2.3 KiB
Larger Krylov window
This branch changes only the sandbox example's existing FGMRES restart setting from 40 to 160. It adds no public API and does not change the general backend default. The warm-start safeguard is a separate hypothesis and branch.
Matched evidence
The common diagnostic executable at commit 9bd4af6 ran n=1, K=2/pi, M=1,
J=0.05, with no central-density constraint, on the unchanged sandbox.smesh.
Both runs used nonlinear rtol=1e-8, atol=0, linear tolerance=0.03, and at most
200 linear iterations. Only the restart window differed.
| Result | Restart 40 | Restart 160 |
|---|---|---|
| Accepted full Newton steps | 5 | 7 |
| Final normalized residual | 6.03609e-9 | 3.38036e-11 |
| Strict convergence | No: sixth linear solve fails | Yes |
| Total linear iterations, including failed attempt | 370 | 292 |
| Largest final virial error among four definitions, q=14/18 | 3.73183e-7 | 3.73466e-7 |
The first four steps coincide exactly. The larger window first changes the fifth linear solve. This is live nonlinear evidence, supplemented by the earlier frozen-system comparisons. Single wall-time samples (291 versus 272 seconds, including physical diagnostics) do not establish a general speedup.
Limits and validation
The larger window requires more Krylov storage. It is a useful example setting, not a universal default: n=1.5 without the central constraint still stalls with this window, and eventually fails a linear gate. The n=3 frozen control also needs a stronger numerical treatment. This change does not establish a fraction of critical rotation and does not alter the convergence or virial tolerances.
Removing the n=1 example's central-density constraint is independently supported
on research/central-constraint-20260916; combine the two changes for the intended
example. The combined sandbox compiles at b3a752b. Its nonrotating physical
counterpart in the diagnostic at c88baa1 reaches strict convergence in six
full steps, with F=1.65157e-13 and all eight q14/q18 virial checks below
3.731e-7. The diagnostic uses its recorded stopping controls; this is not a
claim that the literal sandbox executable was used for the physical measurements.
Raw results and exact build/mesh/executable provenance are retained in the
workspace's diagnostics/numerical_campaign_2026-09-16/controls directory.