diff --git a/internal/ceres/problem.cc b/internal/ceres/problem.cc
new file mode 100644
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+++ b/internal/ceres/problem.cc
@@ -0,0 +1,203 @@
+// 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)
+//         keir@google.com (Keir Mierle)
+
+#include "ceres/problem.h"
+
+#include <vector>
+#include "ceres/crs_matrix.h"
+#include "ceres/problem_impl.h"
+
+namespace ceres {
+
+using std::vector;
+
+Problem::Problem() : problem_impl_(new internal::ProblemImpl) {}
+Problem::Problem(const Problem::Options& options)
+    : problem_impl_(new internal::ProblemImpl(options)) {}
+Problem::~Problem() {}
+
+ResidualBlockId Problem::AddResidualBlock(
+    CostFunction* cost_function,
+    LossFunction* loss_function,
+    const vector<double*>& parameter_blocks) {
+  return problem_impl_->AddResidualBlock(
+      cost_function,
+      loss_function,
+      parameter_blocks.data(),
+      static_cast<int>(parameter_blocks.size()));
+}
+
+ResidualBlockId Problem::AddResidualBlock(
+    CostFunction* cost_function,
+    LossFunction* loss_function,
+    double* const* const parameter_blocks,
+    int num_parameter_blocks) {
+  return problem_impl_->AddResidualBlock(cost_function,
+                                         loss_function,
+                                         parameter_blocks,
+                                         num_parameter_blocks);
+}
+
+void Problem::AddParameterBlock(double* values, int size) {
+  problem_impl_->AddParameterBlock(values, size);
+}
+
+void Problem::AddParameterBlock(double* values,
+                                int size,
+                                LocalParameterization* local_parameterization) {
+  problem_impl_->AddParameterBlock(values, size, local_parameterization);
+}
+
+void Problem::RemoveResidualBlock(ResidualBlockId residual_block) {
+  problem_impl_->RemoveResidualBlock(residual_block);
+}
+
+void Problem::RemoveParameterBlock(double* values) {
+  problem_impl_->RemoveParameterBlock(values);
+}
+
+void Problem::SetParameterBlockConstant(double* values) {
+  problem_impl_->SetParameterBlockConstant(values);
+}
+
+void Problem::SetParameterBlockVariable(double* values) {
+  problem_impl_->SetParameterBlockVariable(values);
+}
+
+bool Problem::IsParameterBlockConstant(double* values) const {
+  return problem_impl_->IsParameterBlockConstant(values);
+}
+
+void Problem::SetParameterization(
+    double* values,
+    LocalParameterization* local_parameterization) {
+  problem_impl_->SetParameterization(values, local_parameterization);
+}
+
+const LocalParameterization* Problem::GetParameterization(
+    double* values) const {
+  return problem_impl_->GetParameterization(values);
+}
+
+void Problem::SetParameterLowerBound(double* values,
+                                     int index,
+                                     double lower_bound) {
+  problem_impl_->SetParameterLowerBound(values, index, lower_bound);
+}
+
+void Problem::SetParameterUpperBound(double* values,
+                                     int index,
+                                     double upper_bound) {
+  problem_impl_->SetParameterUpperBound(values, index, upper_bound);
+}
+
+double Problem::GetParameterUpperBound(double* values, int index) const {
+  return problem_impl_->GetParameterUpperBound(values, index);
+}
+
+double Problem::GetParameterLowerBound(double* values, int index) const {
+  return problem_impl_->GetParameterLowerBound(values, index);
+}
+
+bool Problem::Evaluate(const EvaluateOptions& evaluate_options,
+                       double* cost,
+                       vector<double>* residuals,
+                       vector<double>* gradient,
+                       CRSMatrix* jacobian) {
+  return problem_impl_->Evaluate(evaluate_options,
+                                 cost,
+                                 residuals,
+                                 gradient,
+                                 jacobian);
+}
+
+int Problem::NumParameterBlocks() const {
+  return problem_impl_->NumParameterBlocks();
+}
+
+int Problem::NumParameters() const {
+  return problem_impl_->NumParameters();
+}
+
+int Problem::NumResidualBlocks() const {
+  return problem_impl_->NumResidualBlocks();
+}
+
+int Problem::NumResiduals() const {
+  return problem_impl_->NumResiduals();
+}
+
+int Problem::ParameterBlockSize(const double* parameter_block) const {
+  return problem_impl_->ParameterBlockSize(parameter_block);
+}
+
+int Problem::ParameterBlockLocalSize(const double* parameter_block) const {
+  return problem_impl_->ParameterBlockLocalSize(parameter_block);
+}
+
+bool Problem::HasParameterBlock(const double* values) const {
+  return problem_impl_->HasParameterBlock(values);
+}
+
+void Problem::GetParameterBlocks(vector<double*>* parameter_blocks) const {
+  problem_impl_->GetParameterBlocks(parameter_blocks);
+}
+
+void Problem::GetResidualBlocks(
+    vector<ResidualBlockId>* residual_blocks) const {
+  problem_impl_->GetResidualBlocks(residual_blocks);
+}
+
+void Problem::GetParameterBlocksForResidualBlock(
+    const ResidualBlockId residual_block,
+    vector<double*>* parameter_blocks) const {
+  problem_impl_->GetParameterBlocksForResidualBlock(residual_block,
+                                                    parameter_blocks);
+}
+
+const CostFunction* Problem::GetCostFunctionForResidualBlock(
+    const ResidualBlockId residual_block) const {
+  return problem_impl_->GetCostFunctionForResidualBlock(residual_block);
+}
+
+const LossFunction* Problem::GetLossFunctionForResidualBlock(
+    const ResidualBlockId residual_block) const {
+  return problem_impl_->GetLossFunctionForResidualBlock(residual_block);
+}
+
+void Problem::GetResidualBlocksForParameterBlock(
+    const double* values,
+    vector<ResidualBlockId>* residual_blocks) const {
+  problem_impl_->GetResidualBlocksForParameterBlock(values,
+                                                    residual_blocks);
+}
+
+}  // namespace ceres