Program Listing for File relative_constraint_impl.hpp

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#ifndef FUSE_CONSTRAINTS__RELATIVE_CONSTRAINT_IMPL_HPP_
#define FUSE_CONSTRAINTS__RELATIVE_CONSTRAINT_IMPL_HPP_

#include <Eigen/Dense>

#include <string>
#include <vector>

#include <fuse_constraints/normal_delta.hpp>
#include <fuse_constraints/normal_delta_orientation_2d.hpp>


namespace fuse_constraints
{

template<class Variable>
RelativeConstraint<Variable>::RelativeConstraint(
  const std::string & source,
  const Variable & variable1,
  const Variable & variable2,
  const fuse_core::VectorXd & delta,
  const fuse_core::MatrixXd & covariance)
: fuse_core::Constraint(source, {variable1.uuid(), variable2.uuid()}),  // NOLINT(whitespace/braces)
  delta_(delta),
  sqrt_information_(covariance.inverse().llt().matrixU())
{
  assert(variable1.size() == variable2.size());
  assert(delta.rows() == static_cast<int>(variable1.size()));
  assert(covariance.rows() == static_cast<int>(variable1.size()));
  assert(covariance.cols() == static_cast<int>(variable1.size()));
}

template<class Variable>
RelativeConstraint<Variable>::RelativeConstraint(
  const std::string & source,
  const Variable & variable1,
  const Variable & variable2,
  const fuse_core::VectorXd & partial_delta,
  const fuse_core::MatrixXd & partial_covariance,
  const std::vector<size_t> & indices)
: fuse_core::Constraint(source, {variable1.uuid(), variable2.uuid()})  // NOLINT(whitespace/braces)
{
  assert(variable1.size() == variable2.size());
  assert(partial_delta.rows() == static_cast<int>(indices.size()));
  assert(partial_covariance.rows() == static_cast<int>(indices.size()));
  assert(partial_covariance.cols() == static_cast<int>(indices.size()));
  // Compute the sqrt information of the provided cov matrix
  fuse_core::MatrixXd partial_sqrt_information = partial_covariance.inverse().llt().matrixU();
  // Assemble a mean vector and sqrt information matrix from the provided values, but in proper
  // Variable order
  //
  // What are we doing here?
  // The constraint equation is defined as: cost(x) = ||A * (x1 - x0 - b)||^2
  // If we are measuring a subset of dimensions, we only want to produce costs for
  // the measured dimensions. But the variable vectors will be full sized. We can make this all work
  // out by creating a non-square A matrix, where each row computes a cost for one measured
  // dimensions, and the columns are in the order defined by the variable.
  delta_ = fuse_core::VectorXd::Zero(variable1.size());
  sqrt_information_ = fuse_core::MatrixXd::Zero(indices.size(), variable1.size());
  for (size_t i = 0; i < indices.size(); ++i) {
    delta_(indices[i]) = partial_delta(i);
    sqrt_information_.col(indices[i]) = partial_sqrt_information.col(i);
  }
}

template<class Variable>
fuse_core::MatrixXd RelativeConstraint<Variable>::covariance() const
{
  // We want to compute:
  // cov = (sqrt_info' * sqrt_info)^-1
  // With some linear algebra, we can swap the transpose and the inverse.
  // cov = (sqrt_info^-1) * (sqrt_info^-1)'
  // But sqrt_info _may_ not be square. So we need to compute the pseudoinverse instead.
  // Eigen doesn't have a pseudoinverse function (for probably very legitimate reasons).
  // So we set the right hand side to identity, then solve using one of Eigen's many decompositions.
  auto I = fuse_core::MatrixXd::Identity(sqrt_information_.rows(), sqrt_information_.cols());
  fuse_core::MatrixXd pinv = sqrt_information_.colPivHouseholderQr().solve(I);
  return pinv * pinv.transpose();
}

template<class Variable>
void RelativeConstraint<Variable>::print(std::ostream & stream) const
{
  stream << type() << "\n"
         << "  source: " << source() << "\n"
         << "  uuid: " << uuid() << "\n"
         << "  variable1: " << variables().at(0) << "\n"
         << "  variable2: " << variables().at(1) << "\n"
         << "  delta: " << delta().transpose() << "\n"
         << "  sqrt_info: " << sqrtInformation() << "\n";

  if (loss()) {
    stream << "  loss: ";
    loss()->print(stream);
  }
}

template<class Variable>
ceres::CostFunction * RelativeConstraint<Variable>::costFunction() const
{
  // Create a Gaussian/Normal Delta constraint
  return new fuse_constraints::NormalDelta(sqrt_information_, delta_);
}

// Specialization for Orientation2D
template<>
inline ceres::CostFunction * RelativeConstraint<
  fuse_variables::Orientation2DStamped
>::costFunction()
const
{
  // Create a Gaussian/Normal Delta constraint
  return new NormalDeltaOrientation2D(sqrt_information_(0, 0), delta_(0));
}

// Specialize the type() method to return the name that is registered with the plugins
template<>
inline std::string RelativeConstraint<fuse_variables::AccelerationAngular2DStamped>::type() const
{
  return "fuse_constraints::RelativeAccelerationAngular2DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::AccelerationLinear2DStamped>::type() const
{
  return "fuse_constraints::RelativeAccelerationLinear2DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::Orientation2DStamped>::type() const
{
  return "fuse_constraints::RelativeOrientation2DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::Position2DStamped>::type() const
{
  return "fuse_constraints::RelativePosition2DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::Position3DStamped>::type() const
{
  return "fuse_constraints::RelativePosition3DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::VelocityAngular2DStamped>::type() const
{
  return "fuse_constraints::RelativeVelocityAngular2DStampedConstraint";
}

template<>
inline std::string RelativeConstraint<fuse_variables::VelocityLinear2DStamped>::type() const
{
  return "fuse_constraints::RelativeVelocityLinear2DStampedConstraint";
}

}  // namespace fuse_constraints

#endif  // FUSE_CONSTRAINTS__RELATIVE_CONSTRAINT_IMPL_HPP_