Flang support

[marchdf]

Hi, I was using the flang compiler on Frontier today (which I was using for openfast) but I got errors in ROSCO when using the same compiler. I noticed in the cmake that ROSCO only supports GNU and Intel compilers:

ROSCO/rosco/controller/CMakeLists.txt

Line 44 in b994e4d

if (${CMAKE_Fortran_COMPILER_ID} STREQUAL "GNU")

. I was hoping there was a path towards supporting flang so that I don't have to mix compilers. Thanks!

[dzalkind]

Hi,

Interesting! I'm not that familiar with Flang and may not have the bandwidth to tackle (and, mainly, test a fix for) this issue very soon, but there's definitely a path towards its support. The process should be

• Adding these lines to the ROSCO CMakeLists.txt that you linked.
• Adding the SysFlangLinux.f90 file to the ROSCO sys files
• Tidying up the sys file to match the other in ROSCO, which mainly consists of removing some extra submodules and compiler directives. I did a quick diff between the OpenFAST and ROSCO SysFiles.

I hope this helps. I'll leave this open until we're supporting Flang. If you're able to get to it before we do, we'd greatly appreciate any tips or a PR.

Best, Dan

[marchdf]

Thanks for answering so quickly! If I get a chance I might give your suggestion a shot.

[marchdf]

@dzalkind I needed this for frontier and I have a working version. But it's for ROSCO 2.7 because those are the input files I was given. Here's the branch: https://github.com/marchdf/ROSCO/tree/rosco-27-flang. Let me know if that "looks" ok and I can try doing the same for the dev version of ROSCO and submit a PR.

[dzalkind]

Thanks, Marc! It looks okay to me. Ideally, we'd figure out how to keep these lines as they are ROSCO's main debugging output.

Apparently there are a bunch of Flang flavors out there, with a new one due in March. Maybe it will resolve the issue you raised. Which Flang compiler you are using on frontier?

[marchdf]

Yes I definitely think the eventual PR should have those lines in there. I am going to work with someone who knows fortran/flang better than me and see if we can resolve this. I am a bit confused by the flang landscape. Let me get back to on what kind of version I am using.

[dzalkind]

@ndevelder is also interested in flang support (#397)

I don't have a set up with flang, so it's hard for me to make the required fixes to this source code. If either of you are able to help me with that, I could support this better.

[marchdf]

That would be fantastic and if you had something, I would be happy to test. Here is a link to my branch that made v2.7 work: https://github.com/marchdf/ROSCO/tree/rosco-27-flang. Please feel free to adapt for newer versions and I can try it out.

[dzalkind]

Great! I'll bring your branch up to date.

The only real hang up was that flang didn't like this: marchdf@cb5005e#diff-24535ca502db14768af01d975fd720e3fd71b2986252bd59cda15e89af2f13f2L519

That bit of code is used to see the internal signals of ROSCO, so it could be something we just omit from flang builds with a compile-time flag.