Oblique Projection Networks (OPN) Reference guide - variants, code, tests, complexity, and the application scope of oblique projections
Abstract
An operational reference on oblique projections in deep learning and their instantiation, Recursive Oblique Projection Networks (ROPN). It contains: (i) the geometric foundations; (ii) the five block variants with verified PyTorch code -Dense, Dense-fast, LoRA, Circulant, auto-ROPN; (iii) a quantitative illustration of Theorem 2 through a targeted test executed; (iv) the detailed anisotropy sweep; (v) a synthesis sheet (properties, complexity, measured timings); (vi) the detailed operation of auto-ROPN; and (vii) usage examples. Central message, supported by the tests: the oblique map is the right geometry on anisotropic data and outperforms any model structurally unable to exploit the covariance; a multilayer perceptron (MLP) recovers it on its own when the data allow.
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BibTeX
@misc{caspary2026oblique,
title = {{Oblique Projection Networks (OPN) Reference guide - variants, code, tests, complexity, and the application scope of oblique projections}},
author = {Olivier Caspary},
howpublished = {HAL},
year = {2026},
month = nov,
url = {https://hal.science/hal-05851796v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Oblique Projection Networks (OPN) Reference guide - variants, code, tests, complexity, and the application scope of oblique projections
AU - Olivier Caspary
PY - 2026
DA - 2026/11/04
PB - HAL
UR - https://hal.science/hal-05851796v1
AB - An operational reference on oblique projections in deep learning and their instantiation, Recursive Oblique Projection Networks (ROPN). It contains: (i) the geometric foundations; (ii) the five block variants with verified PyTorch code -Dense, Dense-fast, LoRA, Circulant, auto-ROPN; (iii) a quantitative illustration of Theorem 2 through a targeted test executed; (iv) the detailed anisotropy sweep; (v) a synthesis sheet (properties, complexity, measured timings); (vi) the detailed operation of auto-ROPN; and (vii) usage examples. Central message, supported by the tests: the oblique map is the right geometry on anisotropic data and outperforms any model structurally unable to exploit the covariance; a multilayer perceptron (MLP) recovers it on its own when the data allow.
ER -