Windows support

[paulromano]

Now that OpenMC is solely C++ and Python, there's no fundamental reason why it shouldn't work on Windows. Supporting Windows would help encourage adoption in general. Some possible steps to help us get there:

• Try building/installing on Windows using Visual Studio
• Set up continuous integration to test on Windows (Azure Pipelines or AppVeyor)
• Distribute wheels on PyPI for Windows (see Distribution on PyPI? #1242)

[makeclean]

Building on Windows

1. Install Cmake for Windows
2. Install Git for Windows
3. Install Visual Studio15
4. Install HDF5 - now requires signup but there is native windows installer
5. open vstools native command prompt
6. cd to right place, for me I cloned in C:\Users\drand\openmc-test\openmc
7. mkdir bld
8. cmake -DCMAKE_INSTALL_PREFIX="C:\Users\drand\openmc-test\openmc" -Dopenmp=off C:\Users\drand\openmc-test\openmc note openmp I couldnt get to work right now
   
9. cmake --build . --config Release --target install *also doesnt quite work, errors from openmc::fatal_error
   
   and a bunch of complaints from the hdf5 interface, and about 748 other errors and some warnings.

Can I put the build log somewhere useful?

[paulromano]

@makeclean Absolutely, feel free to share the build log somewhere!

[pshriwise]

I was fussing around with this a bit today in Visual Studio '17 (couldn't get '19 to work at all).

I was able to successfully get hdf5 built and installed. Then got the following list of warnings/errors when attempting a build with OpenMC.

[makeclean]

I managed to get the number of errors down to about 115, which is two functions in the hdf5_interface. It seems like windows hdf5 doesn't like the hid_t datatype for some reason. Also the MS C++ compiler gives some weird errors, when the error is really upstream :(

[liangjg]

It seems one type of error that occurs many times and prevents MSVC from compiling openmc is due to the variable length array (VLA):

double evaluate_legendre(int n, const double data[], double x)
{
  double pnx[n + 1];
  ...
}

error C2131:  expression did not evaluate to a constant

• VLAs are only supported in C, and only from C99 on. They are not supported in C++.
• g++ supports VLAs as extensions to C90 and C++
• Visual Studio does not support VLAs at all in either C or C++. VS only supports up to the C89 standard
  To get around this, we can replace the VLAs with either dynamic arrays using new operator (must be deleted manually) or standard containers using std::vector. I guess the latter is more C++? But not sure if this will be less efficient than VLAs.

[paulromano]

@liangjg Ah-ha, good observation! Sounds like we ought to get rid of VLAs then since that is not standard C++. I'll create a separate issue for that.

[kingyue737]

I made some efforts to install openmc on Windows. I’m a newbie in c++, so the following speculation may not be correct.

Three options:
1、 compile with VC++:

• VC++ only supports OpenMP 2.0. Although I’ve built openmc successfully on windows, openmp is not available as @liangjg mentioned in Compiling OpenMC using Visual Studio #1249 .
• VC++ does not support C99. Cannot install OpenMC Python API because of C99 complex Fail to install Python API in Windows 10 #1601 . To address this issue, replace C99 complex with C++ complex (like what @liangjg did to get rid of C99 VLAs) may be an idea.

2、 compile with GCC-MinGW:

• I failed to compile with mingw. Some dependent libraries like HDF5 on my Windows are compiled with VC++. Official site only provides pre-built binary distributions complied with VC++. To test this option, a mingw HDF5 should be installed.

3、 compile with Clang-cl:

• Clang-cl is compatible with VC++. I’ve built openmc successfully with Clang-cl and tested with a pwr assembly example. Although Clang-cl support OpenMP 4.5, CMake can not find OpenMP due to a bug (https://gitlab.kitware.com/cmake/cmake/-/issues/20999)
• Python doesn’t fully support compiling with clang-cl on Windows now (https://bugs.python.org/issue33351). It’s hard to install Python API with clang-cl at present.

[kingyue737]

I tried these three options in Visual Studio 2019 CMake Open Folder, using three different predefined configurations:

[lonnietc]

Hello All,

I have just downloaded OpenMc and want to try to compile it on Windows using Visual Studio 2019 or MinGW-x64 and was wondering if you had any luck since the last post was 2020, it seems.

Thanks

[paulromano]

I'm not aware of any recent efforts to directly compile on Windows. These days with WSL, most people opt to go that route for using OpenMC on Windows. If you do try compiling through Visual Studio, let us know how it goes!

[lonnietc]

@paulromano I was just experimenting with my MinGW-x64 and OpenMC.

Had to fix a few definitions but seemed to be able to get it to compile to create.

openmc.exe
libopenmc.dll

test_distribution.exe
test_file_utils.exe

The test_file_utils.exe yields:

$ ./test_file_utils.exe
Randomness seeded to: 4020036940

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test_file_utils.exe is a Catch2 v3.1.1 host application.
Run with -? for options

-------------------------------------------------------------------------------
Test get_file_extension
-------------------------------------------------------------------------------
D:/msys64/home/lonni/openmc/tests/cpp_unit_tests/test_file_utils.cpp:6
...............................................................................

D:/msys64/home/lonni/openmc/tests/cpp_unit_tests/test_file_utils.cpp:14: FAILED:
  REQUIRE( get_file_extension("lovely.dir/extensionless_file") == "" )
with expansion:
  "dir/extensionless_file" == ""

===============================================================================
test cases:  3 | 2 passed | 1 failed
assertions: 10 | 9 passed | 1 failed

The test_distribution.exe yields:

$ ./test_distribution.exe
Randomness seeded to: 690677050
===============================================================================
All tests passed (14 assertions in 2 test cases)

And, openmc.exe yields (without any input files)

$ ./openmc.exe
 ERROR: Could not find any XML input files! In order to run OpenMC, you first
        need a set of input files; at a minimum, this includes settings.xml,
        geometry.xml, and materials.xml or a single model XML file. Please
        consult the user's guide at https://docs.openmc.org for further
        information.

I'm just now still very new to openmc as I want to try to compare it against MCNP6 for photon transports (i.e. Co60 irradiator that I want to model with OpenMC) to see how close they are in the simulations.

Is there some simple example that I can get to test an basic input xml file for the openmc.exe binary?

Also, does openmc need additional supporting datafiles for nuclear data?

Thanks and have a good day.