Hi Michael,

thanks for your reply. I've built from scratch the Chapel version that
includes your changes on my laptop and it works correctly.
I'm mostly interested in LLVM-based communication optimizations for
Coarray Fortran; mainly because the LLVM optimization passes are
easier to create/modify than gfortran's.
I've already read the paper you mentioned (Ahayashi et al.) and I'm
quite suspicious about the generality of the proposed solution.
I'll send you a private email about this pretty soon.

Thanks for your support.

Regards,
Alessandro



2016-08-26 9:52 GMT-06:00 Michael Ferguson <[email protected]>:
> Hi Alessandro -
>
> Thanks very much for bringing up this issue, and for your interest
> in Chapel and --llvm-wide-opt [1].
>
> I've prepared a pull request that resolves the issue for me.
> I'm still testing this PR but I hope it will be merged sometime
> next week. It is here:
>
>  https://github.com/chapel-lang/chapel/pull/4412
>
> I'd be interested to know if that change resolves the issue
> for you and also what you plan to do with --llvm-wide-opt.
>
> I'll note that while --llvm-wide-opt is an exciting way to do
> communication optimization, it is still considered experimental.
> In particular, it doesn't run in nightly testing (although
> it probably should). I hope to improve upon it in the future
> but recently I have needed to focus on other efforts.
>
> Besides --llvm-wide-opt being experimental, there are a number
> of tasks that need to be done to really get the --llvm mode
> working as well as it could. I've listed these TODOs in the PR
> linked above. Of course, if you are interested in working on any
> of these, I'd be happy to help you get started. Also, if you're
> interested in using these LLVM-based communication optimizations
> in a different compiler, that's something I'd like to discuss
> as well. Discussion of either of these topics should probably
> move over to [email protected].
>
>>I installed the trunk version of Chapel on Edison (NERSC) choosing
>>llvm as back-end. Even the simplest helloworld case (without any
>>parallelism) leads to the following error (after about 2 minutes and
>>33 seconds of compilation process...):
>
> I can't tell if it took you 2+ minutes to run 'make' or the 'chpl' command.
> I'm guessing that you're talking about the 'chpl' command. On my system,
> the chpl command takes under 15 seconds in this case. Perhaps that
> compilation
> mode is particularly slow on Edison for some reason? Nonetheless we are
> aware that chpl compiles can take a long time.
>
>>$> chpl --llvm --llvm-wide-opt hello.chpl -o hello
>
> This is reasonable for testing, but note that if you want --llvm-wide-opt
> to do anything useful, you need to also pass --fast or another flag that
> causes most LLVM optimizations to run.
>
> Cheers,
>
> -michael
>
> [1] A paper about --llvm-wide-opt and also some other LLVM-based
>     communication optimization is available here:
>
> http://ahayashi.blogs.rice.edu/files/2013/07/Chapel_LLVM_camera_ready-q6usv
> 4.pdf
>

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