DFA + residual-branch penalty test: seed=456, lam=0.01
  ep 0: ||h_L||=8.890e+00 ||g_2||=9.971e-04 acc=0.0928
  ep 1: ||h_L||=8.559e+02 ||g_2||=1.043e-05 eval_acc=0.3379 test_acc=0.3428
  ep 10: ||h_L||=7.817e+03 ||g_2||=2.220e-06 eval_acc=0.3594 test_acc=0.3539
  ep 20: ||h_L||=1.233e+04 ||g_2||=1.772e-06 eval_acc=0.3691 test_acc=0.3592
  ep 30: ||h_L||=1.320e+04 ||g_2||=1.691e-06 eval_acc=0.3691 test_acc=0.3604

FINAL test acc: 0.3604
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_s456.json
Saved results/dfa_pen_short/dfa_pen_lam0.01_s456.pt