simplification of workdiv creation

[mehmetyusufoglu]

Workdiv constructor needs 2 class template parameters and 3 alpaka::Vec arguments.
auto const workdiv = alpaka::WorkDivMembers<Dim, Idx>{arraySize / blockSize, (int)blockSize, 1u};

The aim is being able to create workdiv, without template parameters, for example
auto const workdiv = createWorkDiv(arraySize / blockSize, blockSize, 1);

Update: Factory method is not used, a new constructor is introduced, no need for explicit type params in the new constructor call. All 3 input types must be alpaka::Vec with the same TDim type. auto const workDiv2D = alpaka::WorkDivMembers(blocksPerGrid2D, threadsPerBlock2D, elementsPerThread2D);

Another PR [2243] is provided onto this one, for using std::array instead of alpaka vectors as arguments. Class template parameters are not needed.

[bernhardmgruber]

Why can't we just add such a constructor to WorkDivMembers and a deduction guide if necessary?

[mehmetyusufoglu]

Yes, but I wanted to use "create..." since I will add new similar functions. Using create functions seemed cleaner for conversions from stl container types and initializer lists.

By the way; I think you mean deduction guides for constructors as the one below, since they don't have a return type?:

template<class A, class B>
struct Agg
{
    A a;
    B b;
};
// implicitly-generated guides are formed from default, copy, and move constructors
 
template<class A, class B>
Agg(A a, B b) -> Agg<A, B>;

[mehmetyusufoglu]

Currently we cannot use stl containers, argument types are constrained to alpaka vector and buffer.

[bernhardmgruber]

Yes, but I wanted to use "create..." since I will add new similar functions. Using create functions seemed cleaner for conversions from stl container types and initializer lists.

I beg to disagree. Constructors are the C++ way to construct an object. There are limited use cases for factory functions, but if a constructor will do fine, use one. You can overload them if you need to convert from various sources.

By the way; I think you mean deduction guides for constructors as the one below, since they don't have a return type?:

template<class A, class B>
struct Agg
{
    A a;
    B b;
};
// implicitly-generated guides are formed from default, copy, and move constructors
 
template<class A, class B>
Agg(A a, B b) -> Agg<A, B>;

Yes, I mean this kind of deduction guide. But it turns out, that one is not necessary here.

Currently we cannot use stl containers, argument types are constrained to alpaka vector and buffer.

Alright, you don't need one here :)

[mehmetyusufoglu]

Ok, I moved the createWorkDiv function as a new constructor. This PR could be merged, then I will prepare a second PR for the array or initilizer list type of inputs without explicit type parameters.

[mehmetyusufoglu]

It needed a deduction guide (hence a seperate constructor declaration with deduction guide) for some compilers.

[bernhardmgruber]

Just tried it, if you add the constructor:

        ALPAKA_FN_HOST_ACC WorkDivMembers(
            alpaka::Vec<TDim, TIdx> const& gridBlockExtent,
            alpaka::Vec<TDim, TIdx> const& blockThreadExtent,
            alpaka::Vec<TDim, TIdx> const& elemExtent)
            : m_gridBlockExtent(gridBlockExtent)
            , m_blockThreadExtent(blockThreadExtent)
            , m_threadElemExtent(elemExtent)
        {
        }

your unit test can be written using:

    auto ref = alpaka::WorkDivMembers(blocksPerGrid3D, threadsPerBlock3D, elementsPerThread3D);

and compiles and passes the tests.

[bernhardmgruber]

Suggested change

	//! Deduction guide for the constructor which can be called without explicit template type parameters
	ALPAKA_NO_HOST_ACC_WARNING
	template<typename TDim, typename TIdx>
	ALPAKA_FN_HOST_ACC explicit WorkDivMembers(
	alpaka::Vec<TDim, TIdx> const& gridBlockExtent,
	alpaka::Vec<TDim, TIdx> const& blockThreadExtent,
	alpaka::Vec<TDim, TIdx> const& elemExtent) -> WorkDivMembers<TDim, TIdx>;
	template<typename TDim, typename TIdx>
	ALPAKA_FN_HOST_ACC WorkDivMembers(
	alpaka::Vec<TDim, TIdx> const& gridBlockExtent,
	alpaka::Vec<TDim, TIdx> const& blockThreadExtent,
	alpaka::Vec<TDim, TIdx> const& elemExtent) -> WorkDivMembers<TDim, TIdx>;

I am not even sure if doxygen supports documenting deduction guides. I would just leave it here.

Different question: I did not need a deduction guide for g++-13. Is the deduction guide provided as a workaround for some compilers? If yes, could you maybe document them here, so we can remove the deduction guide when we phase out those compilers?

[mehmetyusufoglu]

There were many compilers, yes I can document. Thanks. ( I might return to create... functions idea because now I am trying to call WorkDivMembers constructor without constraining the arguments to alpaka vector. )

[mehmetyusufoglu]

The comment is important for the developers

[psychocoderHPC]

we need to fix the OSX CI before we can merge this.

[psychocoderHPC]

@mehmetyusufoglu could you please rebase this against the develop branch? I merged the OSX CI fix

[bernhardmgruber]

One more small nit: