on_effective_size_drop.hpp

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// Copyright 2024 Ekumen, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#ifndef BELUGA_POLICIES_ON_EFFECTIVE_SIZE_DROP_HPP
#define BELUGA_POLICIES_ON_EFFECTIVE_SIZE_DROP_HPP
 
#include <range/v3/range/concepts.hpp>
 
#include <beluga/algorithm/effective_sample_size.hpp>
#include <beluga/policies/policy.hpp>
 
namespace beluga::policies {
 
namespace detail {
 
struct on_effective_size_drop_policy {
  static constexpr double kDefaultThreshold = 0.5;
 
 
  template <class Range>
  constexpr bool operator()(Range&& range, double threshold = kDefaultThreshold) const {
    static_assert(ranges::sized_range<Range>);
    const auto size = static_cast<double>(ranges::size(range));
    return beluga::effective_sample_size(std::forward<Range>(range)) < size * threshold;
  }
 
  constexpr auto operator()(double threshold) const {
    return beluga::make_policy(ranges::bind_back(on_effective_size_drop_policy{}, threshold));
  }
};
 
}  // namespace detail
 
 
inline constexpr policy<detail::on_effective_size_drop_policy> on_effective_size_drop;
 
}  // namespace beluga::policies
 
#endif