Using KOKKOS_CLASS_LAMBDA in a class with Kokkos::Random_XorShift64_Pool member data

[Char-Aznable]

It seems to me that in order to use KOKKOS_CLASS_LAMBDA on device code, say CUDA, the class copy constructor has to be KOKKOS_FUNCTION. But the member Kokkos::Random_XorShift64_Pool data doesn't have KOKKOS_FUNCTION copy ctor so I'm stuck. Consider the following code for example:

#include <Kokkos_Core.hpp>
#include <Kokkos_DualView.hpp>
#include <Kokkos_Random.hpp>
#include <iostream>

using namespace std;

using ExecutionSpace = Kokkos::DefaultExecutionSpace;

struct Foo {

  KOKKOS_FUNCTION
  Foo(uint64_t rndSeed) : rndPool_(rndSeed) {};

  template < class E >
  KOKKOS_INLINE_FUNCTION void move() {
    
    using TeamPolicy = Kokkos::TeamPolicy<E>;
    using Team = typename TeamPolicy::member_type;
    TeamPolicy policy(100, 256);


    Kokkos::parallel_for(policy, KOKKOS_CLASS_LAMBDA (Team team) {
        auto rndEngine = rndPool_.get_state();
        int i = rndEngine.urand(0,10);
      }); 
  }

  Kokkos::Random_XorShift64_Pool<ExecutionSpace> rndPool_;
};



int main(int argc, char* argv[]) {
  Kokkos::initialize(argc,argv); {

  Foo d(829819);

  d.move<ExecutionSpace>();

  Kokkos::fence();

  } Kokkos::finalize();
}

This gives error in clang 6 + cuda 9:

testlambda.cpp:23:34: error: reference to __host__ function 'Foo' in __host__ __device__ function
    Kokkos::parallel_for(policy, KOKKOS_CLASS_LAMBDA (Team team) {

Is there a way around this? @ibaned I saw your https://github.com/ibaned/lambda_users_guide post but am I missing something here?

[Char-Aznable]

I've tried adding a copy ctor KOKKOS_FUNCTION Foo(const Foo& src) : rndPool_(src.rndPool_) {}; but this triggers the error:

testlambda.cpp:74:41: error: reference to __host__ function 'Random_XorShift64_Pool' in __host__ __device__ function
  KOKKOS_FUNCTION Foo(const Foo& src) : rndPool_(src.rndPool_) {};
                                        ^

[crtrott]

Ok this has something to do with the way how clang handles implicitly defaulted constructors. Basically you need to add the default constructors to your class:

  KOKKOS_FUNCTION
  Foo() = default;
  
  KOKKOS_FUNCTION
  Foo(const Foo&) = default;

And we need to add KOKKOS_INLINE_FUNCTION to the random pool classes for the default, the copy constructor and the assignment operator, but not the constructor which takes a seed.

[crtrott]

Just so you know I got a fix as part of some other thing I have been working on. Trying to get that in by tomorrow.

[crtrott]

Should be fixed in develop

[Char-Aznable]

The patch in develop branch works with or without explicitly marking Foo's default ctor KOKKOS_FUNCTION. Thanks a lot! @crtrott