Hi Paul, Am 23.09.24 um 10:26 schrieb Paul Richard Thomas:
In addition to Andre's remarks, could you please tell us, when you resubmit, if this is a complete F2023 implementation of do concurrent. If not, what is missing?
Regarding missing parts: still to do is actually privatizing (with or without initialization) for variables that are listed with 'local' and 'local_init'. Hence, code doing that currently fails after doing all required diagnostic with a 'sorry not yet implemented error'. [My feeling is that doing it in trans*.cc might make most sense, but it could be also done by adding at Fortran AST level (inserting a BLOCK + adding the variable there).] Otherwise, all parsing + diagnostic should work; 'default(none)' is diagnostics only and 'shared' doesn't do anything, except affecting 'default(none)' diagnostic. — 'reduce' will have a code gen effect, but only when going to real concurrency/parallel execution. * * * If you talk about unimplemented 'do concurrent' features in general, gfortran does not handle the forall/do-concurrent header with typespec (i.e. 'do concurrent (integer :: i = 1, 4)', cf. https://gcc.gnu.org/PR96255 [F2018 feature]. * * * In terms of true parallelization: * I was (since a while) thinking of having a -fdo-concurrent=<serial|omp-parallel|omp-target-parallel|openacc> compile-time flag to handle this. * OpenMP 6.0 (added I think in Technical Report (TR) 13, which was released Aug 1, 2024) now supports '!$omp loop' on 'do concurrent' Either variant would then use the new locality spec (F2018/F2023 and new in gfortran) and hook into the existing OpenMP/OpenACC handling. – '!$omp loop' and -fdo-concurrent=omp-parallel are in any case easier than 'omp-target-parallel' as the latter will run into issues related to data mapping or (potentially) atomic updates now having to be in sync with host atomic access.
BTW Thanks for doing this. It was on my long term TODO list and is now struck off :-)
Yes – and I have heard from others that do-concurrent actually being concurrent – or at least having having the new locality specs even if not run concurrently is a much missed feature. — That might be from a small bubble, but still those users wand to have it. And also Damian mentioned that he has a project what will use it. Also thanks from my side! Tobias
