cuda_device.hpp

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/*
 * Copyright (c) 2021, NVIDIA CORPORATION.
 *
 * 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 <rmm/detail/error.hpp>
 
#include <cuda_runtime_api.h>
 
namespace rmm {
 
struct cuda_device_id {
  using value_type = int;  
 
  explicit constexpr cuda_device_id(value_type dev_id) noexcept : id_{dev_id} {}
 
  [[nodiscard]] constexpr value_type value() const noexcept { return id_; }
 
  // TODO re-add doxygen comment specifier /** for these hidden friend operators once this Breathe
  // bug is fixed: https://github.com/breathe-doc/breathe/issues/916
 
  [[nodiscard]] constexpr friend bool operator==(cuda_device_id const& lhs,
                                                 cuda_device_id const& rhs) noexcept
  {
    return lhs.value() == rhs.value();
  }
 
  [[nodiscard]] constexpr friend bool operator!=(cuda_device_id const& lhs,
                                                 cuda_device_id const& rhs) noexcept
  {
    return lhs.value() != rhs.value();
  }
 private:
  value_type id_;
};
 
inline cuda_device_id get_current_cuda_device()
{
  cuda_device_id::value_type dev_id{-1};
  RMM_ASSERT_CUDA_SUCCESS(cudaGetDevice(&dev_id));
  return cuda_device_id{dev_id};
}
 
inline int get_num_cuda_devices()
{
  cuda_device_id::value_type num_dev{-1};
  RMM_ASSERT_CUDA_SUCCESS(cudaGetDeviceCount(&num_dev));
  return num_dev;
}
 
struct cuda_set_device_raii {
  explicit cuda_set_device_raii(cuda_device_id dev_id)
    : old_device_{get_current_cuda_device()},
      needs_reset_{dev_id.value() >= 0 && old_device_ != dev_id}
  {
    if (needs_reset_) { RMM_ASSERT_CUDA_SUCCESS(cudaSetDevice(dev_id.value())); }
  }
  ~cuda_set_device_raii() noexcept
  {
    if (needs_reset_) { RMM_ASSERT_CUDA_SUCCESS(cudaSetDevice(old_device_.value())); }
  }
 
  cuda_set_device_raii(cuda_set_device_raii const&)            = delete;
  cuda_set_device_raii& operator=(cuda_set_device_raii const&) = delete;
  cuda_set_device_raii(cuda_set_device_raii&&)                 = delete;
  cuda_set_device_raii& operator=(cuda_set_device_raii&&)      = delete;
 
 private:
  cuda_device_id old_device_;
  bool needs_reset_;
};
  // end of group
}  // namespace rmm