dot_product.hpp

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#ifndef STAN_MATH_PRIM_FUN_DOT_PRODUCT_HPP
#define STAN_MATH_PRIM_FUN_DOT_PRODUCT_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/Eigen.hpp>
#include <vector>
 
namespace stan {
namespace math {
 
template <typename Vec1, typename Vec2,
          require_all_eigen_vector_t<Vec1, Vec2>* = nullptr,
          require_not_var_t<return_type_t<Vec1, Vec2>>* = nullptr>
inline auto dot_product(Vec1&& v1, Vec2&& v2) {
  check_matching_sizes("dot_product", "v1", v1, "v2", v2);
  return make_holder(
      [](auto&& v1_, auto&& v2_) {
        return std::forward<decltype(v1_)>(v1_).dot(
            std::forward<decltype(v2_)>(v2_));
      },
      std::forward<Vec1>(v1), std::forward<Vec2>(v2));
}
 
template <typename Scalar1, typename Scalar2,
          require_all_stan_scalar_t<Scalar1, Scalar2>* = nullptr,
          require_all_not_var_t<Scalar1, Scalar2>* = nullptr>
inline auto dot_product(const Scalar1* v1, const Scalar2* v2, size_t length) {
  return_type_t<Scalar1, Scalar2> result = 0;
  for (size_t i = 0; i < length; i++) {
    result += v1[i] * v2[i];
  }
  return result;
}
 
template <typename Scalar1, typename Scalar2, typename Alloc1, typename Alloc2,
          require_all_stan_scalar_t<Scalar1, Scalar2>* = nullptr>
inline return_type_t<Scalar1, Scalar2> dot_product(
    const std::vector<Scalar1, Alloc1>& v1,
    const std::vector<Scalar2, Alloc2>& v2) {
  check_matching_sizes("dot_product", "v1", v1, "v2", v2);
 
  if (v1.size() == 0) {
    return 0.0;
  }
 
  return dot_product(as_column_vector_or_scalar(v1),
                     as_column_vector_or_scalar(v2));
}
 
}  // namespace math
}  // namespace stan
 
#endif