UltraMemV2: Memory Networks Scaling to 120B Parameters with Superior
  Long-Context Learning
Authors: name: Zihao Huang; name: Yu Bao; name: Qiyang Min; name: Siyan Chen; name: Ran Guo; name: Hongzhi Huang; name: Defa Zhu; name: Yutao Zeng; name: Banggu Wu; name: Xun Zhou; name: Siyuan Qiao
Published: 2025-08-26 07:33:11

Abstract: While Mixture of Experts (MoE) models achieve remarkable efficiency by
activating only subsets of parameters, they suffer from high memory access
costs during inference. Memory-layer architectures offer an appealing
alternative with very few memory access, but previous attempts like UltraMem
have only matched the performance of 2-expert MoE models, falling significantly
short of state-of-the-art 8-expert configurations. We present UltraMemV2, a
redesigned memory-layer architecture that closes this performance gap. Our
approach introduces five key improvements: integrating memory layers into every
transformer block, simplifying value expansion with single linear projections,
adopting FFN-based value processing from PEER, implementing principled
parameter initialization, and rebalancing memory-to-FFN computation ratios.
Through extensive evaluation, we demonstrate that UltraMemV2 achieves
performance parity with 8-expert MoE models under same computation and
parameters but significantly low memory access. Notably, UltraMemV2 shows
superior performance on memory-intensive tasks, with improvements of +1.6
points on long-context memorization, +6.2 points on multi-round memorization,
and +7.9 points on in-context learning. We validate our approach at scale with
models up to 2.5B activated parameters from 120B total parameters, and
establish that activation density has greater impact on performance than total
sparse parameter count. Our work brings memory-layer architectures to
performance parity with state-of-the-art MoE models, presenting a compelling
alternative for efficient sparse computation.