mdivide_right.hpp

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#ifndef STAN_MATH_PRIM_FUN_MDIVIDE_RIGHT_HPP
#define STAN_MATH_PRIM_FUN_MDIVIDE_RIGHT_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/Eigen.hpp>
 
namespace stan {
namespace math {
 
template <typename EigMat1, typename EigMat2,
          require_all_eigen_t<EigMat1, EigMat2>* = nullptr,
          require_all_not_vt_fvar<EigMat1, EigMat2>* = nullptr>
inline Eigen::Matrix<return_type_t<EigMat1, EigMat2>,
                     EigMat1::RowsAtCompileTime, EigMat2::ColsAtCompileTime>
mdivide_right(const EigMat1& b, const EigMat2& A) {
  using T_return = return_type_t<EigMat1, EigMat2>;
  check_square("mdivide_right", "A", A);
  check_multiplicable("mdivide_right", "b", b, "A", A);
  if (A.size() == 0) {
    return {b.rows(), 0};
  }
 
  return Eigen::Matrix<T_return, EigMat2::RowsAtCompileTime,
                       EigMat2::ColsAtCompileTime>(A)
      .transpose()
      .lu()
      .solve(Eigen::Matrix<T_return, Eigen::Dynamic, Eigen::Dynamic>(b)
                 .transpose())
      .transpose();
}
 
}  // namespace math
}  // namespace stan
 
#endif