ShallowWater: bugfix: fix h_star selection and limiter dpsi derivative - #378
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tamiko merged 1 commit intoSep 28, 2026
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compute_h_star() discarded the double rarefaction estimate h_star_left. The limiter's dpsi was missing a factor 2 and had the sign of the t term flipped. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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@tamiko Claude found 2 bugs with the shallow water solver. |
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| const auto dpsi_l = ScalarNumber(2.) * | ||
| (relax_small * (h_U + t_l * h_P) * h_P * v2_max - | ||
| ((q_U * q_P) + q_P * q_P * t_l)); | ||
| const auto dpsi_r = ScalarNumber(2.) * | ||
| (relax_small * (h_U + t_r * h_P) * h_P * v2_max - | ||
| ((q_U * q_P) + q_P * q_P * t_r)); |
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I am a little bit shocked that we got this one wrong.
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compute_h_star(): the second mask discarded the first one's result, soh_star_leftwas never used. Safe (overestimates lambda_max) but overly dissipative.dpsiwas missing a factor 2 and had the sign of the t term flipped.Updated test outputs: errors decrease by 10-20% for paraboloid and Ritter dam break. No bounds violations with
DEBUG_EXPENSIVE_BOUNDS_CHECK.The
paraboloid ... .output.gcc-13.3-avx2variant still has pre-fix numbers; I'll update it from CI.🤖 Generated with Claude Code