oneDAL dbscan sample code exception

[AlexZhao-becls]

oneDAL dbscan sample code exception

Build and run oneDAL/examples/oneapi/cpp/source/dbscan/dbscan_brute_force_batch.cpp.
Exception occurs when to call
const auto result_compute = dal::compute(q, dbscan_desc, x_data);

Debugger stops in Line 65 of compute_ops.hpp as below:

    template <typename Context>
    auto operator()(const Context& ctx, const Descriptor& desc, const input_t& input) const {
        check_preconditions(desc, input);
        const auto result =   // line 65
           compute_ops_dispatcher<Context, float_t, method_t, task_t>()(ctx, desc, input);
        check_postconditions(desc, input, result);
       return result;
    }

Exception thrown at 0x0000000000000000 in TestDBSCAN.exe: 0xC0000005: Access violation executing location 0x0000000000000000.

The sycl::queue q is built on CPU - Intel(R) OpenCL, 12th Gen Intel(R) Core(TM) i7-1260P
OS: Windows 10 Enterprise 22H2
oneAPI: 2025.0
Visual Studio 2022 64-bit Version 17.7.5

Try to remove the explicit "q" param as below:
const auto result_compute = dal::compute(dbscan_desc, x_data);
there is no exception.

[Alexandr-Solovev]

Hi, @AlexZhao-becls !
Have you used modified version of the oneDAL/examples/oneapi/cpp/source/dbscan/dbscan_brute_force_batch.cpp file, because we dont use q in this example
https://github.com/uxlfoundation/oneDAL/blob/main/examples/oneapi/cpp/source/dbscan/dbscan_brute_force_batch.cpp#L27
If you want to use sycl::queue it makes to take a look on our dpc examples:
https://github.com/uxlfoundation/oneDAL/blob/main/examples/oneapi/dpc/source/dbscan/dbscan_brute_force_batch.cpp#L35

[AlexZhao-becls]

Hi, @Alexandr-Solovev,

Thanks for your response. I want to use sycl::queue in my investigation to evaluate the performance on different devices.
I tried the dpc example: https://github.com/uxlfoundation/oneDAL/blob/main/examples/oneapi/dpc/source/dbscan/dbscan_brute_force_batch.cpp#L35
And, the exception occurs on CPU as what I described in this issue. There is no exception for this example on second device of "Intel(R) Iris(R) Xe Graphics" on my machine.

[Alexandr-Solovev]

@AlexZhao-becls You can launch dpc examples with host queue to check your performance on CPU. Can you share please result log of launching dpc examples? It should show results from both devices(cpu gpu).
examples/oneapi/cpp dont support queue and it uses only CPU version of the algorithm