Weave Mamba Fusion: Global Cross-Scale Interaction for Lightweight Face Detection
Authors & Institutions
Dohun Kim
School of Data Science, The University of Suwon
Jinmyung Jung
School of Data Science, The University of Suwon
What Problem It Solves
WeaveFace aims to add global cross-scale interaction to a sub-million-parameter face detector without paying the memory and compute cost of concatenating complete feature maps or applying quadratic self-attention.
Key Result
On WIDER FACE, WeaveFace reports 91.41% mean AP with 0.34 million parameters and 1.16 GFLOPs. Its Hard-subset AP is 87.14%, the area where small and occluded faces most stress the cross-scale design. The paper reports stronger accuracy than prior detectors below 0.5 million parameters.
Abstract
Feature pyramid methods, from FPN to BiFPN, have achieved strong performance in face detection by fusing multi-scale features. However, detecting faces under unconstrained conditions, such as small scale, occlusion, and extreme pose, remains difficult, as it requires global cross-scale dependencies that local fusion cannot model. State space models such as Mamba provide global context with linear complexity by scanning features as a sequence, and therefore offer a promising direction for this problem. Nevertheless, such a scan needs the two pyramid scales combined into a single feature map, and the way they are combined determines whether cross-scale structure is preserved. Summation collapses the two scales before the scan, so the scan has no cross-scale structure to exploit, while concatenation keeps both scales but at far higher cost. To address this, we propose Weave Mamba Fusion (WMF), which interleaves two adjacent pyramid scales column by column so that each step of a horizontal bidirectional SS2D scan moves from one scale to the other. With partial-channel processing and parameter-free de-weaving, WMF enables efficient cross-scale interaction while preserving feature structure. Integrating WMF into every fusion node yields WeaveBiFPN, the neck of our WeaveFace detector. On WIDER FACE, WeaveFace achieves 91.41% mean AP with only 0.34M parameters and 1.16 GFLOPs, outperforming prior detectors under 0.5M parameters. Its largest gains are on the Hard subset, where it reaches 87.14% AP. The code is publicly available at https://github.com/dohun-mat/WeaveMambaFusion.
Research Starting Point
Small, occluded, and strongly rotated faces need fine spatial detail from high-resolution pyramid levels and semantic context from low-resolution levels. Standard FPN and BiFPN fusion is local, while full attention can be too expensive at the resolutions used by a lightweight detector.
Method
Weave Mamba Fusion interleaves columns from adjacent pyramid levels so a bidirectional horizontal SS2D scan alternates between scales at each step. Only part of the channels are processed, and a parameter-free de-weaving operation restores the original scales. Replacing each BiFPN fusion node with this operator produces WeaveBiFPN, which is used as the neck of the WeaveFace detector.
Paper Summary
This is a promising detector for edge deployments where parameter count and FLOPs matter, particularly when tiny faces dominate. Teams should still measure wall-clock latency and memory on their own accelerator because the paper's main efficiency evidence is model complexity.