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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: strandmark@google.com (Petter Strandmark)
+//
+// Class for loading the data required for descibing a Fields of Experts (FoE)
+// model.
+
+#include "fields_of_experts.h"
+
+#include <fstream>
+#include <cmath>
+
+#include "pgm_image.h"
+
+namespace ceres {
+namespace examples {
+
+FieldsOfExpertsCost::FieldsOfExpertsCost(const std::vector<double>& filter)
+    : filter_(filter) {
+  set_num_residuals(1);
+  for (int i = 0; i < filter_.size(); ++i) {
+    mutable_parameter_block_sizes()->push_back(1);
+  }
+}
+
+// This is a dot product between a the scalar parameters and a vector of filter
+// coefficients.
+bool FieldsOfExpertsCost::Evaluate(double const* const* parameters,
+                                   double* residuals,
+                                   double** jacobians) const {
+  int num_variables = filter_.size();
+  residuals[0] = 0;
+  for (int i = 0; i < num_variables; ++i) {
+    residuals[0] += filter_[i] * parameters[i][0];
+  }
+
+  if (jacobians != NULL) {
+    for (int i = 0; i < num_variables; ++i) {
+      if (jacobians[i] != NULL) {
+        jacobians[i][0] = filter_[i];
+      }
+    }
+  }
+
+  return true;
+}
+
+// This loss function builds the FoE terms and is equal to
+//
+//   f(x) = alpha_i * log(1 + (1/2)s)
+//
+void FieldsOfExpertsLoss::Evaluate(double sq_norm, double rho[3]) const {
+  const double c = 0.5;
+  const double sum = 1.0 + sq_norm * c;
+  const double inv = 1.0 / sum;
+  // 'sum' and 'inv' are always positive, assuming that 's' is.
+  rho[0] = alpha_ *  log(sum);
+  rho[1] = alpha_ * c * inv;
+  rho[2] = - alpha_ * c * c * inv * inv;
+}
+
+FieldsOfExperts::FieldsOfExperts()
+    :  size_(0), num_filters_(0) {
+}
+
+bool FieldsOfExperts::LoadFromFile(const std::string& filename) {
+  std::ifstream foe_file(filename.c_str());
+  foe_file >> size_;
+  foe_file >> num_filters_;
+  if (size_ < 0 || num_filters_ < 0) {
+    return false;
+  }
+  const int num_variables = NumVariables();
+
+  x_delta_indices_.resize(num_variables);
+  for (int i = 0; i < num_variables; ++i) {
+    foe_file >> x_delta_indices_[i];
+  }
+
+  y_delta_indices_.resize(NumVariables());
+  for (int i = 0; i < num_variables; ++i) {
+    foe_file >> y_delta_indices_[i];
+  }
+
+  alpha_.resize(num_filters_);
+  for (int i = 0; i < num_filters_; ++i) {
+    foe_file >> alpha_[i];
+  }
+
+  filters_.resize(num_filters_);
+  for (int i = 0; i < num_filters_; ++i) {
+    filters_[i].resize(num_variables);
+    for (int j = 0; j < num_variables; ++j) {
+      foe_file >> filters_[i][j];
+    }
+  }
+
+  // If any read failed, return failure.
+  if (!foe_file) {
+    size_ = 0;
+    return false;
+  }
+
+  // There cannot be anything else in the file. Try reading another number and
+  // return failure if that succeeded.
+  double temp;
+  foe_file >> temp;
+  if (foe_file) {
+    size_ = 0;
+    return false;
+  }
+
+  return true;
+}
+
+ceres::CostFunction* FieldsOfExperts::NewCostFunction(int alpha_index) const {
+  return new FieldsOfExpertsCost(filters_[alpha_index]);
+}
+
+ceres::LossFunction* FieldsOfExperts::NewLossFunction(int alpha_index) const {
+  return new FieldsOfExpertsLoss(alpha_[alpha_index]);
+}
+
+
+}  // namespace examples
+}  // namespace ceres