Windows support

[tcojean]

Visual Studio related problems

A potential issue are the compiler differences between Visual Studio and G++/Clang. It is possible that Ginkgo requires some bug fixes for proper Visual Studio support.

Shared library building

A known issue is that build fails on Windows due to missing shared libraries.

Seems that this stackoverflow question is related: https://stackoverflow.com/questions/33062728/cmake-link-shared-library-on-windows

It seems there is this generate_export_header command in CMake, which has to be done for every shared library we create, and the source code should be modified accordingly: https://cmake.org/cmake/help/v3.9/module/GenerateExportHeader.html

Some resources related to this:

• https://msdn.microsoft.com/en-us/library/ms235636.aspx
• http://dominoc925.blogspot.de/2016/08/use-cmake-to-help-build-and-use-windows.html

[yhmtsai]

Windows has the following options to compile C++ program.

1. Windows Subsystem for Linux (WSL)
   -- The compilation is not different from ubuntu.
   -- WSL 2 may support GPU access in the future. (But they set GPU access as the highest priority about two years ago)
2. MinGW
   It can be used by cmd or powershell. However, CUDA can not be compiled by MinGW.
3. Cygwin
   it depends on the installation of gcc.
4. Visual Studio
   -- The only one supports CUDA compilation in Windows.

I tried to see how to compile ginkgo static library in Visual Studio without CUDA.
I record the problem and how I solve it.

1. it can not recognize the overloaded template with enable_if correctly.
   For example,

template <typename T>
        static xstd::enable_if_t<is_complex<T>()> write_entry_impl(
            std::ostream &, const T &) {}
template <typename T>
        static xstd::enable_if_t<!is_complex<T>()> write_entry_impl(
            std::ostream &, const T &) {}

The compiler complain that the functions are redefined.
It can works with set the second template argument as template <typename T, int = 0>
The workaround solution can use this, to add one specified key.

2. isfinite is defined without any namespace, so the possible solution is similar to clang compiler.
   I only rename it in my try.
3. In core/test/stream the output 1234abcd -> 00001234abcd are different. the default string format might be different.
   e.g. Use ptrstream << std::hex << "0x" << reinterpret_cast<gko::uintptr>(&dummy); to ensure the same format here
4. Compiler can not find the correct function for clone(LinOp *). The line should use x->clone() not clone(x)

After doing these fixes, Visual Studio can compile ginkgo static library without CUDA.

[tcojean]

I am tentatively adding this to the v1.1.0 milestone as we have pretty much everything for this (except for merging @yhmtsai #351 PR). If this still needs a lot of stabilization and is not ready, this can be removed. We should at least have partial windows support (MinGW was merged and we are hopefully still compatible).

[yhmtsai]

For the MSVC unrecognized SFINAE, use constexpr member of struct not constexpr function.
original version:

template <typename T>
        static xstd::enable_if_t<is_complex<T>()> write_entry_impl(
            std::ostream &, const T &) {}
template <typename T>
        static xstd::enable_if_t<!is_complex<T>()> write_entry_impl(
            std::ostream &, const T &) {}

Fixed version

template <typename T>
        static xstd::enable_if_t<is_complex_s<T>::value> write_entry_impl(
            std::ostream &, const T &) {}
template <typename T>
        static xstd::enable_if_t<!is_complex_s<T>::value> write_entry_impl(
            std::ostream &, const T &) {}

For exporting shared library, set CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=TRUE to let cmake automatically export the symbols.

[tcojean]

We now have full windows support, so I will close this although it is still a good reference to point people to.