Fix MLMG: adjust face Dirichlet values to match HYPRE cell-centre BCs#240
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jameslehoux merged 1 commit intoworkingfrom Apr 1, 2026
Merged
Fix MLMG: adjust face Dirichlet values to match HYPRE cell-centre BCs#240jameslehoux merged 1 commit intoworkingfrom
jameslehoux merged 1 commit intoworkingfrom
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The previous approach of pinning boundary cells after the solve broke flux conservation. Instead, extend the Dirichlet face values outward by half a cell so the resulting cell-centre solution at the boundary cells matches HYPRE's convention (vlo at cell 0, vhi at cell N-1). For an N-cell domain: face_lo = vlo - 0.5 * (vhi - vlo) / (N - 1) face_hi = vhi + 0.5 * (vhi - vlo) / (N - 1) This produces tau = (N-1)/N for a uniform block, consistent with HYPRE and the analytical benchmark expectation. https://claude.ai/code/session_01RKnn97qiD7sbCeABHH3eQk
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The previous approach of pinning boundary cells after the solve broke flux conservation. Instead, extend the Dirichlet face values outward by half a cell so the resulting cell-centre solution at the boundary cells matches HYPRE's convention (vlo at cell 0, vhi at cell N-1).
For an N-cell domain:
face_lo = vlo - 0.5 * (vhi - vlo) / (N - 1)
face_hi = vhi + 0.5 * (vhi - vlo) / (N - 1)
This produces tau = (N-1)/N for a uniform block, consistent with HYPRE and the analytical benchmark expectation.