flash-attention/csrc/cutlass/tools/profiler/src/gpu_timer.cpp

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/* \file
   \brief Defines a math function
*/

#include <stdexcept>

#include "cutlass/profiler/gpu_timer.h"

namespace cutlass {
namespace profiler {

/////////////////////////////////////////////////////////////////////////////////////////////////

GpuTimer::GpuTimer() {
  cudaError_t result;

  for (auto & event : events) {
    result = cudaEventCreate(&event);
    if (result != cudaSuccess) {
      throw std::runtime_error("Failed to create CUDA event");
    }
  }
}

GpuTimer::~GpuTimer() {
  for (auto & event : events) {
    cudaEventDestroy(event);
  }
}

/// Records a start event in the stream
void GpuTimer::start(cudaStream_t stream) {
  cudaError_t result = cudaEventRecord(events[0], stream);
  if (result != cudaSuccess) {
    throw std::runtime_error("Failed to record start event.");
  }
}

/// Records a stop event in the stream
void GpuTimer::stop(cudaStream_t stream) {
cudaError_t result = cudaEventRecord(events[1], stream);
  if (result != cudaSuccess) {
    throw std::runtime_error("Failed to record stop event.");
  }
}

/// Records a stop event in the stream and synchronizes on the stream
void GpuTimer::stop_and_wait(cudaStream_t stream) {

  stop(stream);

  cudaError_t result;
  if (stream) {
    result = cudaStreamSynchronize(stream);
    if (result != cudaSuccess) {
      throw std::runtime_error("Failed to synchronize with non-null CUDA stream.");
    }
  }
  else {
    result = cudaDeviceSynchronize();
    if (result != cudaSuccess) {
      throw std::runtime_error("Failed to synchronize with CUDA device.");
    }
  }
}

/// Returns the duration in milliseconds
double GpuTimer::duration(int iterations) const {

  float avg_ms;

  cudaError_t result = cudaEventElapsedTime(&avg_ms, events[0], events[1]);
  if (result != cudaSuccess) {
    throw std::runtime_error("Failed to query elapsed time from CUDA events.");
  }

  return double(avg_ms) / double(iterations);
}

/////////////////////////////////////////////////////////////////////////////////////////////////

} // namespace profiler
} // namespace cutlass