Resolve "Several fixes for RK3, including tiling when using AGRIF"

Closes #417 (closed).

Tests

Regular checks

• Can this change be shown to produce expected impact (option activated)?
• Can this change be shown to have a null impact (option not activated)?
• Results of the required bit comparability tests been run: are there no differences when activating the development?

  • If some differences appear, is reason for the change valid/understood?

    AGRIF_DEMO and VORTEX results change with respect to the previous commit, with and without tiling. In the case without tiling, this is due to changes to the cosmetic zeroing of ww on AGRIF child zooms in wzv (issue 3 in "AGRIF issues" in #417 (closed)).

  • If some differences appear, is the impact as expected on model configurations?

• Is this change expected to preserve all diagnostics?
  • If no, is reason for the change valid/understood?
• Are there significant changes in run time/memory?

Other testing

Other testing was performed using 2-month runs of ORCA2_ICE_PISCES with passive tracers and SI3 turned off, with MLF and RK3 timestepping, and using many different namelist parameter settings and CPP keys. Only z partial steps (zps) vertical coordinates were tested.

The testing checked for restartability, tiling reproducibility (whether using tiling changes the results) and preservation of results with respect to the main. This was done by comparing the contents of run.stat files, as well as data from most available model diagnostics and from restart files.

Review

A successful review is needed to schedule the merge of this development into the future NEMO release during next Merge Party (usually in November).

Assessments

• Is the proposed methodology now implemented?
• Are the code changes in agreement with the flowchart defined at preview step?
• Are the code changes in agreement with list of routines and variables as proposed at preview step?
  • If, not, are the discrepancies acceptable?
• Is the in-line documentation accurate and sufficient?
• Do the code changes comply with NEMO coding standards?
• Is the development documented with sufficient details for others to understand the impact of the change?
• Is the project doc (manual, guide, web, ...) now updated or completed following the proposed summary in preview section?