accumulator.hpp

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#ifndef STAN_MATH_REV_FUN_ACCUMULATOR_HPP
#define STAN_MATH_REV_FUN_ACCUMULATOR_HPP
 
#include <stan/math/prim/fun/Eigen.hpp>
#include <stan/math/rev/meta.hpp>
#include <stan/math/rev/fun/sum.hpp>
#include <stan/math/prim/fun/accumulator.hpp>
#include <vector>
#include <type_traits>
 
namespace stan {
namespace math {
 
template <typename T>
class accumulator<T, require_var_t<T>> {
 private:
  static constexpr int max_size_ = 128;
  std::vector<var, arena_allocator<var>> buf_;
 
  void check_size() {
    if (buf_.size() == max_size_) {
      var tmp = stan::math::sum(buf_);
      buf_.resize(1);
      buf_[0] = tmp;
    }
  }
 
 public:
  accumulator() : buf_() { buf_.reserve(max_size_); }
 
  template <typename S, typename = require_stan_scalar_t<S>>
  inline void add(S x) {
    check_size();
    buf_.push_back(x);
  }
 
  template <typename S, require_matrix_t<S>* = nullptr>
  inline void add(const S& m) {
    check_size();
    buf_.push_back(stan::math::sum(m));
  }
 
  template <typename S, require_std_vector_vt<is_stan_scalar, S>* = nullptr>
  inline void add(const S& xs) {
    check_size();
    this->add(stan::math::sum(xs));
  }
 
  template <typename S,
            require_std_vector_vt<is_container_or_var_matrix, S>* = nullptr>
  inline void add(const S& xs) {
    check_size();
    for (const auto& i : xs) {
      this->add(i);
    }
  }
 
#ifdef STAN_OPENCL
  template <typename S,
            require_all_kernel_expressions_and_none_scalar_t<S>* = nullptr>
  inline void add(const var_value<S>& xs) {
    check_size();
    buf_.push_back(stan::math::sum(xs));
  }
 
  template <typename S,
            require_all_kernel_expressions_and_none_scalar_t<S>* = nullptr>
  inline void add(const S& xs) {
    check_size();
    buf_.push_back(stan::math::sum(xs));
  }
 
#endif
  inline var sum() const { return stan::math::sum(buf_); }
};
 
}  // namespace math
}  // namespace stan
 
#endif