text: #ifndef STAN_MATH_REV_CORE_SET_ZERO_ALL_ADJOINTS_NESTED_HPP
  #define STAN_MATH_REV_CORE_SET_ZERO_ALL_ADJOINTS_NESTED_HPP
  
  #include <stan/math/rev/core/vari.hpp>
  #include <stan/math/rev/core/chainable_alloc.hpp>
  #include <stan/math/rev/core/chainablestack.hpp>
  #include <stan/math/rev/core/empty_nested.hpp>
  #include <stdexcept>
  
  namespace stan {
  namespace math {
  
  /**
   * Reset all adjoint values in the top nested portion of the stack
   * to zero.
   */
  static void set_zero_all_adjoints_nested() {
    if (empty_nested()) {
      throw std::logic_error(
          "empty_nested() must be false before calling"
          " set_zero_all_adjoints_nested()");
    }
    size_t start1 = ChainableStack::instance_->nested_var_stack_sizes_.back();
    // avoid wrap with unsigned when start1 == 0
    for (size_t i = (start1 == 0U) ? 0U : (start1 - 1);
         i < ChainableStack::instance_->var_stack_.size(); ++i) {
      ChainableStack::instance_->var_stack_[i]->set_zero_adjoint();
    }
  
    size_t start2
        = ChainableStack::instance_->nested_var_nochain_stack_sizes_.back();
    for (size_t i = (start2 == 0U) ? 0U : (start2 - 1);
         i < ChainableStack::instance_->var_nochain_stack_.size(); ++i) {
      ChainableStack::instance_->var_nochain_stack_[i]->set_zero_adjoint();
    }
  }
  
  }  // namespace math
  }  // namespace stan
  #endif
  