Learnable Weighted Superposition in HDC and its Application to Multi-channel Time Series ClassificationShow others and affiliations
2024 (English)In: 2024 International Joint Conference on Neural Networks (IJCNN), IEEE, 2024Conference paper, Published paper (Refereed)
Abstract [en]
The vector superposition operation plays a central role in Hyperdimensional Computing (HDC), enabling compositionality of hypervectors without expanding the dimensionality, unlike concatenation. However, a problem arises when the quantity of superimposed vectors surpasses a certain threshold, which is determined by the hypervector’s information capacity relative to its dimensionality. Beyond this point, cross-talk noise incrementally obscures the distinctiveness of individual hypervectors and information is lost. To solve this challenge, we introduce a novel method for weighting individual hypervectors within the superposition, ensuring that only those hypervectors crucial for a given task are prioritized. The weights are learned end-to-end using the backpropagation algorithm in a neural network. Our method is characterized by two key features: (1) The resultant weighting model is exceptionally compact, as the number of trainable weights is equal to the total number of hypervectors in the superposition; (2) The model offers enhanced explainability due to the compositional nature of its encoding. These features collectively contribute to the efficiency and effectiveness of our proposed classification approach using hyperdimensional computing. We illustrate our approach through the multi-channel time series classification task. In this framework, each channel is encoded as a hypervector-descriptor, and those are subsequently composed into a single hypervector via superposition. This superimposed vector forms the basis for training the classification model based on the neural network. Applying our approach of weighted superposition on this task improved the classification performance compared to standard superposition or concatenation of feature vectors, especially for larger numbers of channels.
Place, publisher, year, edition, pages
IEEE, 2024.
Keywords [en]
HDC/VSA, neural networks, superposition, weighted superposition, bundling
National Category
Computer Sciences Computer Systems
Research subject
Dependable Communication and Computation Systems
Identifiers
URN: urn:nbn:se:ltu:diva-110295DOI: 10.1109/IJCNN60899.2024.10650604ISI: 001315691505103Scopus ID: 2-s2.0-85204954431OAI: oai:DiVA.org:ltu-110295DiVA, id: diva2:1904782
Conference
13th IEEE World Congress on Computational Intelligence (WCCI 2024), Yokohama, Japan, June 30 - July 5, 2024
Note
Funder: German Federal Ministry for Economic Affairs and Climate Action; Swedish Foundation for Strategic Research (UKR22-0024, UKR24-0014); Swedish Research Council (VR SAR grant no.GU 2022/1963); LTU support grant; Swedish Research Council (VR grant no. 2022-04657);
ISBN for host publication: 978-8-3503-5931-2;
2024-10-102024-10-102025-10-21Bibliographically approved