project_6/cccl_upstream/thrust/examples/include/timer.h

// SPDX-FileCopyrightText: Copyright (c) 2008-2009, NVIDIA Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

#pragma once

// A simple timer class

#ifdef __CUDACC__

// use CUDA's high-resolution timers when possible
#  include <thrust/system/cuda/error.h>
#  include <thrust/system_error.h>

#  include <string>

#  include <cuda_runtime_api.h>

void cuda_safe_call(cudaError_t error, const std::string& message = "")
{
  if (error)
  {
    throw thrust::system_error(error, thrust::cuda_category(), message);
  }
}

struct timer
{
  cudaEvent_t start;
  cudaEvent_t end;

  timer()
  {
    cuda_safe_call(cudaEventCreate(&start));
    cuda_safe_call(cudaEventCreate(&end));
    restart();
  }

  ~timer()
  {
    static_cast<void>(cudaEventDestroy(start));
    static_cast<void>(cudaEventDestroy(end));
  }

  void restart()
  {
    cuda_safe_call(cudaEventRecord(start, nullptr));
  }

  double elapsed()
  {
    cuda_safe_call(cudaEventRecord(end, nullptr));
    cuda_safe_call(cudaEventSynchronize(end));

    float ms_elapsed;
    cuda_safe_call(cudaEventElapsedTime(&ms_elapsed, start, end));
    return ms_elapsed / 1e3;
  }

  double epsilon()
  {
    return 0.5e-6;
  }
};

#else

// fallback to clock()
#  include <ctime>

struct timer
{
  clock_t start;
  clock_t end;

  timer()
  {
    restart();
  }

  ~timer() = default;

  void restart()
  {
    start = clock();
  }

  double elapsed()
  {
    end = clock();

    return static_cast<double>(end - start) / static_cast<double>(CLOCKS_PER_SEC);
  }

  double epsilon()
  {
    return 1.0 / static_cast<double>(CLOCKS_PER_SEC);
  }
};

#endif