c499f7f2b0
Benchmark on `2humanoid100.xml` (nefc=1785, nv=654): ``` Convergence at fixed iteration count (mean relative error vs Newton): 20 iters: 2.98e-03 vs 1.54e-02 (5.2x better) 40 iters: 8.14e-05 vs 2.60e-03 (32x better) 80 iters: 1.17e-07 vs 1.77e-04 (1500x better) Pipeline throughput (tolerance=1e-8, islands disabled): Nesterov: 243 steps/s, 46 iters/step Baseline: 151 steps/s, 95 iters/step Solver speedup: 1.8x, overall step speedup: 1.6x Pipeline throughput (tolerance=1e-8, islands enabled): Nesterov: 306 steps/s, 442 iters/step Baseline: 175 steps/s, 966 iters/step Solver speedup: 2.1x, overall step speedup: 1.7x ``` PiperOrigin-RevId: 936610759 Change-Id: I2978e8bd545971d9151005623967e5cf0ad125cc