complex_schur_decompose.hpp

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#ifndef STAN_MATH_PRIM_FUN_COMPLEX_SCHUR_DECOMPOSE_HPP
#define STAN_MATH_PRIM_FUN_COMPLEX_SCHUR_DECOMPOSE_HPP
 
#include <stan/math/prim/fun/Eigen.hpp>
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
 
namespace stan {
namespace math {
 
template <typename M, require_eigen_dense_dynamic_t<M>* = nullptr>
inline Eigen::Matrix<complex_return_t<scalar_type_t<M>>, -1, -1>
complex_schur_decompose_u(const M& m) {
  if (unlikely(m.size() == 0)) {
    return m;
  }
  check_square("complex_schur_decompose_u", "m", m);
  using MatType = Eigen::Matrix<scalar_type_t<M>, -1, -1>;
  // copy because ComplexSchur requires Eigen::Matrix type
  Eigen::ComplexSchur<MatType> cs{MatType(m)};
  return cs.matrixU();
}
 
template <typename M, require_eigen_dense_dynamic_t<M>* = nullptr>
inline Eigen::Matrix<complex_return_t<scalar_type_t<M>>, -1, -1>
complex_schur_decompose_t(const M& m) {
  if (unlikely(m.size() == 0)) {
    return m;
  }
  check_square("complex_schur_decompose_t", "m", m);
  using MatType = Eigen::Matrix<scalar_type_t<M>, -1, -1>;
  // copy because ComplexSchur requires Eigen::Matrix type
  Eigen::ComplexSchur<MatType> cs{MatType(m), false};
  return cs.matrixT();
}
 
template <typename M, require_eigen_dense_dynamic_t<M>* = nullptr>
inline std::tuple<Eigen::Matrix<complex_return_t<scalar_type_t<M>>, -1, -1>,
                  Eigen::Matrix<complex_return_t<scalar_type_t<M>>, -1, -1>>
complex_schur_decompose(const M& m) {
  if (unlikely(m.size() == 0)) {
    return std::make_tuple(m, m);
  }
  check_square("complex_schur_decompose", "m", m);
  using MatType = Eigen::Matrix<scalar_type_t<M>, -1, -1>;
  // copy because ComplexSchur requires Eigen::Matrix type
  Eigen::ComplexSchur<MatType> cs{MatType(m)};
  return std::make_tuple(std::move(cs.matrixU()), std::move(cs.matrixT()));
}
 
}  // namespace math
}  // namespace stan
#endif