// Ceres Solver - A fast non-linear least squares minimizer
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// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/residual_block_utils.h"

#include <cmath>
#include <limits>
#include <memory>

#include "ceres/cost_function.h"
#include "ceres/parameter_block.h"
#include "ceres/residual_block.h"
#include "ceres/sized_cost_function.h"
#include "gtest/gtest.h"

namespace ceres {
namespace internal {

// Routine to check if ResidualBlock::Evaluate for unary CostFunction
// with one residual succeeds with true or dies.
static void CheckEvaluation(const CostFunction& cost_function, bool is_good) {
  double x = 1.0;
  ParameterBlock parameter_block(&x, 1, -1);
  std::vector<ParameterBlock*> parameter_blocks;
  parameter_blocks.push_back(&parameter_block);

  ResidualBlock residual_block(&cost_function, nullptr, parameter_blocks, -1);

  std::unique_ptr<double[]> scratch(
      new double[residual_block.NumScratchDoublesForEvaluate()]);

  double cost;
  double residuals;
  double jacobian;
  double* jacobians[] = {&jacobian};

  EXPECT_EQ(residual_block.Evaluate(
                true, &cost, &residuals, jacobians, scratch.get()),
            is_good);
}

// A CostFunction that behaves normally, i.e., it computes numerically
// valid residuals and jacobians.
class GoodCostFunction : public SizedCostFunction<1, 1> {
 public:
  bool Evaluate(double const* const* parameters,
                double* residuals,
                double** jacobians) const final {
    residuals[0] = 1;
    if (jacobians != nullptr && jacobians[0] != nullptr) {
      jacobians[0][0] = 0.0;
    }
    return true;
  }
};

// The following four CostFunctions simulate the different ways in
// which user code can cause ResidualBlock::Evaluate to fail.
class NoResidualUpdateCostFunction : public SizedCostFunction<1, 1> {
 public:
  bool Evaluate(double const* const* parameters,
                double* residuals,
                double** jacobians) const final {
    // Forget to update the residuals.
    // residuals[0] = 1;
    if (jacobians != nullptr && jacobians[0] != nullptr) {
      jacobians[0][0] = 0.0;
    }
    return true;
  }
};

class NoJacobianUpdateCostFunction : public SizedCostFunction<1, 1> {
 public:
  bool Evaluate(double const* const* parameters,
                double* residuals,
                double** jacobians) const final {
    residuals[0] = 1;
    if (jacobians != nullptr && jacobians[0] != nullptr) {
      // Forget to update the jacobians.
      // jacobians[0][0] = 0.0;
    }
    return true;
  }
};

class BadResidualCostFunction : public SizedCostFunction<1, 1> {
 public:
  bool Evaluate(double const* const* parameters,
                double* residuals,
                double** jacobians) const final {
    residuals[0] = std::numeric_limits<double>::infinity();
    if (jacobians != nullptr && jacobians[0] != nullptr) {
      jacobians[0][0] = 0.0;
    }
    return true;
  }
};

class BadJacobianCostFunction : public SizedCostFunction<1, 1> {
 public:
  bool Evaluate(double const* const* parameters,
                double* residuals,
                double** jacobians) const final {
    residuals[0] = 1.0;
    if (jacobians != nullptr && jacobians[0] != nullptr) {
      jacobians[0][0] = std::numeric_limits<double>::quiet_NaN();
    }
    return true;
  }
};

// Note: It is preferable to write the below test as:
//
//  CheckEvaluation(GoodCostFunction(), true);
//  CheckEvaluation(NoResidualUpdateCostFunction(), false);
//  CheckEvaluation(NoJacobianUpdateCostFunction(), false);
//  ...
//
// however, there is a bug in the version of GCC on Mac OS X we tested, which
// requires the objects get put into local variables instead of getting
// instantiated on the stack.
TEST(ResidualBlockUtils, CheckAllCombinationsOfBadness) {
  GoodCostFunction good_fun;
  CheckEvaluation(good_fun, true);
  NoResidualUpdateCostFunction no_residual;
  CheckEvaluation(no_residual, false);
  NoJacobianUpdateCostFunction no_jacobian;
  CheckEvaluation(no_jacobian, false);
  BadResidualCostFunction bad_residual;
  CheckEvaluation(bad_residual, false);
  BadJacobianCostFunction bad_jacobian;
  CheckEvaluation(bad_jacobian, false);
}

}  // namespace internal
}  // namespace ceres