topic Re: problems about SYCL reduction variables using oneAPI in Intel® oneAPI DPC++/C++ Compiler

problems about SYCL reduction variables using oneAPI

JamesFBM — Tue, 07 Feb 2023 09:30:14 GMT

Hi, I'm new to SYCL and am trying to run an example about reduction variables from the SYCL Specification with oneAPI 2023.0.0. I revise the code a little and the final version is shown as follows:

#include <iostream> #include <sycl/sycl.hpp> #include <numeric> using namespace sycl; int main() { buffer<int> valuesBuf{ 1024 }; { host_accessor a{ valuesBuf }; // std::iota(a.begin(), a.end(), 0); std::iota(&(a[0]), &(a[1023]), 0); } int sumResult = 0; buffer<int> sumBuf{ &sumResult, 1 }; int maxResult = 0; buffer<int> maxBuf{ &maxResult, 1 }; queue myQueue; myQueue.submit([&](handler& cgh) { auto inputValues = valuesBuf.get_access<access_mode::read>(cgh); auto sumReduction = reduction(sumBuf, cgh, plus<>()); auto maxReduction = reduction(maxBuf, cgh, maximum<>()); /* cgh.parallel_for(range<1> {2048, 1024}, sumReduction, maxReduction, [=](nd_item<1> it, auto& sum, auto& max) { sum += inputValues[it.get_local_id()]; max.combine(inputValues[it.get_global_id()]); }); */ cgh.parallel_for(nd_range<1> {2048, 1024}, sumReduction, maxReduction, [=](nd_item<1> it, auto& sum, auto& max) { sum += inputValues[it.get_local_id()]; max.combine(inputValues[it.get_local_id()]); }); }); // assert(maxBuf.get_host_access()[0] == 1023 && sumBuf.get_host_access()[0] == 523776); std::cout << maxBuf.get_host_access()[0] << std::endl; std::cout << sumBuf.get_host_access()[0] << std::endl; }

However, the program compiled with icpx in cmd does not work as expected. The program typically prints out nothing and exits with a meaningless value. The result is shown below:

C:\Users\a1595\Desktop\dr\c>icpx -fsycl c.cpp -o c.exe C:\Users\a1595\Desktop\dr\c>c.exe C:\Users\a1595\Desktop\dr\c>echo %ERRORLEVEL% -1073740791

I am wondering whether there is anything wrong with the code, compilation or anything else.

I am looking forward to any help. Thanks a lot.

Re: problems about SYCL reduction variables using oneAPI

SeshaP_Intel — Thu, 09 Feb 2023 05:15:18 GMT

Hi,

Thank you for posting in Intel Communities.

Please find the below modified DPC++ source code which is producing the correct values after the execution.

#include <iostream> #include <CL/sycl.hpp> #include <numeric> using namespace sycl; int main() { buffer<int> valuesBuf { 1024 }; { host_accessor a { valuesBuf }; std::iota(&a[0], &a[0] + 1024, 0); } int sumResult = 0; buffer<int> sumBuf { &sumResult, 1 }; int maxResult = 0; buffer<int> maxBuf{ &maxResult, 1 }; queue myQueue; myQueue.submit([&](handler& cgh) { auto inputValues = valuesBuf.get_access<access_mode::read>(cgh); auto sumReduction = reduction(sumBuf, cgh, plus<>()); auto maxReduction = reduction(maxBuf, cgh, maximum<>()); cgh.parallel_for(nd_range<1> {1024, 256}, sumReduction, maxReduction, [=](nd_item<1> it, auto& sum, auto& max) { sum+= inputValues[it.get_global_id()]; max.combine(inputValues[it.get_global_id()]); }); }); std::cout << "maxReduction = "<<maxBuf.get_host_access()[0] << std::endl; std::cout << "sumReduction = "<<sumBuf.get_host_access()[0] << std::endl; return 0; }

Please find the output screenshot below.

Hope this resolves your issue.

Thanks and Regards,

Pendyala Sesha Srinivas

Re: problems about SYCL reduction variables using oneAPI

JamesFBM — Tue, 14 Feb 2023 13:33:15 GMT

Hi, Sesha. Thanks a lot for your help. Your code works on my computer and I simply misunderstood the usage of nd_range.

Re: problems about SYCL reduction variables using oneAPI

PC-1 — Wed, 15 Feb 2023 05:12:56 GMT

Hi, SeshaP,

Unfortunately I cannot compile you code in visual studio 2022..

Error message is "error : SYCL kernel cannot call a variadic function"

and "error : SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute"

Could you help me with that?

Re: problems about SYCL reduction variables using oneAPI

SeshaP_Intel — Wed, 15 Feb 2023 06:07:56 GMT

Hi,

Thanks for accepting our solution.

>> Unfortunately I cannot compile you code in visual studio 2022.

Please refer to the below output screenshot built on Visual Studio in Release Mode.

If you need any additional information, please post a new question as this thread will no longer be monitored by Intel.

Thanks and Regards,

Pendyala Sesha Srinivas