[LLVMdev] [GSoC] Flang's end of GSoC report

"C. Bergström" cbergstrom at pathscale.com
Mon Sep 23 10:44:38 PDT 2013

On 09/24/13 12:16 AM, Chris Lattner wrote:
> On Sep 23, 2013, at 10:01 AM, C. Bergström <cbergstrom at pathscale.com> wrote:
>> On 09/23/13 11:54 PM, Chris Lattner wrote:
>>> On Sep 23, 2013, at 5:25 AM, Alex L <arphaman at gmail.com <mailto:arphaman at gmail.com>> wrote:
>>>> Hi everyone!
>>>> Today is the official "pencils down" day for GSoC and I wrote a report describing what results I've achieved since my last report in July:
>>>> http://flang-gsoc.blogspot.ie/2013/09/end-of-gsoc-report.html
>>>> Thanks for this GSoC LLVM!
>>> Wow, this is really fantastic work.  I'm surprised and impressed by how much progress you made.
>>> Can you comment more about Pathscale's plans, and why they don't want to release the code?
>> Initially the code will continue to be developed privately, but there's a big ?<question mark> and sticky note to look at what makes best sense - It's a conservative approach, but that's how it is for now.
> Do you have specific goals here?  This is not a great way to foster the community and get contributions to the project.
>> It's along the same lines as to why OpenCL by most vendors is developed privately..... (I realize this has gotten a lot more attention and better in the past 1-2 years)
> … you're absolutely right, that is a great analogy.  I think that the way OpenCL was developed, specifically its lack of open source engagement, is universally considered to be a failure that should not be repeated.  Look at all the vendors who independently had to invent the same functionality, then clashed when they each tried to merge it back to mainline clang.
> I'm not sure what business advantage you think that a fortran frontend would give you, but you should carefully consider what you think you're achieving.
Ok - thanks for that insightful heads up. It's not really Apples vs 
Apples though. OpenCL has multiple companies working on it, but for 
Fortran - who are "all the vendors"... (Fortran has been around *a lot* 
longer - it's not like new players are popping up every month)
In the past couple of years - I've been an advocate of a Fortran-clang 
front-end, but until recently it wasn't very active. No magic community 
formed and really who cares? (devils advocate hat on) Besides ANL - who 
will the potential users be? (Honest question to anyone reading this)

Google, Sony, Apple, Adobe???
On a more technical note - flang is not upstream friendly "right now" 
(imho). The technical issues with integrating it cleanly into clang 
upstream are and will be worked out. I think if we do move to an open 
development model we need to be working on clang master. This will get 
the project more exposure as well make it easier for people to test.

Fortran is totally non-c-family - It's like trying to add Python, Java 
or COBAL - It gets even more complicated with things like module 
formats, CAF and arrays. When we try to upstream our patches - who will 
review them? Will it be like OpenMP where things get bottlenecked 
waiting on reviews for (months/weeks). (This may tie into who will the 
users be and the overall general community interest)

The project has a great start, but to put things in the right 
perspective - this is month #4 for a project which could take 5, 10 or 
even 20 "engineering years" of effort.

Nothing is set in stone - this is a friendly discussion we're totally 
open to..

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