DPCT1042

Intel® DPC++ Compatibility Tool Developer Guide and Reference

Download PDF

ID 768918

Date 7/13/2023

Version

Public

A newer version of this document is available. Customers should click here to go to the newest version.

Visible to Intel only — GUID: GUID-B338D863-5B3D-486E-9DC4-8CE065AAF68D

View Details

DPCT1042

Message

The size of the arguments passed to the SYCL kernel exceeds the minimum size limit (1024) for a non-custom SYCL device. You can get the hardware argument size limit by querying info::device::max_parameter_size. You may need to rewrite this code if the size of the arguments exceeds the hardware limit.

Detailed Help

The size of the arguments passed to the SYCL* kernel for non-custom SYCL device has a limit (see SYCL 1.2.1 standard, 4.6.4.2 Device information descriptors).

In cases where this warning occurs, you need to adjust the code manually to decrease the number of accessors or other arguments that are captured by the SYCL kernel lambda.

The following example shows how you can remove one accessor by merging two buffers with the same type.

For example, the following problem example code shows where the arguments captured by the SYCL kernel lambda exceed the size limit:

  ... // declarations for device0 to device30
  dpct::constant_memory<int, 1> device31(ARRAY_SIZE);
  dpct::constant_memory<int, 1> device32(ARRAY_SIZE);

  // kernel function declaration
  void kernel(sycl::nd_item<3> item_ct1, int *device0, ..., int *device32);

  void test_function() {
    ... // memcpy operations for device0 to device30
    dpct::dpct_memcpy(device31.get_ptr(), host, ARRAY_SIZE * sizeof(int));
    dpct::dpct_memcpy(device32.get_ptr(), host, ARRAY_SIZE * sizeof(int));
    {
      dpct::get_default_queue().submit([&](sycl::handler &cgh) {
        ... // accessors for device0 to device30, captured by SYCL kernel lambda
            auto device31_acc_ct1 = device31.get_access(cgh);
        auto device32_acc_ct1 = device32.get_access(cgh);
        cgh.parallel_for(sycl::nd_range<3>(sycl::range<3>(1), sycl::range<3>(1)),
                         [=](sycl::nd_item<3> item_ct1) {
                           kernel(item_ct1, ... /*arguments device0 to device30*/
                                            device31_acc_ct1.get_pointer(),
                                  device32_acc_ct1.get_pointer());
                         });
      });
    }
  }

The code is updated so that the two buffers (device31 and device32) of the same type are merged into one (device31), and the number of accessors is reduced by one:

  ... // declarations for device0 to device30
  dpct::constant_memory<int, 1> device32(ARRAY_SIZE + ARRAY_SIZE); // one buffer instead of two

  // kernel function declaration
  void kernel(sycl::nd_item<3> item_ct1, int *device0, ..., int *device32);

  void test_function() {
    ... // memcpy operations for device0 to device30
    dpct::dpct_memcpy(device31.get_ptr(), host, ARRAY_SIZE * sizeof(int));
    // memory copy with offset:
    dpct::dpct_memcpy(device31.get_ptr() + ARRAY_SIZE, host,
                      ARRAY_SIZE * sizeof(int));
    {
      dpct::get_default_queue().submit([&](sycl::handler &cgh) {
        ... // accessors for device0 to device30, captured by SYCL kernel lambda
            auto device31_acc_ct1 =
                device31.get_access(cgh); // only one accessor instead of 2
        cgh.parallel_for(sycl::nd_range<3>(sycl::range<3>(1), sycl::range<3>(1)),
                         [=](sycl::nd_item<3> item_ct1) {
                           // last parameter is modified to use offset and the
                           // same accessor as previous parameter
                           kernel(item_ct1, ... /*arguments device0 to device30*/
                                            device31_acc_ct1.get_pointer(),
                                  device31_acc_ct1.get_pointer() + ARRAY_SIZE);
                         });
      });
    }
  }

Suggestions to Fix

Review the code and adjust it.

Select Your Language

Using Intel.com Search

Quick Links

Recent Searches

Advanced Search

Only search in

Intel® DPC++ Compatibility Tool Developer Guide and Reference

DPCT1042

Message

Detailed Help

Suggestions to Fix