Shuffling Cell Numbers Made LU-SGS 2.8× Slower — RCM Reordering and the Start Cell That Sets Sweep Direction
·8 min read
Shuffling cell numbers on a 576-cell grid pushed LU-SGS from 9 iterations to 25. RCM cuts bandwidth to 24, but the start corner still splits 9 from 21.
When Explicit Blows Up, Solve Implicit Without Inverting the Matrix — LU-SGS
·6 min read
Explicit CFL at 0.3 stalls for days. Backward Euler and two LU-SGS sweeps carry a Burgers shock through CFL 5 in 49 steps, with no full-matrix inverse.