DFA + residual-branch penalty test: seed=456, lam=0.0001
  ep 0: ||h_L||=8.890e+00 ||g_2||=9.971e-04 acc=0.0928
  ep 1: ||h_L||=3.954e+03 ||g_2||=2.489e-06 eval_acc=0.2988 test_acc=0.3043
  ep 10: ||h_L||=1.636e+04 ||g_2||=8.429e-07 eval_acc=0.3506 test_acc=0.3490
  ep 20: ||h_L||=2.166e+04 ||g_2||=7.285e-07 eval_acc=0.3721 test_acc=0.3601
  ep 30: ||h_L||=2.285e+04 ||g_2||=7.001e-07 eval_acc=0.3711 test_acc=0.3597

FINAL test acc: 0.3597
Compare to:
  DFA-vanilla (3-seed mean):    0.308
  DFA-shallow (3-seed mean):    0.349
  DFA-frozen (3-seed mean):     0.349
  BP-trainable (3-seed mean):   0.609
Saved results/dfa_pen_short/dfa_pen_lam0.0001_s456.json
Saved results/dfa_pen_short/dfa_pen_lam0.0001_s456.pt