include/tenzr/modules/checkpoint/checkpoint_manager.h¶

// Copyright 2026 The Tenzr Project Authors
//
// SPDX-License-Identifier: Apache-2.0
//
// 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
//
//      https://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 TENZR_MODULES_CHECKPOINT_CHECKPOINT_MANAGER_H_
#define TENZR_MODULES_CHECKPOINT_CHECKPOINT_MANAGER_H_

#include <cstdint>
#include <future>
#include <memory>
#include <optional>
#include <string>
#include <unordered_map>
#include <vector>

#include "tenzr/frontend/tensor.h"
#include "tenzr/modules/nn/module.h"

namespace tenzr::checkpoint {

  struct CheckpointOptions {
    std::string directory{"checkpoints"};
    size_t max_to_keep{3};
    bool keep_best{true};
    bool higher_is_better{false};
    std::string prefix{"step_"};
    bool async{false};
  };

  struct CheckpointMetadata {
    uint64_t step{0};
    std::string path;
    double metric{0.0};
    bool has_metric{false};
    uint64_t timestamp{0};
  };

  class CheckpointManager {
   public:
    explicit CheckpointManager(CheckpointOptions options = {});
    ~CheckpointManager();

    CheckpointManager(const CheckpointManager&) = delete;
    CheckpointManager& operator=(const CheckpointManager&) = delete;
    CheckpointManager(CheckpointManager&&) noexcept;
    CheckpointManager& operator=(CheckpointManager&&) noexcept;

    void Save(uint64_t step, const std::unordered_map<std::string, Tensor>& state, std::optional<double> metric = std::nullopt);
    void Save(uint64_t step, nn::Module& module, std::optional<double> metric = std::nullopt);

    std::unordered_map<std::string, Tensor> Restore(uint64_t step);
    std::unordered_map<std::string, Tensor> RestoreLatest();
    std::unordered_map<std::string, Tensor> RestoreBest();

    void Restore(uint64_t step, nn::Module& module);
    void RestoreLatest(nn::Module& module);
    void RestoreBest(nn::Module& module);

    bool HasCheckpoints() const;
    uint64_t LatestStep() const;
    uint64_t BestStep() const;
    std::vector<uint64_t> AllSteps() const;

    void WaitUntilIdle();

    const CheckpointOptions& Options() const { return options_; }

   private:
    void SaveInternal(uint64_t step, std::unordered_map<std::string, Tensor> state, std::optional<double> metric);
    void ApplyRetentionPolicy();
    void ScanExistingCheckpoints();

    CheckpointOptions options_;
    std::vector<CheckpointMetadata> checkpoints_;
    std::optional<uint64_t> best_step_;
    double best_metric_{0.0};
    std::vector<std::future<void>> pending_tasks_;
  };

}  // namespace tenzr::checkpoint

#endif  // TENZR_MODULES_CHECKPOINT_CHECKPOINT_MANAGER_H_