gain_recovery.hpp

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/*
 * Copyright © 2025-2026 Akreon LLC
 * SPDX-License-Identifier: Apache-2.0
 */
 
#pragma once
 
#include "akreon/linalg/operator/matrix_inverse.hpp"
 
namespace control {
 
template <linalg::SquareMatrix PMat, linalg::MatrixContainer YMat>
constexpr auto recover_state_feedback_gain(const PMat& P, const YMat& Y) {
  using T = linalg::matrix_scalar_t<PMat>;
  static constexpr std::size_t InputDim = linalg::mat_rows_v<YMat>;
  static constexpr std::size_t StateDim = linalg::mat_cols_v<YMat>;
  static_assert(linalg::mat_rows_v<PMat> == StateDim,
                "P row dimension must match Y column dimension");
  static_assert(linalg::mat_cols_v<PMat> == StateDim,
                "P column dimension must match Y column dimension");
 
  using KMat = linalg::Matrix<T, InputDim, StateDim>;
  const auto [P_inv, event] = linalg::SymmetricMatrixInverse<PMat>()(P);
  if (event != linalg::NumericalEvent::NONE) return std::tuple(KMat{}, event);
  const auto K = Y * P_inv;
  return std::tuple(K, linalg::NumericalEvent::NONE);
}
 
template <linalg::SquareMatrix QMat, linalg::MatrixContainer WMat>
constexpr auto recover_state_observer_gain(const QMat& Q, const WMat& W) {
  using T = linalg::matrix_scalar_t<QMat>;
  static constexpr std::size_t StateDim = linalg::mat_rows_v<WMat>;
  static constexpr std::size_t MeasurementDim = linalg::mat_cols_v<WMat>;
  static_assert(linalg::mat_rows_v<QMat> == StateDim,
                "Q row dimension must match W row dimension");
  static_assert(linalg::mat_cols_v<QMat> == StateDim,
                "Q column dimension must match W row dimension");
 
  using LMat = linalg::Matrix<T, StateDim, MeasurementDim>;
  const auto [Q_inv, event] = linalg::SymmetricMatrixInverse<QMat>()(Q);
  if (event != linalg::NumericalEvent::NONE) return std::tuple(LMat{}, event);
  const auto L = Q_inv * W;
  return std::tuple(L, linalg::NumericalEvent::NONE);
}
 
} // namespace control