|
BP + lam=1e-2 ||f||^2 penalty trained for 30 epochs (s42):
ep 30 final: test_acc 0.5303
margin vs DFA-shallow 0.349: +18.13 pp
The 2x2 accuracy grid:
no penalty with penalty
BP 0.609 0.530
DFA 0.308 0.363
Penalty effect on BP: -8 pp (capacity regularization cost)
Penalty effect on DFA: +5.5 pp (rescue from active harm)
Mode 2 (intrinsic credit quality) is confirmed REAL by this control:
even after the penalty's capacity cost, BP achieves +18 pp depth
utilization. DFA under the same penalty achieves only +1.4 pp. The
difference (~17 pp) cannot be attributed to capacity loss — it is
genuine credit-quality cost of random feedback vs true backprop
gradient.
This validates the round 19 'two distinct failure modes' framing:
mode 2 is not a penalty-induced regularization artifact.
|
