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diff --git a/internal/ceres/cgnr_solver.cc b/internal/ceres/cgnr_solver.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2012 Google Inc. All rights reserved.
+// http://code.google.com/p/ceres-solver/
+//
+// 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: keir@google.com (Keir Mierle)
+
+#include "ceres/cgnr_solver.h"
+
+#include "glog/logging.h"
+#include "ceres/linear_solver.h"
+#include "ceres/cgnr_linear_operator.h"
+#include "ceres/conjugate_gradients_solver.h"
+#include "ceres/block_jacobi_preconditioner.h"
+
+namespace ceres {
+namespace internal {
+
+CgnrSolver::CgnrSolver(const LinearSolver::Options& options)
+  : options_(options),
+    jacobi_preconditioner_(NULL) {
+}
+
+LinearSolver::Summary CgnrSolver::Solve(
+    LinearOperator* A,
+    const double* b,
+    const LinearSolver::PerSolveOptions& per_solve_options,
+    double* x) {
+  // Form z = Atb.
+  scoped_array<double> z(new double[A->num_cols()]);
+  std::fill(z.get(), z.get() + A->num_cols(), 0.0);
+  A->LeftMultiply(b, z.get());
+
+  // Precondition if necessary.
+  LinearSolver::PerSolveOptions cg_per_solve_options = per_solve_options;
+  if (options_.preconditioner_type == JACOBI) {
+    if (jacobi_preconditioner_.get() == NULL) {
+      jacobi_preconditioner_.reset(new BlockJacobiPreconditioner(*A));
+    }
+    jacobi_preconditioner_->Update(*A, per_solve_options.D);
+    cg_per_solve_options.preconditioner = jacobi_preconditioner_.get();
+  } else if (options_.preconditioner_type != IDENTITY) {
+    LOG(FATAL) << "CGNR only supports IDENTITY and JACOBI preconditioners.";
+  }
+
+  // Solve (AtA + DtD)x = z (= Atb).
+  std::fill(x, x + A->num_cols(), 0.0);
+  CgnrLinearOperator lhs(*A, per_solve_options.D);
+  ConjugateGradientsSolver conjugate_gradient_solver(options_);
+  return conjugate_gradient_solver.Solve(&lhs,
+                                         z.get(),
+                                         cg_per_solve_options,
+                                         x);
+}
+
+}  // namespace internal
+}  // namespace ceres