BITCOS squeezes ternary AI weights to 1.485 bits

BITCOS reaches 1.485 bits per weight on the sparsest of 29 tested models, Evangelos Georganas, Alexander Heinecke and Pradeep Dubey report in a 14 September preprint. The presence-bitmap plus sign-vector layout records which ternary {-1,0,+1} weights are nonzero separately from their signs, under the log2(3) ≈1.585 reference and 1.625-bit five-trit packing.