Add shared file testing to test_api

[mcfadden8]

A new option (--shared-file) was added to test_api that will cause all of the participating ranks to share the same file with each process using a unique section of the file for its I/O operations.

[mcfadden8]

@adammoody - I have marked the comments as resolved. I attempted to simplify file creation logic at the cost of an MPI_Bcast call. Let me know if you think that is ok

[adammoody]

@adammoody - I have marked the comments as resolved. I attempted to simplify file creation logic at the cost of an MPI_Bcast call. Let me know if you think that is ok

Hmm, that's shorter code, but I think it's a bit hard to follow.

Let's keep with using the separate code paths as it's easier to understand. But we could simplify this section of the code by defining a new "create_file" function. That would do the magic to create/open the file (either shared or file per process) and return an opened file descriptor that is ready for writing. This part would thenreduce to something like:

int fd_me = create_file(fname);

while we move your previous code block into the create file function, so something like:

int create_file(fname) {
  if (shared_file) {
    if (rank == 0) {
      open()
      truncate()
      close()
    }
    barrier() or bcast() to wait on rank 0
    return open(fname, ...)
  } else {
    return open(fname, ...)
  }
}

[mcfadden8]

Okay take 3. I like the structure proposed, but it does expand for error handling. Thoughts?

[adammoody]

Looks good. Thanks!

[adammoody]

oh, wait. I think fd==0 also means success, right?

[adammoody]

and if that's true, I have that bug all throughout the test_*.c code.

[adammoody]

whoops!

[mcfadden8]

Yeah, I had noticed that too. But it is rare that stdin, stdout, and/or stderr would be closed. But I suppose it could happen. I'll clean this up

[adammoody]

Thanks, @mcfadden8 . This looks good to me. Ready to be merged from your view?

[mcfadden8]

This looks ready to me. I'm finished with my changes.

[adammoody]

Thanks @mcfadden8 !