Re: Request for participation in GSoC

[Tobias Burnus <tobias@codesourcery.com>]

Hello,

welcome to the GCC/gfortran community.

On 08.03.23 14:02, Martin Jambor wrote:
> On Sat, Mar 04 2023, Priyabrata Mondal via Gcc wrote:
>> I want to
>> participate in Google Summer of Code 2023 by contributing to the *Fortran –
>> DO CONCURRENT* project, an implementation of loop that executes
>> concurrently. I have started to learn about parallel programming and
>> Fortran programming language.
>>               I have good knowledge of C, C++, Javascript, HTML, and CSS.
>>              can you suggest some resources so I can learn the technologies
>> that are required for this project?
>>               I will be highly grateful to you forever if you allow me to do
>> this project under your guidance.
> I assume you have read through
>    https://gcc.gnu.org/wiki/SummerOfCode#Before_you_apply
> have you managed to complete the steps outlined there?

I wrote the following the other day regarding 'do concurrent':

I think there are two parts to it: First, to add the changes of newer
Fortran to gfortran and then to actually use them to generate
concurrently running code. (Internally, gfortran currently handles 'do
concurrent' to run mostly like a normal loop – except that it annotates
the loops are independent. – Real parallelization would be useful, however.)

If you want to see examples, see do_concurrent_1.f90 to
do_concurrent_6.f90 in gfortran's testsuite, i.e.
gcc/testsuite/gfortran.dg/ in the GCC sources. That's at
https://gcc.gnu.org/git/?p=gcc.git;a=tree;f=gcc/testsuite/gfortran.dg;hb=refs/heads/master
/ But it is best to download GCC yourself via Git as described at
https://gcc.gnu.org/git.html

I want to note that the DO CONCURRENT syntax also permits a mask
argument, like in 'do concurrent (i=1:5, j=1:5, (i/=j))' where the last
argument selects a subset.

For the Fortran standard, see https://gcc.gnu.org/wiki/GFortranStandards

Fortran 2018 (= 18-007r1) adds for locality specifiers: LOCAL,
LOCAL_INIT, SHARED and DEFAULT(NONE).

Fortran 202x alias 2023 adds 'reduce' as in 'do concurrent (i = 1, n)
reduce(+:a, b, c) reduce(max:d, e, f)'

I think the first step is to add parsing support for those new features,
i.e. store them, check for issues (diagnostic) and then fail with a
'sorry not yet implemented'.

The next step would be to implement LOCAL/LOCAL_INIT for running on the
host.

And then, finally, would be to translate into code which can then be run
concurrently. I was thinking of mapping it internally to OpenMP or
OpenACC, to be toggled via a commandline option like
-fdo-concurrent=<openmp,openmp-target,openacc,...>.

* * *

And for getting started with GCC, I wrote:

I think the first step would be to download GCC and build it. Something
like "git clone" as described above, then "mkdir build" (some
directory); "cd build" and then "../configure --prefix=where-to-install"
followed by "make -j12" and "make install". The "-j12" runs 12 build
jobs in parallel. How much to use depends on your system.

You probably need to install some development versions of libraries such
as ISL, gmp, mpfr and mpc. If you don't have them readily, an option is
to run ./contrib/download_prerequisites to download those and build them
automatically alongside GCC.

I hope it helps to get started

Tobias

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