Add Manager Class for Region Level Summary Variables

[bska]

This PR introduces a new manager-style class

RegionVariableCollection

which aggregates region set descriptors and variable values and distributes per-cell variable contributions to all pertinent region sets. Client code is expected to create a single object of this class and initialise it with a populated region variable mapping. Then as needed, typically at the end of every converged time step, client code is expected to perform a value accumulation as follows:

1. Prepare this object for accumulation (prepareValueAccumulation())
2. For each applicable variable and cell, include the per-cell contribution (addCellValue()).
3. Commit those contributions to compute the new variable values (commitValues()).

Once commitValues() has completed, client code may retrieve those new variable values through the regionVariableValues() member function. The process of committing values may involve cross-rank MPI communication in parallel and will add to or overwrite the current values depending on whether the variable is declared cumulative.

We also include two helper functions,

• regionSetIndex()
• variableIndex()

which essentially just forward a query to the variable mapping object supplied as an argument. The one exception is that regionSetIndex() knows that "FIELD" is a special region set pertaining to field-level quantities and will act accordingly.

[bska]

I'm creating this PR in draft mode because it depends on, and contains, the earlier PR #5277. I will keep the PR in a draft state until such time as it is ready for review and merging.

[bska]

jenkins build this please

[Copilot]

Pull request overview

This PR adds a new Opm::RegionVariableCollection manager that owns region-set descriptors and value storage, and provides a simple accumulation workflow for region-level summary variables (including special handling for the FIELD “region set”).

Changes:

• Introduces RegionVariableCollection with initialise(), prepareValueAccumulation(), per-cell accumulation via addCellValue(), and commitValues().
• Adds helper lookups regionSetIndex() and variableIndex() to bridge mapping names to numeric indices (with FIELD handled specially).
• Wires the new implementation into the build and adds a dedicated unit test suite.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 6 comments.

File	Description
opm/output/eclipse/RegionVariableCollection.hpp	Declares the new manager API and its documentation.
opm/output/eclipse/RegionVariableCollection.cpp	Implements region descriptor/value initialization and per-cell accumulation logic.
tests/test_region_variable_collection.cpp	Adds unit tests covering non-cumulative/cumulative behavior across region sets and variables.
CMakeLists_files.cmake	Registers the new source, public header, and test in the build.

Suppressed comments (1)

opm/output/eclipse/RegionVariableCollection.hpp:141

• The documentation refers to addRegionValue(), but callers will be using addCellValue() on this class. This should be updated to avoid confusion.

        /// Adds increment values for cumulative quantities and overwrites
        /// current values for non-cumulative quantities.
        ///
        /// Must be called after the last call to addRegionValue().
        void commitValues();

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[bska]

I have addressed Copilot's initial review comments and the PR goes through a build check. I'm marking this PR as "ready for review" now.

[bska]

jenkins build this please

[bska]

jenkins build this please

[akva2]

LGTM

[bska]

jenkins build this please

[bska]

PR approved and build check is green. I'll merge into master.