#857: Remove PARALLEL WORKSHARE

[hfp]

• Avoid nested parallelism (dbcsr_acc_set_active_device).
• Rely on omp_get_level (instead of omp_in_parallel),
  omp_in_parallel only accounts for active regions.
• Avoid IF-condition as part of the WORKSHARE-directive.
• Removed WORKSHARE construct from dbcsr_ptr_util,
• otherwise keep WORKSHARE if not in parallel region.
• There is potentially invalid nesting (parallel+X),
  e.g., nested in master or sections constructs.

[alazzaro]

Thanks @hfp I will take a look next week...

[hfp]

Thanks @hfp I will take a look next week...

Might be easier now (less work, only three files). I separated some cleanup work (#860).

[hfp]

@mkrack this single PR is apparently resolving all runtime issues with Intel Fortran Compiler (IFX) in CP2K/DBCSR. There is still the question why PARALLEL WORKSHARE DEFAULT(none) SHARED(...) IF(spawn) with spawn=.NOT. omp_in_parallel() does not work as opposed to the code shown here (but this might be well-covered by a bug report). Further, see #857 (comment) - it can be of interest for CP2K.

[hfp]

@alazzaro any feedback welcome - so far, no issues with this code on my side, I am actively using it since sending the PR.

[hfp]

Objective of this implementation is to exercise a way to preserve the (parallel) workshare. It does not judge (or confirms) whether the workshare is beneficial or not.

[alazzaro]

@hfp thanks, I will review everything next week and make a new RC that we can push to CP2K for more testings

[hfp]

Hold on merging this PR. I pulled in more expertise. I will reply on the original issue #857, and revise/close this PR accordingly.

[hfp]

The revised PR now drops the [PARALLEL] WORKSHARE constructs.