DPCT1012

Intel® DPC++ Compatibility Tool Developer Guide and Reference

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ID 768918

Date 7/13/2023

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Public

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DPCT1012

Message

Detected kernel execution time measurement pattern and generated an initial code for time measurements in SYCL. You can change the way time is measured depending on your goals.

Detailed Help

The generated code uses the CPU time to measure the kernel execution time. You can change the way time is measured depending on your requirements.

Suggestions to Fix

Review the logic and adjust it as needed.

For example, this original CUDA* code:

__global__ void kernel() {
  ...
}

void foo() {
  cudaEvent_t start;
  cudaEvent_t end;
  cudaEventCreate(&start);
  cudaEventCreate(&end);
  cudaEventRecord(start);
  kernel<<<1, 1>>>();
  cudaEventRecord(end, 0);
  cudaEventSynchronize(end);
  float time;
  cudaEventElapsedTime(&time, start, end);
}

results in the following migrated SYCL* code:

void kernel() {
  ...
}

void foo() {
  dpct::device_ext &dev_ct1 = dpct::get_current_device();
  sycl::queue &q_ct1 = dev_ct1.default_queue();
  dpct::event_ptr start;
  std::chrono::time_point<std::chrono::steady_clock> start_ct1;
  dpct::event_ptr end;
  std::chrono::time_point<std::chrono::steady_clock> end_ct1;
  start = new sycl::event();
  end = new sycl::event();
  /*
  DPCT1012:0: Detected kernel execution time measurement pattern and generated
  an initial code for time measurements in SYCL. You can change the way time is
  measured depending on your goals.
  */
  start_ct1 = std::chrono::steady_clock::now();
  *end = q_ct1.parallel_for(
      sycl::nd_range<3>(sycl::range<3>(1, 1, 1), sycl::range<3>(1, 1, 1)),
      [=](sycl::nd_item<3> item_ct1) {
        kernel();
      });
  /*
  DPCT1012:1: Detected kernel execution time measurement pattern and generated
  an initial code for time measurements in SYCL. You can change the way time is
  measured depending on your goals.
  */
  end->wait();
  end_ct1 = std::chrono::steady_clock::now();
  float time;
  time = std::chrono::duration<float, std::milli>(end_ct1 - start_ct1).count();
}

which is rewritten to:

// User can add `--enable-profiling` option to migrate the code
void kernel() {
  ...
}

void foo() {
  dpct::device_ext &dev_ct1 = dpct::get_current_device();
  sycl::queue &q_ct1 = dev_ct1.default_queue();
  dpct::event_ptr start;
  dpct::event_ptr end;
  start = new sycl::event();
  end = new sycl::event();
  *start = q_ct1.ext_oneapi_submit_barrier();
  q_ct1.parallel_for(
      sycl::nd_range<3>(sycl::range<3>(1, 1, 1), sycl::range<3>(1, 1, 1)),
      [=](sycl::nd_item<3> item_ct1) {
        kernel();
      });
  *end = q_ct1.ext_oneapi_submit_barrier();
  end->wait_and_throw();
  float time;
  time =
      (end->get_profiling_info<sycl::info::event_profiling::command_end>() -
       start
           ->get_profiling_info<sycl::info::event_profiling::command_start>()) /
      1000000.0f;
}

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Intel® DPC++ Compatibility Tool Developer Guide and Reference

DPCT1012

Message

Detailed Help

Suggestions to Fix