processEclipseFormat: merge removed cells on edge-conformal grids

[hnil]

An edge-conformal grid has to stay topologically connected. Cells removed by MINPV must therefore be merged geometrically rather than bridged with NNCs, which would create faces with no geometric counterpart — vertex-based discretizations cannot use those.

So for edge_conformal grids this selects mergeMinPVCells, asserts that no MINPV, PINCH or explicit NNC survives, and treats the merged columns as active gaps.

Nothing changes unless edge_conformal is set.

Split out of #1058 so it can be reviewed on its own: that PR also adds an opt-in thin-cell mode to MinpvProcessor, which is a separate question and not needed for ordinary grids. #1058 is now stacked on this one.

[bska]

jenkins build this please

[Copilot]

Pull request overview

This PR updates CPGrid Eclipse-format processing to support edge-conformal grids by merging MINPV-removed cells geometrically (instead of bridging via NNCs), and by enforcing that edge-conformal grids do not rely on PINCH or explicit NNC connections that would create non-geometric faces.

Changes:

• Wire edge_conformal to enable geometric merging of MINPV-removed cells via MinpvProcessor (mergeMinPVCells).
• Add edge-conformal invariants intended to ensure no MINPV/PINCH/explicit NNC bridging remains.
• Treat merged columns as active gaps by forcing pinchActive during grid construction when edge_conformal is enabled.

Suppressed comments (3)

opm/grid/cpgrid/processEclipseFormat.cpp:216

• When edge_conformal is enabled, mergeMinPVCells avoids MINPV NNCs, so minpv_result.nnc can be empty even though MinpvProcessor::process() still modified zcornData (collapsed/merged cells). Guarding this->zcorn = zcornData; only on minpv_result.nnc risks losing the updated ZCORN needed for correct EclipseGrid output.

This issue also appears in the following locations of the same file:

• line 230
• line 431

                                          poreVolume, ecl_grid.getMinpvVector(), actnumData, mergeMinPVCells,
                                          zcornData.data(), nogap, pinchOptionALL,
                                          permZ, multZ, tolerance_unique_points);
                if (!minpv_result.nnc.empty()) {
                    this->zcorn = zcornData;

opm/grid/cpgrid/processEclipseFormat.cpp:234

• This assert(minpv_result.nnc.empty()) is a release-build no-op, so an edge_conformal grid could silently proceed while still having MINPV/PINCH NNCs (MinpvProcessor can also generate NNCs for vertical gaps unrelated to MINPV). If edge_conformal requires no NNCs, enforce it with a runtime check and a clear error message.

            if (edge_conformal) {
                // Merged (not bridged) cells: an edge-conformal grid must not
                // produce artificial faces via MINPV NNCs.
                assert(minpv_result.nnc.empty());
            }

opm/grid/cpgrid/processEclipseFormat.cpp:435

• These assert()s are compiled out in release builds, so edge_conformal grids could still be built with PINCH or explicit NNCs even though the comment states they must not. Convert the invariant into a runtime check so invalid decks/configurations fail deterministically with an actionable message.

                // the merged columns as active gaps.
                pinchActive_copy = true;
                assert(nnc_cells[PinchNNC].empty());
                assert(nnc_cells[ExplicitNNC].empty());
            }

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[bska]

Very good. I'll merge into master.