Windows support

[zbeekman]

coverage on master

Summary of changes

• Support building OpenCoarrays natively on Windows without relying on WSL or other heavyweight options using GCC/GFortran 11 and Intel MPI
• CMake build system can now better handle spaces in paths in most/many cases (this is quite common on Windows machines)
• A probable bug was fixed in which a CMake generator expression was used in a try_compile() statement. This was definitely breaking windows builds and seems like it should have been breaking linux & macOS builds too, since the try_compile() doesn't cause an actual build system generation so the angle bracket syntax text of the generator expression was just getting injected directly into a makefile or compile command.
• Mostly updated & modernized the usage of the overhauled FindMPI CMake module--deprecated variables and options were removed in favor of their modern counterparts, but a few instances of the old variables may have been overlooked.
• The caf and cafrun scripts were made more robust which in turn lets them be called directly from a bash or bash-like shell on Windows or a native Windows cmd.exe shell (with Git BASH installed). A long standing typo in the caf script was also fixed 😄
• Utilize more intelligent threading library support provided by CMake since the opencoarrays runtime library explicitly utilizes pthreads. On windows this is potentially an issue, and, at the very least, the caf wrapper script will need to ensure that the compiler/linker enables a pthread compatible threading solution. This should make the build more robust on other platforms too.

Rationale for changes

These changes were made to support the ability to build and run OpenCoarrays and therefore coarray Fortran applications on Windows and to generally improve the robustness of the build system. WSL and other heavyweight *nix compatibility solutions are often unpalatable or unacceptable to some users and organizations. Requiring the now freely available Intel MPI implementation (part of Intel's OneAPI set of developer tools) is acceptable because 1) It's the only sufficiently modern and up-to-date MPI solution that I am aware that runs natively on windows, 2) it is now available free of cost and 3) many HPC computing centers, government agencies, etc. already have support contracts with Intel and use the Intel compilers/OneAPI. In addition to Intel OneAPI, the GFortran and GCC native windows compilers are required along with CMake and unix make/gmake, and a bash shell like the one that comes with git-bash for windows. Binaries produced with the OpenCoarrays caf wrapper script should be redistributable without all these other requirements--only requiring the intel MPI runtime--assuming that the user doesn't intentionally try to create dynamically linked executables.

ToDo

• [x] Add documentation about using/building on windows
• [x] Fix the perl style tests and shell script tests on windows (this might just mean disabling them)
• [ ] Add windows CI testing
• [x] Create a batch file wrapper version of the caf and cafrun scripts so the build will proceed under powershell or cmd.exe (But you'll still need bash installed somewhere & on the path) The batchfile would just pass arguments through to caf/cafrun.
• [x] Try to get CMake's findMPI module working on windows... right now my work around is a hack and this would make things more robust
• [x] Verify modern usage of FindMPI has been updated everywhere and bump CMake minimum version and policies accordingly.
• [x] Verify redistributability of statically linked binaries built with caf wrapper script
• [x] Test if caf wrapper script encapsulates all the required intel MPI environment information to be used outside of the intel configured CMD.exe shell.
• [x] Investigate what the installation currently does on windows, get it working if it is broken and figure out what a good/canonical install location and directory structure would be.

Additional info and certifications

This pull request (PR) is a:

• [x] Bug fix
• [x] Feature addition
• [ ] Other, Please describe:

I certify that

• [x] I certify that:
  • I have reviewed and followed the contributing guidelines
  • I will wait at least 24 hours before self-approving the PR to give another OpenCoarrays developer a chance to review my proposed code
  • I have not introduced errant white space (no trailing white space or white space errors may be introduced)
  • I have added an explanation of what these changes do and why they should be included
  • I have checked to ensure there aren't other open Pull Requests for the same change
  • I have you written new tests for these changes
  • I have successfully tested these changes locally
  • I have commented any non-trivial, non-obvious code changes
  • The commits are logically atomic, self consistent and coherent
  • The commit messages follow best practices
  • Test coverage is maintained or increased after this is merged

Code coverage data

[zbeekman]

@everythingfunctional thanks so much for the test drive and review!!! I'm impressed and happy that you got so far without any adequate documentation. This is my first priority and on the top of my todo list and I requirement before I change this PR from draft status.

I used a Windows Command Prompt. I first ran the setvars.bat script provided by Intel to setup the environment. I created opencoarrays-build and opencoarrays-install folders. From the opencoarrays-build folder, I used cmake-gui ../OpenCoarrays to set the Generator to "Unix Makefiles", the compilers to those installed by the Equation.com gcc installer, and the install folder to opencoarrays-install. I was then able to, from the same command prompt, run make and the make test to compile and run the test suite. A few tests failed, specifically register_alloc_comp_1,2 and 3, test-installation-scripts.sh, caf, and cafrun. It also popped up a lot of prompts from Windows Defender, but they did not reappear after having accepted them all and running the suite again. The failure of the last 3 tests is probably expected, since a Windows command prompt doesn't understand how to execute a shell script. make install then copied the expected things over to opencoarrays-install. From a git-bash terminal I can then use the provided caf and cafrun scripts to compile and execute a "Hello, World", although each image segfaults on program shutdown. Using fpm with caf and cafrun does not work however, as it uses execute_command_line, which executes in a cmd environment, which can't execute the scripts.

These are known issues, some/most of which are documented in the todo list in the main PR comment/description

• register_alloc_comp_{1..3} fail for me as well, and, do so on macOS as well: They fail with MPICH too, but not OpenMPI, IIRC. So this issue isn't limited to windows. This appears to be a bug in OpenCoarrays most likely, or MPICH based MPI implementations, or in my introspection build logic.
• The final test failures need better logic to guard against executing them in an environment missing developer specific packages like perl and are testing style things mostly. This is something I plan to fix/improve before merging.
• Concerning shells and fpm: I'm contemplating ways of trying to improve shell portability and alternative options. Right now the caf and cafrun scripts are the only thing preventing the build & testing to be able to take place entirely within a native CMD or powershell environment AKAICT. I'm brainstorming ways to create thin wrappers to call them from a CMD.exe shell or similar. Likewise, Find_MPI isn't working from the bash shell, likely because the MPI compiler wrapper scripts provided by Intel are batch files and can't be executed from a bash shell in a straightforward way. I'm still contemplating ways to improve general useability and cut out or abstract and upstream complexity.
• The program segfault on exit is something I have been seeing too. Interestingly, with a slightly different (older) version of IntelOneAPI and pulling in a windowspthread implementation that I wasn't picking up in my environment they don't see this problem. I should check if some of the pthread locking calls are made during shutdown/finalization. I seem to recall having this problem or a similar problem with certain MPI implementations on macOS as well. So it may be a bigger OC or MPI implementation bug.

In all, I think this is a huge leap forward, but I would ask for at least one additional thing to be included in this PR. Update the README.md and/or INSTALL.md to provide better instructions for building and using on Windows. A future PR for use of caf and cafrun in a native Windows environment would be a good idea, but it's not super urgent.

I completely agree. Lack of documentation is the number one blocker of this PR and an absolute requirement before merging. That's why it's at the top of the ToDo list. 😉

Thanks again for the feedback!

I've pasted the segfault during shutdown info from a debug build below in the event that you or @vehre have any insight into what's happening.

$ cafrun -np 2 ./hello_caf.exe
 Hello from            2  of            2 !
 Hello from            1  of            2 !

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0  0xadf38fdb
#1  0xadf2ef04
#2  0xadf0fef1
#3  0x78797ff7
#4  0x78ab20ce
#5  0x78a61453
#6  0x78ab0bfd
#7  0xadf27185
#8  0xadee3471
#9  0xadee34e7
#10  0xadee1683
#11  0xadee13c0
#12  0xadee14f5
#13  0x784f7033
#14  0x78a62650
#15  0xffffffff

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0  0xadf38fdb
#1  0xadf2ef04
#2  0xadf0fef1
#3  0x78797ff7
#4  0x78ab20ce
#5  0x78a61453
#6  0x78ab0bfd
#7  0xadf27185
#8  0xadee3471
#9  0xadee34e7
#10  0xadee1683
#11  0xadee13c0
#12  0xadee14f5
#13  0x784f7033
#14  0x78a62650
#15  0xffffffff
1/2: _gfortran_caf_init(957) The mpi memory model is: unified  (0x2, 1).
1/2: finalize_internal(972) (status_code = 0)
1/2: finalize_internal(1026) In barrier for finalize...1/2: finalize_internal(1059) Freed all slave tokens.
2/2: finalize_internal(972) (status_code = 0)
2/2: finalize_internal(1026) In barrier for finalize...2/2: finalize_internal(1059) Freed all slave tokens.
Error: Command:
   `C:/Program Files (x86)/Intel/oneAPI/mpi/latest/bin/mpiexec.exe -np 2 ./hello_caf.exe`
failed to run.

[zbeekman]

@everythingfunctional @rouson let me know if the updated build instructions in INSTALL.md make sense and you can follow them. WSL's bash can cause problems, and I know the instructions are somewhat long and involved but I tried to have a good mix of hand-holding and robustly doing things on the users end; more advanced users will probably see shortcuts and alternative routes to get to the same endpoint.

Also, I've added batch-script wrappers for caf and cafrun. If the bin subdirectory of the opencoarrays installation directory is on your path, you should be able to call caf and cafrun natively, and hopefully (untested 🤞) this means you might be able to pass them as the compiler to fpm.

[zbeekman]

@rouson @everythingfunctional Thanks so much for the reviews! Many great suggestions and improvements.

@rouson Please see this comment (1) and this comment (2) about "Git-Bash" vs "Git BASH" and "a Git-Bash bash shell" vs "a Git BASH shell" respectively. Right now I think the original wording/phrasing should stand unless I'm misunderstanding something.

@everythingfunctional I would like my wording/explanation to be clearer too, but think that the repetitive phrasing should stay, as explained in this comment unless there is a better way to say it. (But I can't think of one.)

[rouson]

@zbeekman all looks great. Thanks again!