Near-identical neural net weights still diverge on ~3% of inputs after training

bravo_abad · x · 2026-11-08

Ly and Gong's study explains why deep learning is so sensitive to tiny changes: two networks starting from almost identical weights under the same deterministic training procedure still disagree on roughly 3% of inputs, and shrinking the initialization gap barely reduces this.

They trained VGG convolutional nets with SGD on handwritten digits (half the labels deliberately corrupted); prediction disagreement stayed near 2.9% as initialization differences varied across ten orders of magnitude.

The proposed explanation comes from dynamical systems: starting points leading to different outcomes are interwoven at extremely fine scales, with fractal-like phase portraits and a power-law fit supporting this geometry in a minimal network.

Original post →

More from Research

Research channel →