DFA + residual-branch penalty test: seed=123, lam=0.01
  ep 0: ||h_L||=8.791e+00 ||g_2||=9.848e-04 acc=0.0957
  ep 1: ||h_L||=8.047e+02 ||g_2||=1.064e-05 eval_acc=0.3320 test_acc=0.3279
  ep 10: ||h_L||=7.988e+03 ||g_2||=1.857e-06 eval_acc=0.3584 test_acc=0.3448
  ep 20: ||h_L||=1.251e+04 ||g_2||=1.450e-06 eval_acc=0.3633 test_acc=0.3597
  ep 30: ||h_L||=1.337e+04 ||g_2||=1.414e-06 eval_acc=0.3672 test_acc=0.3610

FINAL test acc: 0.3610
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_lam0.01_s123.json
Saved results/dfa_pen_short/dfa_pen_lam0.01_s123.pt