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Thomas Blum
34d8d003a8
Smoother shift: - Replace hard-coded mass^2 = 0.0025 with fine_lambda_max / divisor, measured at runtime via PowerMethod on the SchurStaggeredOperator. - Current divisor = 200 (tunable); concentrates the O(8) CG polynomial zeros on the high-frequency end of the spectrum [shift, lambda_max], repairing the spectral leakage introduced at coarse-cell boundaries when the coarse-grid solution is promoted back to the fine grid. - Add explanatory comment on the lego-block edge / covariant-derivative physics behind the high-mode smoothing requirement. Chebyshev filter (IRL): - Fix lambda_lo = 0.02 (was mass^2 * 0.5 = 0.00125). Tuning history logged in comments: lo=0.005 → 0/24 modes (T_70~53); lo=0.01 → 24/24 but 2 restarts; lo=0.02 → 24/24 in 1 restart. - Reduce Nk/Nm from 48/96 to 24/48 (target 24 near-null modes only). - Print Chebyshev filter parameters at run time. CG baseline: - Add sequential single-RHS CG loop before the HDCG solve to establish unpreconditioned iteration count and wall time for direct comparison. ImplicitlyRestartedBlockLanczosCoarse: - Print Ritz values before and after implicit shift at each restart. - Print alpha/beta block-diagonal elements at each Lanczos step. Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>