topic Re: SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute in Intel® oneAPI DPC++/C++ Compiler

SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

amaltaha — Mon, 09 May 2022 15:07:54 GMT

I am trying to calculate the euclidean distance for KNN but in parallel using dpc++. the training dataset contains 5 features and 1600 rows, while I want to calculate the distance between the current test point and each training point on the grid in parallel, but I keep getting an error regarding sycl kernal. code for the function:

std::vector<double> distance_calculation_FPGA(queue& q,const std::vector<std::vector<double>>& dataset,const std::vector<double>& curr_test) { range<1> num_items{ dataset.size()}; std::vector<double>res; res.resize(dataset.size()); buffer dataset_buf(dataset); buffer curr_test_buf(curr_test); buffer res_buf(res.data(), num_items); q.submit([&](handler& h) { accessor a(dataset_buf, h, read_only); accessor b(curr_test_buf, h, read_only); accessor dif(res_buf, h, write_only, no_init); h.parallel_for(num_items, [=](auto i) { for (int j = 0; j <(const int) a[i].size(); ++j) { dif[i] += (a[i][j] - b[j]) * (a[i][j] - b[j]) ; } }); }); for (int i = 0; i < res.size(); ++i) { std::cout << res[i] << std::endl; } //old distance calculation (serial) //for (int i = 0; i < dataset.size(); ++i) { // double dis = 0; // for (int j = 0; j < dataset[i].size(); ++j) { // dis += (curr_test[j] - dataset[i][j]) * (curr_test[j] - dataset[i][j]); //} //res.push_back(dis); //} return res; }

the error I am receiving:

SYCL kernel cannot call a variadic function

SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

Would be extremely grateful for any help!

Thanks

Re: SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

SantoshY_Intel — Mon, 09 May 2022 10:42:40 GMT

Hi,

Thank you for posting in Intel Communities.

We assume that you are using the following scenario:

Trying to launch the distance_calculation_FPGA() function inside an SYCL kernel and printing its return value.

To resolve your issue, you can use the below workaround:

1. Create a header file (example: Header.h) and declare the function as "SYCL_EXTERNAL"

#include<CL/sycl.hpp> extern SYCL_EXTERNAL std::vector<double> distance_calculation_FPGA(queue& q,const std::vector<std::vector<double>>& dataset,const std::vector<double>& curr_test);

2. Now include the header file in your source code.

#include <CL/sycl.hpp> #include "Header.h" std::vector<double> distance_calculation_FPGA(queue& q,const std::vector<std::vector<double>>& dataset,const std::vector<double>& curr_test){ }

3. Try to recompile and run your program.

If this resolves your issue, make sure to accept this as a solution. This would help others with a similar issue.

If you still face any issues, then please provide us with the complete sample reproducer code and steps to reproduce your issue from our end.

Thanks & Regards,

Santosh

Re: SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

amaltaha — Mon, 09 May 2022 15:07:10 GMT

I am not calling the function inside the kernel, actually, the problem lies in the way I am doing the parallelism in parallel_for:

so it works normally if I do this:

h.parallel_for(num_items, [=](auto i) { for (int j = 0; j <(const int) a[i].size(); ++j) { dif[i] += a[i]; } });

but when I try to take the values in the second dimension like this:

h.parallel_for(num_items, [=](auto i) { for (int j = 0; j <(const int) a[i].size(); ++j) { dif[i] += a[i][j] ; } });

It gives an error.

please see the previous full code, I don't know if I defined the buffers and accessors correctly.

I tried to do the solution you provided, but it gave me many errors more than before, so it is not working, unfortunately.

Re: SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

SantoshY_Intel — Thu, 12 May 2022 08:49:42 GMT

Hi,

We tried running your code by creating dummy 'dataset' and 'curr_test' variables. We were able to run the program successfully as shown in the below screenshot.

Please refer to the complete code attached below.

#include <CL/sycl.hpp> #include <iostream> using namespace sycl; std::vector<double> distance_calculation_FPGA(queue& q,const std::vector<std::vector<double>>& dataset,const std::vector<double>& curr_test) { range<1> num_items{ dataset.size()}; std::vector<double>res; res.resize(dataset.size()); buffer dataset_buf(dataset); buffer curr_test_buf(curr_test); buffer res_buf(res.data(), num_items); q.submit([&](handler& h) { accessor a(dataset_buf, h, read_only); accessor b(curr_test_buf, h, read_only); accessor dif(res_buf, h, write_only, no_init); h.parallel_for(num_items, [=](auto i) { for (int j = 0; j <(const int) a[i].size(); ++j) { // dif[i] += (a[i][j] - b[j]) * (a[i][j] - b[j]) ; dif[i]+=a[i][j]; } }); }); q.wait(); //We have added this line of code for synchronization. for (int i : res) { std::cout <<i<< std::endl; } return res; } int main(){ std::vector<std::vector<double>> dataset; for(int i=0;i<5;i++) { std::vector<double> d; for(int j=0;j<1600;j++) { d.push_back((double)j); } dataset.push_back(d); } std::vector<double> curr_test; for(int i=0;i<1600;i++) { curr_test.push_back((double)i); } queue q; std::cout << "Running on "<< q.get_device().get_info<sycl::info::device::name>()<< std::endl; //print the device name as a test to check the parallelisation distance_calculation_FPGA(q,dataset,curr_test); return 0; }

Thanks & Regards,

Santosh

Re: SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

amaltaha — Thu, 12 May 2022 21:53:32 GMT

Hello,
Thank you so much for the support, actually I am using Microsoft Visual Studio 2022 to run OneAPI compiler for dpc++. I tried to run your code in it but it gave me the same exact error. But I tried to run in on the cloud like the screenshot, and it worked normally. Very Glad I was able to run it on the cloud though thank you so much.
I solved the problem in Visual Studio by making a one-dimensional vector<double> instead of vector<vector<double>> and accessed the elements I wanted by x + y * col.

I really appreciate the very professional efforts and support from you.

Thank you!

Re:SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute

SantoshY_Intel — Fri, 13 May 2022 08:03:27 GMT

Hi,

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

Thanks & Regards,

Santosh