diff --git a/internal/ceres/residual_block.cc b/internal/ceres/residual_block.cc
new file mode 100644
index 0000000..7582e92
--- /dev/null
+++ b/internal/ceres/residual_block.cc
@@ -0,0 +1,217 @@
+// 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: keir@google.com (Keir Mierle)
+//         sameeragarwal@google.com (Sameer Agarwal)
+
+#include "ceres/residual_block.h"
+
+#include <algorithm>
+#include <cstddef>
+#include <vector>
+#include "ceres/corrector.h"
+#include "ceres/parameter_block.h"
+#include "ceres/residual_block_utils.h"
+#include "ceres/cost_function.h"
+#include "ceres/internal/eigen.h"
+#include "ceres/internal/fixed_array.h"
+#include "ceres/local_parameterization.h"
+#include "ceres/loss_function.h"
+#include "ceres/small_blas.h"
+
+using Eigen::Dynamic;
+
+namespace ceres {
+namespace internal {
+
+ResidualBlock::ResidualBlock(
+    const CostFunction* cost_function, const LossFunction* loss_function,
+    const std::vector<ParameterBlock*>& parameter_blocks, int index)
+    : cost_function_(cost_function),
+      loss_function_(loss_function),
+      parameter_blocks_(
+          new ParameterBlock*[cost_function->parameter_block_sizes().size()]),
+      index_(index) {
+  CHECK(cost_function_ != nullptr);
+  std::copy(parameter_blocks.begin(),
+            parameter_blocks.end(),
+            parameter_blocks_.get());
+}
+
+bool ResidualBlock::Evaluate(const bool apply_loss_function,
+                             double* cost,
+                             double* residuals,
+                             double** jacobians,
+                             double* scratch) const {
+  const int num_parameter_blocks = NumParameterBlocks();
+  const int num_residuals = cost_function_->num_residuals();
+
+  // Collect the parameters from their blocks. This will rarely allocate, since
+  // residuals taking more than 8 parameter block arguments are rare.
+  FixedArray<const double*, 8> parameters(num_parameter_blocks);
+  for (int i = 0; i < num_parameter_blocks; ++i) {
+    parameters[i] = parameter_blocks_[i]->state();
+  }
+
+  // Put pointers into the scratch space into global_jacobians as appropriate.
+  FixedArray<double*, 8> global_jacobians(num_parameter_blocks);
+  if (jacobians != NULL) {
+    for (int i = 0; i < num_parameter_blocks; ++i) {
+      const ParameterBlock* parameter_block = parameter_blocks_[i];
+      if (jacobians[i] != NULL &&
+          parameter_block->LocalParameterizationJacobian() != NULL) {
+        global_jacobians[i] = scratch;
+        scratch += num_residuals * parameter_block->Size();
+      } else {
+        global_jacobians[i] = jacobians[i];
+      }
+    }
+  }
+
+  // If the caller didn't request residuals, use the scratch space for them.
+  bool outputting_residuals = (residuals != NULL);
+  if (!outputting_residuals) {
+    residuals = scratch;
+  }
+
+  // Invalidate the evaluation buffers so that we can check them after
+  // the CostFunction::Evaluate call, to see if all the return values
+  // that were required were written to and that they are finite.
+  double** eval_jacobians = (jacobians != NULL) ? global_jacobians.get() : NULL;
+
+  InvalidateEvaluation(*this, cost, residuals, eval_jacobians);
+
+  if (!cost_function_->Evaluate(parameters.get(), residuals, eval_jacobians)) {
+    return false;
+  }
+
+  if (!IsEvaluationValid(*this,
+                         parameters.get(),
+                         cost,
+                         residuals,
+                         eval_jacobians)) {
+    std::string message =
+        "\n\n"
+        "Error in evaluating the ResidualBlock.\n\n"
+        "There are two possible reasons. Either the CostFunction did not evaluate and fill all    \n"  // NOLINT
+        "residual and jacobians that were requested or there was a non-finite value (nan/infinite)\n"  // NOLINT
+        "generated during the or jacobian computation. \n\n" +
+        EvaluationToString(*this,
+                           parameters.get(),
+                           cost,
+                           residuals,
+                           eval_jacobians);
+    LOG(WARNING) << message;
+    return false;
+  }
+
+  double squared_norm = VectorRef(residuals, num_residuals).squaredNorm();
+
+  // Update the jacobians with the local parameterizations.
+  if (jacobians != NULL) {
+    for (int i = 0; i < num_parameter_blocks; ++i) {
+      if (jacobians[i] != NULL) {
+        const ParameterBlock* parameter_block = parameter_blocks_[i];
+
+        // Apply local reparameterization to the jacobians.
+        if (parameter_block->LocalParameterizationJacobian() != NULL) {
+          // jacobians[i] = global_jacobians[i] * global_to_local_jacobian.
+          MatrixMatrixMultiply<Dynamic, Dynamic, Dynamic, Dynamic, 0>(
+              global_jacobians[i],
+              num_residuals,
+              parameter_block->Size(),
+              parameter_block->LocalParameterizationJacobian(),
+              parameter_block->Size(),
+              parameter_block->LocalSize(),
+              jacobians[i], 0, 0,  num_residuals, parameter_block->LocalSize());
+        }
+      }
+    }
+  }
+
+  if (loss_function_ == NULL || !apply_loss_function) {
+    *cost = 0.5 * squared_norm;
+    return true;
+  }
+
+  double rho[3];
+  loss_function_->Evaluate(squared_norm, rho);
+  *cost = 0.5 * rho[0];
+
+  // No jacobians and not outputting residuals? All done. Doing an early exit
+  // here avoids constructing the "Corrector" object below in a common case.
+  if (jacobians == NULL && !outputting_residuals) {
+    return true;
+  }
+
+  // Correct for the effects of the loss function. The jacobians need to be
+  // corrected before the residuals, since they use the uncorrected residuals.
+  Corrector correct(squared_norm, rho);
+  if (jacobians != NULL) {
+    for (int i = 0; i < num_parameter_blocks; ++i) {
+      if (jacobians[i] != NULL) {
+        const ParameterBlock* parameter_block = parameter_blocks_[i];
+
+        // Correct the jacobians for the loss function.
+        correct.CorrectJacobian(num_residuals,
+                                parameter_block->LocalSize(),
+                                residuals,
+                                jacobians[i]);
+      }
+    }
+  }
+
+  // Correct the residuals with the loss function.
+  if (outputting_residuals) {
+    correct.CorrectResiduals(num_residuals, residuals);
+  }
+  return true;
+}
+
+int ResidualBlock::NumScratchDoublesForEvaluate() const {
+  // Compute the amount of scratch space needed to store the full-sized
+  // jacobians. For parameters that have no local parameterization  no storage
+  // is needed and the passed-in jacobian array is used directly. Also include
+  // space to store the residuals, which is needed for cost-only evaluations.
+  // This is slightly pessimistic, since both won't be needed all the time, but
+  // the amount of excess should not cause problems for the caller.
+  int num_parameters = NumParameterBlocks();
+  int scratch_doubles = 1;
+  for (int i = 0; i < num_parameters; ++i) {
+    const ParameterBlock* parameter_block = parameter_blocks_[i];
+    if (!parameter_block->IsConstant() &&
+        parameter_block->LocalParameterizationJacobian() != NULL) {
+      scratch_doubles += parameter_block->Size();
+    }
+  }
+  scratch_doubles *= NumResiduals();
+  return scratch_doubles;
+}
+
+}  // namespace internal
+}  // namespace ceres