text: // Copyright (C) 2019-2020 Zilliz. All rights reserved.
  //
  // 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
  
  #pragma once
  
  #include <memory>
  #include <vector>
  
  #include "knowhere/common/Exception.h"
  #include "knowhere/common/Log.h"
  #include "knowhere/index/vector_index/VecIndex.h"
  
  namespace milvus {
  namespace knowhere {
  
  namespace impl {
  class NsgIndex;
  }
  
  class NSG : public VecIndex {
   public:
      explicit NSG(const int64_t gpu_num = -1) : gpu_(gpu_num) {
          if (gpu_ >= 0) {
              index_mode_ = IndexMode::MODE_GPU;
          }
          index_type_ = IndexEnum::INDEX_NSG;
      }
  
      BinarySet
      Serialize(const Config& config = Config()) override;
  
      void
      Load(const BinarySet&) override;
  
      void
      BuildAll(const DatasetPtr&, const Config&) override;
  
      void
      Train(const DatasetPtr&, const Config&) override {
          KNOWHERE_THROW_MSG("NSG not support build item dynamically, please invoke BuildAll interface.");
      }
  
      void
      AddWithoutIds(const DatasetPtr&, const Config&) override {
          KNOWHERE_THROW_MSG("Incremental index NSG is not supported");
      }
  
      DatasetPtr
      Query(const DatasetPtr&, const Config&) override;
  
      int64_t
      Count() override;
  
      int64_t
      Dim() override;
  
      void
      UpdateIndexSize() override;
  
   private:
      int64_t gpu_;
      std::shared_ptr<impl::NsgIndex> index_;
  };
  
  using NSGIndexPtr = std::shared_ptr<NSG>();
  
  }  // namespace knowhere
  }  // namespace milvus
  