failure. The factorization is not full rank. R has "
+        "zeros on the diagonal.";
+    termination_type_ = LINEAR_SOLVER_FAILURE;
+  } else {
+    std::copy_n(q_transpose_rhs_.data(), num_cols_, solution);
+    termination_type_ = LINEAR_SOLVER_SUCCESS;
+  }
+
+  return termination_type_;
+}
+
+#endif  // CERES_NO_LAPACK
+
+}  // namespace internal
+}  // namespace ceres
diff --git a/internal/ceres/dense_qr.h b/internal/ceres/dense_qr.h
new file mode 100644
index 0000000..93d890b
--- /dev/null
+++ b/internal/ceres/dense_qr.h
@@ -0,0 +1,143 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2022 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)
+
+#ifndef CERES_INTERNAL_DENSE_QR_H_
+#define CERES_INTERNAL_DENSE_QR_H_
+
+// This include must come before any #ifndef check on Ceres compile options.
+// clang-format off
+#include "ceres/internal/port.h"
+// clang-format on
+
+#include <memory>
+#include <vector>
+
+#include "Eigen/Dense"
+#include "ceres/internal/eigen.h"
+#include "ceres/linear_solver.h"
+#include "glog/logging.h"
+
+namespace ceres {
+namespace internal {
+
+// An interface that abstracts away the internal details of various dense linear
+// algebra libraries and offers a simple API for solving dense linear systems
+// using a QR factorization.
+class CERES_EXPORT_INTERNAL DenseQR {
+ public:
+  static std::unique_ptr<DenseQR> Create(const LinearSolver::Options& options);
+
+  virtual ~DenseQR() = default;
+
+  // Computes the QR factorization of the given matrix.
+  //
+  // The input matrix lhs is assumed to be a column-major num_rows x num_cols
+  // matrix.
+  //
+  // The input matrix lhs may be modified by the implementation to store the
+  // factorization, irrespective of whether the factorization succeeds or not.
+  // As a result it is the user's responsibility to ensure that lhs is valid
+  // when Solve is called.
+  virtual LinearSolverTerminationType Factorize(int num_rows,
+                                                int num_cols,
+                                                double* lhs,
+                                                std::string* message) = 0;
+
+  // Computes the solution to the equation
+  //
+  // lhs * solution = rhs
+  //
+  // Calling Solve without calling Factorize is undefined behaviour. It is the
+  // user's responsibility to ensure that the input matrix lhs passed to
+  // Factorize has not been freed/modified when Solve is called.
+  virtual LinearSolverTerminationType Solve(const double* rhs,
+                                            double* solution,
+                                            std::string* message) = 0;
+
+  // Convenience method which combines a call to Factorize and Solve. Solve is
+  // only called if Factorize returns LINEAR_SOLVER_SUCCESS.
+  //
+  // The input matrix lhs may be modified by the implementation to store the
+  // factorization, irrespective of whether the method succeeds or not. It is
+  // the user's responsibility to ensure that lhs is valid if and when Solve is
+  // called again after this call.
+  LinearSolverTerminationType FactorAndSolve(int num_rows,
+                                             int num_cols,
+                                             double* lhs,
+                                             const double* rhs,
+                                             double* solution,
+                                             std::string* message);
+};
+
+class CERES_EXPORT_INTERNAL EigenDenseQR : public DenseQR {
+ public:
+  ~EigenDenseQR() override = default;
+
+  LinearSolverTerminationType Factorize(int num_rows,
+                                        int num_cols,
+                                        double* lhs,
+                                        std::string* message) override;
+  LinearSolverTerminationType Solve(const double* rhs,
+                                    double* solution,
+                                    std::string* message) override;
+
+ private:
+  using QRType = Eigen::HouseholderQR<Eigen::Ref<ColMajorMatrix>>;
+  std::unique_ptr<QRType> qr_;
+};
+
+#ifndef CERES_NO_LAPACK
+class CERES_EXPORT_INTERNAL LAPACKDenseQR : public DenseQR {
+ public:
+  ~LAPACKDenseQR() override = default;
+
+  LinearSolverTerminationType Factorize(int num_rows,
+                                        int num_cols,
+                                        double* lhs,
+                                        std::string* message) override;
+  LinearSolverTerminationType Solve(const double* rhs,
+                                    double* solution,
+                                    std::string* message) override;
+
+ private:
+  double* lhs_ = nullptr;
+  int num_rows_;
+  int num_cols_;
+  LinearSolverTerminationType termination_type_ = LINEAR_SOLVER_FATAL_ERROR;
+  Vector work_;
+  Vector tau_;
+  Vector q_transpose_rhs_;
+};
+#endif  // CERES_NO_LAPACK
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_INTERNAL_DENSE_QR_H_
diff --git a/internal/ceres/dense_qr_solver.cc b/internal/ceres/dense_qr_solver.cc
index 44388f3..24cb25a 100644
--- a/internal/ceres/dense_qr_solver.cc
+++ b/internal/ceres/dense_qr_solver.cc
@@ -33,9 +33,9 @@
 #include <cstddef>
 
 #include "Eigen/Dense"
+#include "ceres/dense_qr.h"
 #include "ceres/dense_sparse_matrix.h"
 #include "ceres/internal/eigen.h"
-#include "ceres/lapack.h"
 #include "ceres/linear_solver.h"
 #include "ceres/types.h"
 #include "ceres/wall_time.h"
@@ -44,124 +44,40 @@
 namespace internal {
 
 DenseQRSolver::DenseQRSolver(const LinearSolver::Options& options)
-    : options_(options) {
-  work_.resize(1);
-}
+    : options_(options), dense_qr_(DenseQR::Create(options)) {}
 
 LinearSolver::Summary DenseQRSolver::SolveImpl(
     DenseSparseMatrix* A,
     const double* b,
     const LinearSolver::PerSolveOptions& per_solve_options,
     double* x) {
-  if (options_.dense_linear_algebra_library_type == EIGEN) {
-    return SolveUsingEigen(A, b, per_solve_options, x);
-  } else {
-    return SolveUsingLAPACK(A, b, per_solve_options, x);
-  }
-}
-
-LinearSolver::Summary DenseQRSolver::SolveUsingLAPACK(
-    DenseSparseMatrix* A,
-    const double* b,
-    const LinearSolver::PerSolveOptions& per_solve_options,
-    double* x) {
   EventLogger event_logger("DenseQRSolver::Solve");
 
   const int num_rows = A->num_rows();
   const int num_cols = A->num_cols();
+  const int num_augmented_rows =
+      num_rows + ((per_solve_options.D != nullptr) ? num_cols : 0);
 
-  if (per_solve_options.D != NULL) {
-    // Temporarily append a diagonal block to the A matrix, but undo
-    // it before returning the matrix to the user.
-    A->AppendDiagonal(per_solve_options.D);
+  if (lhs_.rows() != num_augmented_rows || lhs_.cols() != num_cols) {
+    lhs_.resize(num_augmented_rows, num_cols);
+    rhs_.resize(num_augmented_rows);
   }
 
-  // TODO(sameeragarwal): Since we are copying anyways, the diagonal
-  // can be appended to the matrix instead of doing it on A.
-  lhs_ = A->matrix();
-
-  if (per_solve_options.D != NULL) {
-    // Undo the modifications to the matrix A.
-    A->RemoveDiagonal();
-  }
-
-  // rhs = [b;0] to account for the additional rows in the lhs.
-  if (rhs_.rows() != lhs_.rows()) {
-    rhs_.resize(lhs_.rows());
-  }
-  rhs_.setZero();
+  lhs_.topRows(num_rows) = A->matrix();
   rhs_.head(num_rows) = ConstVectorRef(b, num_rows);
 
-  if (work_.rows() == 1) {
-    const int work_size =
-        LAPACK::EstimateWorkSizeForQR(lhs_.rows(), lhs_.cols());
-    VLOG(3) << "Working memory for Dense QR factorization: "
-            << work_size * sizeof(double);
-    work_.resize(work_size);
+  if (num_rows != num_augmented_rows) {
+    lhs_.bottomRows(num_cols) =
+        ConstVectorRef(per_solve_options.D, num_cols).asDiagonal();
+    rhs_.tail(num_cols).setZero();
   }
 
   LinearSolver::Summary summary;
+  summary.termination_type = dense_qr_->FactorAndSolve(
+      lhs_.rows(), lhs_.cols(), lhs_.data(), rhs_.data(), x, &summary.message);
   summary.num_iterations = 1;
-  summary.termination_type = LAPACK::SolveInPlaceUsingQR(lhs_.rows(),
-                                                         lhs_.cols(),
-                                                         lhs_.data(),
-                                                         work_.rows(),
-                                                         work_.data(),
-                                                         rhs_.data(),
-                                                         &summary.message);
-  event_logger.AddEvent("Solve");
-  if (summary.termination_type == LINEAR_SOLVER_SUCCESS) {
-    VectorRef(x, num_cols) = rhs_.head(num_cols);
-  }
-
-  event_logger.AddEvent("TearDown");
-  return summary;
-}
-
-LinearSolver::Summary DenseQRSolver::SolveUsingEigen(
-    DenseSparseMatrix* A,
-    const double* b,
-    const LinearSolver::PerSolveOptions& per_solve_options,
-    double* x) {
-  EventLogger event_logger("DenseQRSolver::Solve");
-
-  const int num_rows = A->num_rows();
-  const int num_cols = A->num_cols();
-
-  if (per_solve_options.D != NULL) {
-    // Temporarily append a diagonal block to the A matrix, but undo
-    // it before returning the matrix to the user.
-    A->AppendDiagonal(per_solve_options.D);
-  }
-
-  // rhs = [b;0] to account for the additional rows in the lhs.
-  const int augmented_num_rows =
-      num_rows + ((per_solve_options.D != NULL) ? num_cols : 0);
-  if (rhs_.rows() != augmented_num_rows) {
-    rhs_.resize(augmented_num_rows);
-    rhs_.setZero();
-  }
-  rhs_.head(num_rows) = ConstVectorRef(b, num_rows);
-  event_logger.AddEvent("Setup");
-
-  // Solve the system.
-  VectorRef(x, num_cols) = A->matrix().householderQr().solve(rhs_);
   event_logger.AddEvent("Solve");
 
-  if (per_solve_options.D != NULL) {
-    // Undo the modifications to the matrix A.
-    A->RemoveDiagonal();
-  }
-
-  // We always succeed, since the QR solver returns the best solution
-  // it can. It is the job of the caller to determine if the solution
-  // is good enough or not.
-  LinearSolver::Summary summary;
-  summary.num_iterations = 1;
-  summary.termination_type = LINEAR_SOLVER_SUCCESS;
-  summary.message = "Success.";
-
-  event_logger.AddEvent("TearDown");
   return summary;
 }
 
diff --git a/internal/ceres/dense_qr_solver.h b/internal/ceres/dense_qr_solver.h
index 980243b..927dc32 100644
--- a/internal/ceres/dense_qr_solver.h
+++ b/internal/ceres/dense_qr_solver.h
@@ -32,6 +32,9 @@
 #ifndef CERES_INTERNAL_DENSE_QR_SOLVER_H_
 #define CERES_INTERNAL_DENSE_QR_SOLVER_H_
 
+#include <memory>
+
+#include "ceres/dense_qr.h"
 #include "ceres/internal/eigen.h"
 #include "ceres/internal/port.h"
 #include "ceres/linear_solver.h"
@@ -105,7 +108,7 @@
   const LinearSolver::Options options_;
   ColMajorMatrix lhs_;
   Vector rhs_;
-  Vector work_;
+  std::unique_ptr<DenseQR> dense_qr_;
 };
 
 }  // namespace internal
diff --git a/internal/ceres/dense_qr_test.cc b/internal/ceres/dense_qr_test.cc
new file mode 100644
index 0000000..c71f40e
--- /dev/null
+++ b/internal/ceres/dense_qr_test.cc
@@ -0,0 +1,114 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2022 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/dense_qr.h"
+
+#include <memory>
+#include <numeric>
+#include <string>
+#include <vector>
+
+#include "Eigen/Dense"
+#include "ceres/internal/eigen.h"
+#include "ceres/linear_solver.h"
+#include "glog/logging.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+typedef DenseLinearAlgebraLibraryType Param;
+
+std::string ParamInfoToString(testing::TestParamInfo<Param> info) {
+  return DenseLinearAlgebraLibraryTypeToString(info.param);
+}
+
+class DenseQRTest : public ::testing::TestWithParam<Param> {};
+
+TEST_P(DenseQRTest, FactorAndSolve) {
+  // TODO(sameeragarwal): Convert these tests into type parameterized tests so
+  // that we can test the single and double precision solvers.
+
+  using Scalar = double;
+  using MatrixType = Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>;
+  using VectorType = Eigen::Matrix<Scalar, Eigen::Dynamic, 1>;
+
+  LinearSolver::Options options;
+  options.dense_linear_algebra_library_type = GetParam();
+  std::unique_ptr<DenseQR> dense_qr = DenseQR::Create(options);
+
+  const int kNumTrials = 10;
+  const int kMinNumCols = 1;
+  const int kMaxNumCols = 10;
+  const int kMinRowsFactor = 1;
+  const int kMaxRowsFactor = 3;
+  for (int num_cols = kMinNumCols; num_cols < kMaxNumCols; ++num_cols) {
+    for (int num_rows = kMinRowsFactor * num_cols;
+         num_rows < kMaxRowsFactor * num_cols;
+         ++num_rows) {
+      for (int trial = 0; trial < kNumTrials; ++trial) {
+        MatrixType lhs = MatrixType::Random(num_rows, num_cols);
+        Vector x = VectorType::Random(num_cols);
+        Vector rhs = lhs * x;
+        Vector actual = Vector::Random(num_cols);
+
+        LinearSolver::Summary summary;
+        summary.termination_type = dense_qr->FactorAndSolve(num_rows,
+                                                            num_cols,
+                                                            lhs.data(),
+                                                            rhs.data(),
+                                                            actual.data(),
+                                                            &summary.message);
+        EXPECT_EQ(summary.termination_type, LINEAR_SOLVER_SUCCESS);
+        EXPECT_NEAR((x - actual).norm() / x.norm(),
+                    0.0,
+                    std::numeric_limits<double>::epsilon() * 100)
+            << "\nexpected: " << x.transpose()
+            << "\nactual  : " << actual.transpose();
+      }
+    }
+  }
+}
+
+#ifndef CERES_NO_LAPACK
+INSTANTIATE_TEST_SUITE_P(_,
+                         DenseQRTest,
+                         ::testing::Values(EIGEN, LAPACK),
+                         ParamInfoToString);
+#else
+INSTANTIATE_TEST_SUITE_P(_,
+                         DenseQRTest,
+                         ::testing::Values(EIGEN),
+                         ParamInfoToString);
+#endif
+
+}  // namespace internal
+}  // namespace ceres
diff --git a/internal/ceres/dense_sparse_matrix.cc b/internal/ceres/dense_sparse_matrix.cc
index 53207fe..80ea658 100644
--- a/internal/ceres/dense_sparse_matrix.cc
+++ b/internal/ceres/dense_sparse_matrix.cc
@@ -41,28 +41,10 @@
 namespace internal {
 
 DenseSparseMatrix::DenseSparseMatrix(int num_rows, int num_cols)
-    : has_diagonal_appended_(false), has_diagonal_reserved_(false) {
-  m_.resize(num_rows, num_cols);
-  m_.setZero();
-}
-
-DenseSparseMatrix::DenseSparseMatrix(int num_rows,
-                                     int num_cols,
-                                     bool reserve_diagonal)
-    : has_diagonal_appended_(false), has_diagonal_reserved_(reserve_diagonal) {
-  if (reserve_diagonal) {
-    // Allocate enough space for the diagonal.
-    m_.resize(num_rows + num_cols, num_cols);
-  } else {
-    m_.resize(num_rows, num_cols);
-  }
-  m_.setZero();
-}
+    : m_(Matrix(num_rows, num_cols)) {}
 
 DenseSparseMatrix::DenseSparseMatrix(const TripletSparseMatrix& m)
-    : m_(Eigen::MatrixXd::Zero(m.num_rows(), m.num_cols())),
-      has_diagonal_appended_(false),
-      has_diagonal_reserved_(false) {
+    : m_(Matrix::Zero(m.num_rows(), m.num_cols())) {
   const double* values = m.values();
   const int* rows = m.rows();
   const int* cols = m.cols();
@@ -73,8 +55,7 @@
   }
 }
 
-DenseSparseMatrix::DenseSparseMatrix(const ColMajorMatrix& m)
-    : m_(m), has_diagonal_appended_(false), has_diagonal_reserved_(false) {}
+DenseSparseMatrix::DenseSparseMatrix(const Matrix& m) : m_(m) {}
 
 void DenseSparseMatrix::SetZero() { m_.setZero(); }
 
@@ -96,72 +77,22 @@
 }
 
 void DenseSparseMatrix::ToDenseMatrix(Matrix* dense_matrix) const {
-  *dense_matrix = m_.block(0, 0, num_rows(), num_cols());
+  *dense_matrix = m_;
 }
 
-void DenseSparseMatrix::AppendDiagonal(double* d) {
-  CHECK(!has_diagonal_appended_);
-  if (!has_diagonal_reserved_) {
-    ColMajorMatrix tmp = m_;
-    m_.resize(m_.rows() + m_.cols(), m_.cols());
-    m_.setZero();
-    m_.block(0, 0, tmp.rows(), tmp.cols()) = tmp;
-    has_diagonal_reserved_ = true;
-  }
-
-  m_.bottomLeftCorner(m_.cols(), m_.cols()) =
-      ConstVectorRef(d, m_.cols()).asDiagonal();
-  has_diagonal_appended_ = true;
-}
-
-void DenseSparseMatrix::RemoveDiagonal() {
-  CHECK(has_diagonal_appended_);
-  has_diagonal_appended_ = false;
-  // Leave the diagonal reserved.
-}
-
-int DenseSparseMatrix::num_rows() const {
-  if (has_diagonal_reserved_ && !has_diagonal_appended_) {
-    return m_.rows() - m_.cols();
-  }
-  return m_.rows();
-}
+int DenseSparseMatrix::num_rows() const { return m_.rows(); }
 
 int DenseSparseMatrix::num_cols() const { return m_.cols(); }
 
-int DenseSparseMatrix::num_nonzeros() const {
-  if (has_diagonal_reserved_ && !has_diagonal_appended_) {
-    return (m_.rows() - m_.cols()) * m_.cols();
-  }
-  return m_.rows() * m_.cols();
-}
+int DenseSparseMatrix::num_nonzeros() const { return m_.rows() * m_.cols(); }
 
-ConstColMajorMatrixRef DenseSparseMatrix::matrix() const {
-  return ConstColMajorMatrixRef(
-      m_.data(),
-      ((has_diagonal_reserved_ && !has_diagonal_appended_)
-           ? m_.rows() - m_.cols()
-           : m_.rows()),
-      m_.cols(),
-      Eigen::Stride<Eigen::Dynamic, 1>(m_.rows(), 1));
-}
+const Matrix& DenseSparseMatrix::matrix() const { return m_; }
 
-ColMajorMatrixRef DenseSparseMatrix::mutable_matrix() {
-  return ColMajorMatrixRef(m_.data(),
-                           ((has_diagonal_reserved_ && !has_diagonal_appended_)
-                                ? m_.rows() - m_.cols()
-                                : m_.rows()),
-                           m_.cols(),
-                           Eigen::Stride<Eigen::Dynamic, 1>(m_.rows(), 1));
-}
+Matrix* DenseSparseMatrix::mutable_matrix() { return &m_; }
 
 void DenseSparseMatrix::ToTextFile(FILE* file) const {
   CHECK(file != nullptr);
-  const int active_rows = (has_diagonal_reserved_ && !has_diagonal_appended_)
-                              ? (m_.rows() - m_.cols())
-                              : m_.rows();
-
-  for (int r = 0; r < active_rows; ++r) {
+  for (int r = 0; r < m_.rows(); ++r) {
     for (int c = 0; c < m_.cols(); ++c) {
       fprintf(file, "% 10d % 10d %17f\n", r, c, m_(r, c));
     }
diff --git a/internal/ceres/dense_sparse_matrix.h b/internal/ceres/dense_sparse_matrix.h
index 94064b3..e2f4a6e 100644
--- a/internal/ceres/dense_sparse_matrix.h
+++ b/internal/ceres/dense_sparse_matrix.h
@@ -48,12 +48,10 @@
   // Build a matrix with the same content as the TripletSparseMatrix
   // m. This assumes that m does not have any repeated entries.
   explicit DenseSparseMatrix(const TripletSparseMatrix& m);
-  explicit DenseSparseMatrix(const ColMajorMatrix& m);
-
+  explicit DenseSparseMatrix(const Matrix& m);
   DenseSparseMatrix(int num_rows, int num_cols);
-  DenseSparseMatrix(int num_rows, int num_cols, bool reserve_diagonal);
 
-  virtual ~DenseSparseMatrix() {}
+  virtual ~DenseSparseMatrix() = default;
 
   // SparseMatrix interface.
   void SetZero() final;
@@ -69,37 +67,11 @@
   const double* values() const final { return m_.data(); }
   double* mutable_values() final { return m_.data(); }
 
-  ConstColMajorMatrixRef matrix() const;
-  ColMajorMatrixRef mutable_matrix();
-
-  // Only one diagonal can be appended at a time. The diagonal is appended to
-  // as a new set of rows, e.g.
-  //
-  // Original matrix:
-  //
-  //   x x x
-  //   x x x
-  //   x x x
-  //
-  // After append diagonal (1, 2, 3):
-  //
-  //   x x x
-  //   x x x
-  //   x x x
-  //   1 0 0
-  //   0 2 0
-  //   0 0 3
-  //
-  // Calling RemoveDiagonal removes the block. It is a fatal error to append a
-  // diagonal to a matrix that already has an appended diagonal, and it is also
-  // a fatal error to remove a diagonal from a matrix that has none.
-  void AppendDiagonal(double* d);
-  void RemoveDiagonal();
+  const Matrix& matrix() const;
+  Matrix* mutable_matrix();
 
  private:
-  ColMajorMatrix m_;
-  bool has_diagonal_appended_;
-  bool has_diagonal_reserved_;
+  Matrix m_;
 };
 
 }  // namespace internal
diff --git a/internal/ceres/lapack.cc b/internal/ceres/lapack.cc
deleted file mode 100644
index 7ce00a5..0000000
--- a/internal/ceres/lapack.cc
+++ /dev/null
@@ -1,132 +0,0 @@
-// 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: sameeragarwal@google.com (Sameer Agarwal)
-
-#include "ceres/lapack.h"
-
-#include "ceres/internal/port.h"
-#include "ceres/linear_solver.h"
-#include "glog/logging.h"
-
-#ifndef CERES_NO_LAPACK
-extern "C" void dgels_(char* uplo,
-                       int* m,
-                       int* n,
-                       int* nrhs,
-                       double* a,
-                       int* lda,
-                       double* b,
-                       int* ldb,
-                       double* work,
-                       int* lwork,
-                       int* info);
-#endif
-
-namespace ceres {
-namespace internal {
-
-int LAPACK::EstimateWorkSizeForQR(int num_rows, int num_cols) {
-#ifdef CERES_NO_LAPACK
-  LOG(FATAL) << "Ceres was built without a LAPACK library.";
-  return -1;
-#else
-  char trans = 'N';
-  int nrhs = 1;
-  int lwork = -1;
-  double work;
-  int info = 0;
-  dgels_(&trans,
-         &num_rows,
-         &num_cols,
-         &nrhs,
-         NULL,
-         &num_rows,
-         NULL,
-         &num_rows,
-         &work,
-         &lwork,
-         &info);
-
-  if (info < 0) {
-    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
-               << "Please report it."
-               << "LAPACK::dgels fatal error."
-               << "Argument: " << -info << " is invalid.";
-  }
-  return static_cast<int>(work);
-#endif
-}
-
-LinearSolverTerminationType LAPACK::SolveInPlaceUsingQR(
-    int num_rows,
-    int num_cols,
-    const double* in_lhs,
-    int work_size,
-    double* work,
-    double* rhs_and_solution,
-    std::string* message) {
-#ifdef CERES_NO_LAPACK
-  LOG(FATAL) << "Ceres was built without a LAPACK library.";
-  return LINEAR_SOLVER_FATAL_ERROR;
-#else
-  char trans = 'N';
-  int m = num_rows;
-  int n = num_cols;
-  int nrhs = 1;
-  int lda = num_rows;
-  int ldb = num_rows;
-  int info = 0;
-  double* lhs = const_cast<double*>(in_lhs);
-
-  dgels_(&trans,
-         &m,
-         &n,
-         &nrhs,
-         lhs,
-         &lda,
-         rhs_and_solution,
-         &ldb,
-         work,
-         &work_size,
-         &info);
-
-  if (info < 0) {
-    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
-               << "Please report it."
-               << "LAPACK::dgels fatal error."
-               << "Argument: " << -info << " is invalid.";
-  }
-
-  *message = "Success.";
-  return LINEAR_SOLVER_SUCCESS;
-#endif
-}
-
-}  // namespace internal
-}  // namespace ceres
diff --git a/internal/ceres/lapack.h b/internal/ceres/lapack.h
deleted file mode 100644
index 5c5bf8b..0000000
--- a/internal/ceres/lapack.h
+++ /dev/null
@@ -1,101 +0,0 @@
-// 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: sameeragarwal@google.com (Sameer Agarwal)
-
-#ifndef CERES_INTERNAL_LAPACK_H_
-#define CERES_INTERNAL_LAPACK_H_
-
-#include <string>
-
-#include "ceres/internal/port.h"
-#include "ceres/linear_solver.h"
-
-namespace ceres {
-namespace internal {
-
-class LAPACK {
- public:
-  // Solve
-  //
-  //  lhs * solution = rhs
-  //
-  // using a Cholesky factorization. Here
-  // lhs is a symmetric positive definite matrix. It is assumed to be
-  // column major and only the lower triangular part of the matrix is
-  // referenced.
-  //
-  // This function uses the LAPACK dpotrf and dpotrs routines.
-  //
-  // The return value and the message string together describe whether
-  // the solver terminated successfully or not and if so, what was the
-  // reason for failure.
-  static LinearSolverTerminationType SolveInPlaceUsingCholesky(
-      int num_rows,
-      const double* lhs,
-      double* rhs_and_solution,
-      std::string* message);
-
-  // The SolveUsingQR function requires a buffer for its temporary
-  // computation. This function given the size of the lhs matrix will
-  // return the size of the buffer needed.
-  static int EstimateWorkSizeForQR(int num_rows, int num_cols);
-
-  // Solve
-  //
-  //  lhs * solution = rhs
-  //
-  // using a dense QR factorization. lhs is an arbitrary (possibly
-  // rectangular) matrix with full column rank.
-  //
-  // work is an array of size work_size that this routine uses for its
-  // temporary storage. The optimal size of this array can be obtained
-  // by calling EstimateWorkSizeForQR.
-  //
-  // When calling, rhs_and_solution contains the rhs, and upon return
-  // the first num_col entries are the solution.
-  //
-  // This function uses the LAPACK dgels routine.
-  //
-  // The return value and the message string together describe whether
-  // the solver terminated successfully or not and if so, what was the
-  // reason for failure.
-  static LinearSolverTerminationType SolveInPlaceUsingQR(
-      int num_rows,
-      int num_cols,
-      const double* lhs,
-      int work_size,
-      double* work,
-      double* rhs_and_solution,
-      std::string* message);
-};
-
-}  // namespace internal
-}  // namespace ceres
-
-#endif  // CERES_INTERNAL_LAPACK_H_
diff --git a/internal/ceres/trust_region_minimizer_test.cc b/internal/ceres/trust_region_minimizer_test.cc
index cad30eb..8f544d6 100644
--- a/internal/ceres/trust_region_minimizer_test.cc
+++ b/internal/ceres/trust_region_minimizer_test.cc
@@ -131,7 +131,7 @@
       dense_jacobian = down_cast<DenseSparseMatrix*>(jacobian);
       dense_jacobian->SetZero();
 
-      ColMajorMatrixRef jacobian_matrix = dense_jacobian->mutable_matrix();
+      Matrix& jacobian_matrix = *(dense_jacobian->mutable_matrix());
       CHECK_EQ(jacobian_matrix.cols(), num_active_cols_);
 
       int column_index = 0;