topic Re: About SYCL_EXTERNAL issue when separating defitions from declaration of a class in Intel® oneAPI DPC++/C++ Compiler

About SYCL_EXTERNAL issue when separating defitions from declaration of a class

PC-1 — Sun, 26 Feb 2023 09:32:35 GMT

I previously posted a similar question but not really get a solution. Suppose I need to call a function object and its member function in a kernel:

____________________

Q.submit([&](sycl::handler& h) {

sycl::accessor A(B, h);
h.parallel_for(size, [=](auto& idx) {
my_class& mc_ref =A[idx];
mc_ref.update(); //call member function of my_class
}
);
});

________

According to SYCL specifications, I need to define "my_class" and corresponding member function "my_class::update()" in one header, like

in "my_class.h"_____________

class my_class{

.....

void update() { .... ; return; }

.....

};

________________

Hoever, if I separate definition from class declaration, like

in "my_class.h"_____________

class my_class{

.....

void update() ;

.....

};

in "my_class.cpp"_____________

void my_class::update() { ... ; return;}

___________________________

It would generate compiler error : SYCL kernel cannot call an undefined function without SYCL_EXTERNAL attribute, since the member function is now defined under a different translation unit.

My question is that if there is anyway, or how can I declare "SYCL_EXTERNAL" in this situation so that I can separate class definiton from declaration ??

I need to do this because my code is a little compilcated, and in "my_class" there would be another class objects. (I usually manage data and abstration by C++ class).

If I put all defitions of member functions in one header file, it would be more than 5k lines... which I think is a little crazy and hard to read.

Could anyone provide me an example or some suggestions on how to organize my program in this case?

Thanks so much!

__________

Re: About SYCL_EXTERNAL issue when separating defitions from declaration of a class

RabiyaSK_Intel — Tue, 28 Feb 2023 16:01:15 GMT

Hi,

Thanks for posting in Intel Communities.

>>My question is that if there is anyway, or how can I declare "SYCL_EXTERNAL" in this situation so that I can separate class definiton from declaration ??

Yes, you can provide function declaration in a class and it's definition in another file but as per SYCL specifications, the function will come under different translation unit. Please make sure to include "SYCL_EXTERNAL" before function declaration in your header file.

Please go through the modified code files to understand it better.

main.cpp

#include "my_class1.h" int main() { size_t N = 4; sycl::buffer<int> B(N); { sycl::host_accessor a(B, sycl::write_only); for (int i = 0; i < N; i++) { a[i] = i; } } queue Q; Q.submit([&](sycl::handler& h) { sycl::accessor A(B, h); h.parallel_for(N, [=](item<1> i) { my_class mc_ref; mc_ref.update(A, i); //call member function of my_class }); }); host_accessor h{B}; for(int i=0;i<N;i++) std::cout<<h[i]<<" "; return 0; }

my_class.cpp

#include "my_class1.h" //Methods void my_class::update(cl::sycl::accessor<int, 1, cl::sycl::access::mode::read_write> A, cl::sycl::item<1> i) { int idx=i.get_id(); A[idx]=A[idx]+1; }

my_class1.h

#pragma once #include<iostream> #include<CL/sycl.hpp> using namespace sycl; class my_class{ public: //extern SYCL_EXTERNAL void update(cl::sycl::accessor<int, 1, cl::sycl::access::mode::read_write> A, cl::sycl::item<1> i); };

Hope this resolves your issue, if you still face any issues please share the sample reproducer code with us.

Thanks & regards,

Shaik Rabiya

Re: About SYCL_EXTERNAL issue when separating defitions from declaration of a class

PC-1 — Thu, 02 Mar 2023 00:30:19 GMT

Thanks so much, Shaik!

I tried your code and it works.

The reason I got stuck here is because I always think "extern" can only be used for a variable or a function, instead of a class member function....

I know that my question is very fundamental and is probably not worth for you spending time to provide an answer : )

Anyway, really thanks!

Best regards,

Re:About SYCL_EXTERNAL issue when separating defitions from declaration of a class

RabiyaSK_Intel — Thu, 02 Mar 2023 10:31:14 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,

Shaik Rabiya