#1 Add OpenACC compile option to autotools

[mlee03]

In this PR,

1. fregrid_acc and libfrencutils_acc directories have been created. The names of the files and the functions within have been changed with the suffix _acc. All OpenACC development for OpenACC enabled fregrid will occur in these two directories.
2. configure.ac and Makefile.am have been modified to append -acc compiler flag to FCFLAGS and to compile fregrid_acc

[rem1776]

I'm a bit confused by the copied over libfrencutils stuff. Is libfrencutils_acc a full copy of all the routines in the original libfrencutils with any gpu modifications needed? or is it supposed to only contain routines that were modified, with fregrid_acc using original versions when applicable?

I don't see fregrid_acc calling anything with the _acc added, so is it just using the orignal libfrencutils?

[mlee03]

@rem1776 currently in this PR, all files in the directories fregrid_acc and libfrencutils_acc are copies of those in fregrid and libfrencutils directories. The only difference is that the functions in the *_acc files have the suffix "_acc".
The compiled executablesfregrid and fregrid_acc at this point should be identical. The OpenACC changes will be merged in in a stepwise fashion to make the reviewing process and backtracing easier.

[rem1776]

@rem1776 currently in this PR, all files in the directories fregrid_acc and libfrencutils_acc are copies of those in fregrid and libfrencutils directories. The only difference is that the functions in the *_acc files have the suffix "_acc". The compiled executablesfregrid and fregrid_acc at this point should be identical. The OpenACC changes will be merged in in a stepwise fashion to make the reviewing process and backtracing easier.

So are you going to be removing the unused/unmodified routines in libfrencutils_acc as part of those updates?

If thats the case then i think we should probably only add those routines to begin with, maybe we can just add the acc versions to the same libfrencutils files instead of creating a copy? Saves us the confusion of having copies of things, and having to add a lot of code just to delete it since it'll all still be in the git history.

[mlee03]

Got it got it, yup I was going to remove functions as we go along (also thought it would be easier for debugging), but it is needless code that has to be carried around and removed functions that are needed in the future can be added back in. Okay, will remove all repetitive functions in fregrid_acc and libfrencutils_acc

[mlee03]

@rem1776 Perhaps it's ready. Decided to start almost from scratch.

[rem1776]

Looks good! thanks for making those changes i hope they weren't too annoying.

After this goes in I have an m4 file in the gpu_dev branch for the configure checks with the openacc flag, I'll make a PR for it. It'll just adjust the flag for different compilers if needed and make sure it works.

[mlee03]

No problem at all, I think this might be a better start for fregrid_acc. @bensonr @nikizadehgfdl @thomas-robinson @ceblanton, I think this PR is ready for your approvals 😇