A solver test failed in February and a hard-coded relaxation factor of 1.5 took the blame. Measured on every grid, 1.5 was within a sweep of the best on exactly one of them, February's failure had another cause, and the …
Five tests segfaulted on Linux and passed on Windows, on the same commit. The bug was a struct whose type quietly demanded an alignment malloc never promised — and the faulting instruction was not where the crash looked …
What computational fluid dynamics actually is — the history from Euler to WENO schemes, why analytical solutions and wind tunnels both hit walls, and where the hard parts lie.
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