Allow to ignore specific dimensions in "shift to zero indexing"

[MichaelSt98]

allow to ignore specific dimensions ...

[github-actions]

Documentation for this branch can be viewed at https://sites.ecmwf.int/docs/loki/236/index.html

[codecov]

Codecov Report

Attention: Patch coverage is 93.59244% with 61 lines in your changes are missing coverage. Please review.

Project coverage is 92.71%. Comparing base (970e0b6) to head (1dc82a6).
Report is 53 commits behind head on main.

Files	Patch %	Lines
loki/bulk/item.py	92.44%	34 Missing ⚠️
loki/bulk/scheduler.py	95.48%	12 Missing ⚠️
loki/bulk/configure.py	90.52%	9 Missing ⚠️
loki/program_unit.py	81.81%	2 Missing ⚠️
loki/transform/build_system_transform.py	33.33%	2 Missing ⚠️
loki/sourcefile.py	83.33%	1 Missing ⚠️
transformations/transformations/data_offload.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
+ Coverage   92.47%   92.71%   +0.23%     
==========================================
  Files          95       95              
  Lines       17473    17828     +355     
==========================================
+ Hits        16159    16529     +370     
+ Misses       1314     1299      -15     

Flag	Coverage Δ
lint_rules	96.22% <ø> (ø)
loki	92.71% <93.57%> (+0.27%)	⬆️
transformations	91.94% <94.44%> (-0.05%)	⬇️

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[reuterbal]

Thanks, looks good. I've left two remarks about implementation and I think the docstring could be slightly improved maybe.

[reuterbal]

Just to propose a slightly streamlined alternative to avoid the explicit loop:

Suggested change

	shift = True
	for var in FindVariables().visit(d):
	if var in ignore:
	shift = False
	if shift:
	new_dims += [d - sym.Literal(1)]
	else:
	new_dims += [d]
	if ignore and any(var in ignore for var in FindVariables().visit(d)):
	new_dims += [d]
	else:
	new_dims += [d - sym.Literal(1)]

[reuterbal]

It's generally preferred to assign None as default value for optional arguments, and then convert it to a tuple in the function body, e.g. ignore = as_tuple(ignore).
That also adds the benefit that you can do something like shift_to_zero_indexing(routine, ignore='myvar') and wouldn't get the unexpected behaviour that this is treated as ignore=('m', 'y', 'v', 'a', 'r').

[reuterbal]

Maybe something like this would be more descriptive?

Suggested change

	Dimensions (or rather variables being dimensions) to be ignored
	List of variable names for which, if found in the dimension expression of an array subscript, that dimension is not shifted to zero.

[reuterbal]

Thanks for addressing the comments, all good now!

[mlange05]

Looks good. Many thanks for you patience. GTG