tcrossprod.hpp

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#ifndef STAN_MATH_FWD_FUN_TCROSSPROD_HPP
#define STAN_MATH_FWD_FUN_TCROSSPROD_HPP
 
#include <stan/math/prim/fun/Eigen.hpp>
#include <stan/math/fwd/meta.hpp>
#include <stan/math/fwd/fun/multiply.hpp>
#include <stan/math/prim/fun/to_ref.hpp>
#include <stan/math/prim/fun/transpose.hpp>
 
namespace stan {
namespace math {
 
template <typename EigMat, require_eigen_vt<is_fvar, EigMat>* = nullptr>
inline Eigen::Matrix<value_type_t<EigMat>, EigMat::RowsAtCompileTime,
                     EigMat::RowsAtCompileTime>
tcrossprod(const EigMat& m) {
  if (m.rows() == 0) {
    return {};
  }
  const auto& m_ref = to_ref(m);
  auto ret = multiply(m_ref, m_ref.transpose());
  if constexpr (is_stan_scalar<decltype(ret)>::value) {
    return Eigen::Matrix<value_type_t<EigMat>, EigMat::RowsAtCompileTime,
                         EigMat::RowsAtCompileTime>{{ret}};
  } else {
    return ret;
  }
}
 
}  // namespace math
}  // namespace stan
#endif