- 1. High-degree polynomial expansions 20th June 2022 High-degree polynomial expansions 20th June 2022 1 / 100
- 2. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 2 / 100
- 3. High-degree polynomial expansions 20th June 2022 3 / 100
- 4. Imagenet https: // paperswithcode. com/ sota/ image-classification-on-imagenet High-degree polynomial expansions 20th June 2022 4 / 100
- 5. Deep-learning architectures K. He, X. Zhang, X., S. Ren, J. Sun, Deep residual learning for image recognition. In Proceedings of the IEEE conference on computer vision and pattern recognition (CVPR), 2016 High-degree polynomial expansions 20th June 2022 5 / 100
- 6. Deep-learning architectures (a) (b) J Hu, L Shen, G Sun. ’Squeeze-and-excitation networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2018. X. Wang, R. Girshick, A. Gupta, K. He. ’Non-local Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2018. High-degree polynomial expansions 20th June 2022 6 / 100
- 7. MLP layer High-degree polynomial expansions 20th June 2022 7 / 100
- 8. MLP layer High-degree polynomial expansions 20th June 2022 8 / 100
- 9. Squeeze-and-Excitation Nets are 2nd degree polynomials High-degree polynomial expansions 20th June 2022 9 / 100
- 10. Squeeze-and-Excitation Nets are 2nd degree polynomials High-degree polynomial expansions 20th June 2022 10 / 100
- 11. Non-local neural network is a 3rd degree polynomial High-degree polynomial expansions 20th June 2022 11 / 100
- 12. Non-local neural network is a 3rd degree polynomial High-degree polynomial expansions 20th June 2022 12 / 100
- 13. Self-Attention is a 3rd degree polynomial High-degree polynomial expansions 20th June 2022 13 / 100
- 14. Learning with polynomials, an old idea Mapping Units [Hinton, 1985], ”dynamic mapping” [v.d. Malsburg; 1981] Binocular+Motion Energy models [Adelson, Bergen; 1985], [Ozhawa, DeAngelis, Freeman; 1990], [Fleet et al., 1994]. Sigma-Pi neural unit [Mel, Koch; 1990]. Higher Order Botlzmann Machines / Higher Order Neural Networks [Sejnowski; 1986]. Subspace SOM [Kohonen; 1996], topographic ICA [Hyvarinen, Hoyer; 2000] [Karklin, Lewicki;2003]. Bilinear Models [Tenebaum and Freeman; 2008], [Ohlshaussen; 1994], [Grimes, Rao; 2005]. Higher Order Restricted Boltzmann Machines (RBMs) [Memisevic and Hinton; 2007], [Ranzato et al; 2010]. Gating mechanisms; LSTM [Hochreiter, Schmidhuber 1997], Multiplicative RNN [Sutskever, Martens, Hinton; 2011]. High-degree polynomial expansions 20th June 2022 14 / 100
- 15. Group Method of Data Handling (GMDH) One of the first approaches of systematic design of nonlinear relationships. Generation of Partial Descriptions of data (PDs) with two input variables. Shortcoming: tends to produce an overly complex network. A Ivakhnenko. ‘Polynomial theory of complex systems.’ IEEE Transactions on Systems, Man, and Cybernetics, 1971. High-degree polynomial expansions 20th June 2022 15 / 100
- 16. Mapping Units / Higher Order Boltzmann Machines Hinton et al. (1985) and Sutskever et al. (2011) argue that multiplications (mapping units) allow for better modeling of conjunctions. Higher order Boltzmann Machines and Higher order RBMs utilize multiplication in factorized representations, e.g., bilinear models factorize style and content. High-degree polynomial expansions 20th June 2022 16 / 100
- 17. Pi-Sigma network (PSN) Single hidden layer learns multiple affine transformations of the data, multiplies them to obtain the output. hji = X k wkji xk + θji yi = σ( Y j hji ) . Y Shin, J Ghosh. ‘The pi-sigma network: an efficient higher-order neural network for pattern classification and function approximation.’ International Joint Conference on Neural Networks, 1991. High-degree polynomial expansions 20th June 2022 17 / 100
- 18. Sigma-Pi-Sigma Neural Network (SPSNN) Composed of different orders of pi-sigma networks. fSPSNN = k X i=1 fPSNk = k X i=1 k Y j=1 hjk . C Li. ‘A sigma-pi-sigma neural network (SPSNN).’ Neural Processing Letters, 2003. High-degree polynomial expansions 20th June 2022 18 / 100
- 19. Factorization Machines Second degree polynomial net to combine the features under sparse data. The weight matrix is mapped into a low-rank space using matrix factorization. ŷ(x) := w0 + n X i=1 wi xi + n X i=1 n X j=i+1 ⟨vi , vj⟩ xi xj , where the learnable parameters are: w0 ∈ R, w ∈ Rn and V ∈ Rn×k (k ≫ n). S Rendle. ‘Factorization Machines.’ International Conference on Data Mining, 2010. High-degree polynomial expansions 20th June 2022 19 / 100
- 20. Variations of Factorization Machines Field-aware FM (FFM): Different vectors are used when the features of different fields combination. ŷ(x) := w0 + n X i=1 wi xi + n X i=1 n X j=i+1 D vi,fj , vj,fi E xi xj . Field-weighted FM: Add a weight parameter for every two features. ŷ(x) := w0 + n X i=1 wi xi + n X i=1 n X j=i+1 ⟨vi , vj⟩ xi xjrfi ,fj . Higher-order FM: Third-order or higher-order feature combination problems. Y Juan, Y Zhuang, W Chin, C Lin. ‘Field-aware factorization machines for CTR prediction.’ In ACM conference on recommender systems, 2016. J Pan, et al. ‘Field-weighted factorization machines for click-through rate prediction in display advertising.’ In World Wide Web Conference, 2018. M Blondel, A Fujino, N Ueda, M Ishihata. ‘Higher-order factorization machines.’ In Advances in neural information processing systems (NeurIPS), 2016. High-degree polynomial expansions 20th June 2022 20 / 100
- 21. Multiplicative Recurrent Neural Networks (MRNN) Character-level language modeling tasks. Multiplicative (or “gated”) connections. factor state sequence ft = diag(Wfx xt) · Wfhht−1 hidden state sequence ht = tanh(Whf ft + Whx xt) output sequence ot = Wohht + bo . I Sutskever, J Martens, G Hinton. ‘Generating text with recurrent neural networks.’ In International Conference on Machine Learning (ICML), 2011. High-degree polynomial expansions 20th June 2022 21 / 100
- 22. Sum-Product Networks (SPN) H Poon, P Domingos. ‘Sum-product networks: A new deep architecture.’ In International Conference on Computer Vision Workshops, 2011. High-degree polynomial expansions 20th June 2022 22 / 100
- 23. Multiplicative interactions High-degree polynomial expansions 20th June 2022 23 / 100
- 24. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 24 / 100
- 25. Outline 1 Introduction 2 Higher-degree polynomial expansions Notation 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 25 / 100
- 26. Formalism In Machine Learning tasks, we have (at least) one input and one output. The goal is to learn G(z) : Rd → Ro with z ∈ Rd the input. Neural networks use a composition of linear and unitary non-linear units. We augment this structure and we capture the higher-order correlations using tensors. High-degree polynomial expansions 20th June 2022 26 / 100
- 27. Hadamard product Let matrices Γ ∈ R2×3 and P ∈ R2×3. The Hadamard product Γ ∗ P is denoted as ‘∗’ and defined as: " γ(1,1) γ(1,2) γ(1,3) γ(2,1) γ(2,2) γ(2,3) # | {z } Γ ∗ " ρ(1,1) ρ(1,2) ρ(1,3) ρ(2,1) ρ(2,2) ρ(2,3) # | {z } P = " γ(1,1)ρ(1,1) γ(1,2)ρ(1,2) γ(1,3)ρ(1,3) γ(1,1)ρ(2,1) γ(1,2)ρ(2,2) γ(1,3)ρ(2,3) # | {z } Γ∗P (1) The Hadamard product of Γ ∈ RI×N and P ∈ RI×N results in a matrix of dimensions I × N. Hadamard, J. ’Leçons sur la Propagation des Ondes et les Équations de l’Hydrodynamique’, 1903. Halmos, Paul R. ’Finite-dimensional vector spaces’, Annals of Mathematics Studies, Princeton University Press, 1948. High-degree polynomial expansions 20th June 2022 27 / 100
- 28. Khatri-Rao product Let matrices Γ ∈ R2×3 and P ∈ R3×3. The Khatri-Rao product Γ ⊙ P is denoted as ‘⊙’ and defined as: " γ(1,1) γ(1,2) γ(1,3) γ(2,1) γ(2,2) γ(2,3) # | {z } Γ ⊙ ρ(1,1) ρ(1,2) ρ(1,3) ρ(2,1) ρ(2,2) ρ(2,3) ρ(3,1) ρ(3,2) ρ(3,3) | {z } P = γ(1,1)ρ(1,1) γ(1,2)ρ(1,2) γ(1,3)ρ(1,3) γ(1,1)ρ(2,1) γ(1,2)ρ(2,2) γ(1,3)ρ(2,3) γ(1,1)ρ(3,1) γ(1,2)ρ(3,2) γ(1,3)ρ(3,3) γ(2,1)ρ(1,1) γ(2,2)ρ(1,2) γ(2,3)ρ(1,3) γ(2,1)ρ(2,1) γ(2,2)ρ(2,2) γ(2,3)ρ(2,3) γ(2,1)ρ(3,1) γ(2,2)ρ(3,2) γ(2,3)ρ(3,3) | {z } Γ⊙P (2) The Khatri-Rao product of Γ ∈ RI×N and P ∈ RJ×N results in a matrix of dimensions (IJ) × N. Khatri, C. G., and C. Radhakrishna Rao. ’Solutions to some functional equations and their applications to characterization of probability distributions.’ Sankhyā: the Indian journal of statistics, series A (1968): 167-180. High-degree polynomial expansions 20th June 2022 28 / 100
- 29. Tensors Tensors → multi-dimensional arrays. High-degree polynomial expansions 20th June 2022 29 / 100
- 30. Tensors Tensors → multi-dimensional arrays. The order is the number of dimensions, e.g. X ∈ R4×4×4 has order 3. High-degree polynomial expansions 20th June 2022 29 / 100
- 31. Tensors Tensors → multi-dimensional arrays. The order is the number of dimensions, e.g. X ∈ R4×4×4 has order 3. Third-order tensor illustration: 𝑥𝑖 𝑥𝑗 𝑥𝑘 High-degree polynomial expansions 20th June 2022 29 / 100
- 32. Tensors Tensors → multi-dimensional arrays. The order is the number of dimensions, e.g. X ∈ R4×4×4 has order 3. Third-order tensor illustration: 𝑥𝑖 𝑥𝑗 𝑥𝑘 Let W ∈ RI1×···×IM and u ∈ RIm with m ∈ [1, . . . , M]. The mode-m vector product W ×m u is: (W ×m u)i1,...,im−1,im+1,...,iM = Im X im=1 wi1,...,iM uim (3) High-degree polynomial expansions 20th June 2022 29 / 100
- 33. CP decomposition Goal: Decompose a tensor W to a sequence of low-rank components. High-degree polynomial expansions 20th June 2022 30 / 100
- 34. CP decomposition Goal: Decompose a tensor W to a sequence of low-rank components. In matrix form: W(1) . = U[1] J2 m=M U[m] T where {U[m]}M m=1 are the factor matrices. High-degree polynomial expansions 20th June 2022 30 / 100
- 35. CP decomposition Goal: Decompose a tensor W to a sequence of low-rank components. In matrix form: W(1) . = U[1] J2 m=M U[m] T where {U[m]}M m=1 are the factor matrices. A schematic of the CP decomposition of a third-order tensor W is: Figure: CP decomposition of a third-order tensor. High-degree polynomial expansions 20th June 2022 30 / 100
- 36. Outline 1 Introduction 2 Higher-degree polynomial expansions Polynomial expansion with respect to an input vector 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 31 / 100
- 37. Polynomial approximation Approximate the τth element G(z)τ with a Nth-degree polynomial: (G(z))τ ≈ βτ + d X i=1 w [1] τ,i zi + d X i=1 d X j=1 w [2] τ,i,jzi zj + · · · + d X i=1 d X j=1 . . . d X k=1 | {z } N summations w [N] τ,i,j,...,kzi zj . . . zk (4) Both βτ ∈ R and the set of tensors W[n] τ ∈ R Qn m=1 ×md N n=1 are learnable parameters. High-degree polynomial expansions 20th June 2022 32 / 100
- 38. Polynomial approximation The last equation (4) can be written in the tensor format as: (G(z))τ ≈ βτ + w[1] τ T z + zT W[2] τ z + · · · + W[N] τ N Y n=1 ×nz (5) By stacking the polynomials for all elements τ ∈ [1, . . . , o], we obtain: G(z) ≈ N X n=1 W[n] n+1 Y j=2 ×jz + β (6) From Stone-Weierstrass theorem, a polynomial can approximate any smooth function. High-degree polynomial expansions 20th June 2022 33 / 100
- 39. Polynomial approximation - learnable parameters The learnable parameters of (6) are Θ(dN). High-degree polynomial expansions 20th June 2022 34 / 100
- 40. Polynomial approximation - learnable parameters The learnable parameters of (6) are Θ(dN). A solution to reduce them: demand each factor W[n] to be low-rank. High-degree polynomial expansions 20th June 2022 35 / 100
- 41. Outline 1 Introduction 2 Higher-degree polynomial expansions Tensor decomposition per degree 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 36 / 100
- 42. Tensor decomposition per degree First solution: Demand each factor W[n] to be low-rank. Apply CP decomposition to each factor W[n] . Then, the expansion for N = 3 is: y = β + CT 1,[1]z + CT 1,[2]z ∗ CT 2,[2]z + CT 1,[3]z ∗ CT 2,[3]z ∗ CT 3,[3]z (7) G Chrysos*, M Georgopoulos*, J Deng, J Kossaifi, Y Panagakis, A Anandkumar, ‘Augmenting Deep Classifiers with Polynomial Neural Networks.’ European Conference on Computer Vision (ECCV), 2022. High-degree polynomial expansions 20th June 2022 37 / 100
- 43. Khatri-Rao to Hadamard product Lemma (Chrysos’19) For a set of N matrices {A[ν] ∈ RIν ×K }N ν=1 and {B[ν] ∈ RIν ×L}N ν=1, the following equality holds: ( N K ν=1 A[ν])T · ( N K ν=1 B[ν]) = (AT [1] · B[1]) ∗ . . . ∗ (AT [N] · B[N]), (8) where the symbol ‘∗’ denotes the Hadamard product. G Chrysos, S Moschoglou, Y Panagakis, and S Zafeiriou. ‘Polygan: High-order polynomial generators.’ arXiv preprint arXiv:1908.06571. High-degree polynomial expansions 20th June 2022 38 / 100
- 44. Factorization of Univariate Polynomials Over Finite Fields Berlekamp’s algorithm (1970): only practical over small finite fields. Cantor–Zassenhaus Algorithm (1981): Probabilistic algorithms. Victor Shoup Algorithm (1990): Deterministic algorithm. E Berlekamp. ‘Factoring Polynomials Over Large Finite Fields.’ In Mathematics of Computation, 1970. D Cantor, H Zassenhaus. ‘A New Algorithm for Factoring Polynomials Over Finite Fields.’ In Mathematics of Computation, 1981. V Shoup. ‘On the deterministic complexity of factoring polynomials over finite fields.’ In Information Processing Letters, 1990. High-degree polynomial expansions 20th June 2022 39 / 100
- 45. Decoupling Multivariate Polynomials Factorizing multivariate polynomials as a linear combination of univariate polynomials has been studied using tensor decompositions. Using first-order information and CP decomposition. Obtain a decomposition of the form: fi (u1, . . . , um) = r X j=1 wij · gj m X k=1 vkjuk , ∀i = 1, . . . , n , Matrix form decoupled representation: f (u) = Wg(V⊤ u) , P. Dreesen, M. Ishteva, J. Schoukens. ‘Decoupling Multivariate Polynomials Using First-Order Information and Tensor Decompositions.’ Journal on Matrix Analysis and Applications, 2015. High-degree polynomial expansions 20th June 2022 40 / 100
- 46. Outline 1 Introduction 2 Higher-degree polynomial expansions Π−nets: Joint decompositions across degrees 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 41 / 100
- 47. Π-nets: Third-degree expansion schematic - Model CCP Figure: Third-degree expansion. G Chrysos, S Moschoglou, Y Panagakis, and S Zafeiriou. ‘Polygan: High-order polynomial generators.’ arXiv preprint arXiv:1908.06571. G Chrysos, S Moschoglou, G Bouritsas, Y Panagakis, J Deng, and S Zafeiriou. ‘Π-nets: Deep Polynomial Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2020. High-degree polynomial expansions 20th June 2022 42 / 100
- 48. Π-nets: Third-degree expansion schematic - Model CCP Figure: Third-degree expansion. G Chrysos, S Moschoglou, Y Panagakis, and S Zafeiriou. ‘Polygan: High-order polynomial generators.’ arXiv preprint arXiv:1908.06571. G Chrysos, S Moschoglou, G Bouritsas, Y Panagakis, J Deng, and S Zafeiriou. ‘Π-nets: Deep Polynomial Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2020. High-degree polynomial expansions 20th June 2022 42 / 100
- 49. Π-nets: Third-degree expansion schematic - Model CCP Figure: Third-degree expansion. G Chrysos, S Moschoglou, Y Panagakis, and S Zafeiriou. ‘Polygan: High-order polynomial generators.’ arXiv preprint arXiv:1908.06571. G Chrysos, S Moschoglou, G Bouritsas, Y Panagakis, J Deng, and S Zafeiriou. ‘Π-nets: Deep Polynomial Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2020. High-degree polynomial expansions 20th June 2022 42 / 100
- 50. Π-nets: Third-degree expansion schematic - Model CCP Figure: Third-degree expansion. G Chrysos, S Moschoglou, Y Panagakis, and S Zafeiriou. ‘Polygan: High-order polynomial generators.’ arXiv preprint arXiv:1908.06571. G Chrysos, S Moschoglou, G Bouritsas, Y Panagakis, J Deng, and S Zafeiriou. ‘Π-nets: Deep Polynomial Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2020. High-degree polynomial expansions 20th June 2022 42 / 100
- 51. Π−nets - Model CCP We use a coupled CP decomposition, i.e., factor sharing in different levels. To demonstrate the method, we assume a third degree expansion, i.e., N = 3 in (6). Then, the expansion is: G(z) = β + W[1] z + W[2] ×2 z ×3 z + W[3] ×2 z ×3 z ×4 z (9) High-degree polynomial expansions 20th June 2022 43 / 100
- 52. Π−nets - Third-degree expansion - Model CCP We use the following factorizations: Let W[1] = CUT [1], be the parameters for first level of approximation. Assume W[2] = W [2] 1:2 + W [2] 1:3. We use a coupled CP decomposition which results in the following matrix form: W [2] (1) = C(U[3] ⊙ U[1])T + C(U[2] ⊙ U[1])T . Let the third-degree parameters: W [3] (1) = C(U[3] ⊙ U[2] ⊙ U[1])T . High-degree polynomial expansions 20th June 2022 44 / 100
- 53. Π−nets - Nth degree expansion The derivation can be extended to an arbitrary degree with the following recursive formulation: xn = UT [n]z ∗ xn−1 + xn−1 , (CCP) for n = 2, . . . , N with x1 = UT [1]z and x = CxN + β. The parameters C ∈ Ro×k, U[n] ∈ Rd×k for n = 1, . . . , N are learnable. High-degree polynomial expansions 20th June 2022 45 / 100
- 54. Π−nets - Alternative models Model CCP above assumes a certain factorization, e.g., W[2] = W [2] 1:2 + W [2] 1:3. New models can be derived by changing the assumptions. For instance, what if we assume that the tensors admit nested decompositions? High-degree polynomial expansions 20th June 2022 46 / 100
- 55. Π-nets: Model NCP The model with nested decompositions, called NCP, for N = 3: b[1] B[1] ∗ S[2] + ∗ S[3] + ∗ C + A[1] A[2] A[3] z B[2] B[3] b[2] b[3] β G(z) Figure: Third-degree expansion. High-degree polynomial expansions 20th June 2022 47 / 100
- 56. Π-nets: Model NCP The derivation can be extended to an arbitrary degree with the following recursive formulation: xn = AT [n]z ∗ ST [n]xn−1 + BT [n]b[n] , (NCP) for n = 2, . . . , N with x1 = AT [1]z ∗ BT [1]b[1] and x = CxN + β. High-degree polynomial expansions 20th June 2022 48 / 100
- 57. Π-nets: Product of polynomials The previous formulations, e.g. (CCP), require Θ(N) layers for Nth degree expansion. Can we achieve a higher degree expansion with less parameters? Yes. For instance, by stacking lower-degree polynomials sequentially. z · · · G(z) Order 2 Order 2 Order 2N ∗ ∗ Figure: Stacking N polynomials of degree 2, results in a 2N polynomial expansion. High-degree polynomial expansions 20th June 2022 49 / 100
- 58. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 50 / 100
- 59. Performance of polynomial expansions (with batch normalization) on CIFAR10, CIFAR100 benchmarks. Table: Polynomial expansion versus baselines. CIFAR10 CIFAR100 2−degree products 0.907 ± 0.003 0.667 ± 0.003 ResNet18∗ 0.391 ± 0.001 0.168 ± 0.001 ResNet18 0.945 ± 0.000 0.756 ± 0.001 High-degree polynomial expansions 20th June 2022 51 / 100
- 60. SORT model The model obtains the following formulation: x = UT [1]z + UT [2]z + UT [1]z ∗ UT [2]z . (10) Y Wang, L Xie, C Liu, Y Zhang, W Zhang, A Yuille. ‘SORT: Second-Order Response Transform for Visual Recognition.’ International Conference on Computer Vision (ICCV), 2017. High-degree polynomial expansions 20th June 2022 52 / 100
- 61. Squeeze-and-Excitation network Squeeze-and-Excitation network (SENet): The output of the SENet block YSE with respect to input X ∈ Rhw×C (h is the height, w is the width) can be formulated as: YSE = (XW1) ∗ r(p(XW1)W2) = (XW1) ∗ − → 1 1 hw − → 1 T XW1 W2 T (11) where W1, W2 are learnable parameters. J Hu, L Shen, G Sun. ’Squeeze-and-excitation networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2018. High-degree polynomial expansions 20th June 2022 53 / 100
- 62. Non-local (NL) neural network Non-local (NL) neural network: The output of the non-local block YNL ∈ RN×C with respect to input X ∈ RN×C can be formulated as: YNL = (XW1W⊤ 2 X⊤ )(XW3), (12) where W1, W2, W3 ∈ RC×C are learnable parameters. Scales quadratically with the dimension N (i.e. O(N2) complexity). X Wang, R Girshick, A Gupta, K He. ’Non-local Neural Networks.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2018. High-degree polynomial expansions 20th June 2022 54 / 100
- 63. Poly-NL Poly-NL: The output YPoly-NL ∈ RN×C is expressed by Using 3 degree polynomial nets as non-local self-attention block: YPoly-NL = (Φ(XW1 ∗ XW2) ∗ X)W3, (13) where learnable parameters W1, W2, W3 ∈ RC×C . Scales linearly with the dimension N (i.e. O(N) complexity). F Babiloni, et al. ‘Poly-NL: Linear Complexity Non-local Layers with Polynomials.’ In International Conference on Computer Vision (ICCV), 2021. High-degree polynomial expansions 20th June 2022 55 / 100
- 64. Linear Complexity Self-Attention with Polynomials Poly-NL reformulates SA using only global descriptors and element-wise multiplications, achieving Linear Complexity O(N). High-degree polynomial expansions 20th June 2022 56 / 100
- 65. Poly-NL: Space and Time Complexity (a) (b) Figure: Poly-NL achieves up to 10× speed up in run-time and a 5× less complexity overhead wrt NL. High-degree polynomial expansions 20th June 2022 57 / 100
- 66. Non-local with lower-degree interactions PDC-NL: Y = (XW1W⊤ 2 X⊤)(XW3) + XW4XW5 + XW6 Includes first to third degrees term based on NL (only third degree). G Chrysos*, M Georgopoulos*, J Deng, J Kossaifi, Y Panagakis, A Anandkumar, ‘Augmenting Deep Classifiers with Polynomial Neural Networks.’ European Conference on Computer Vision (ECCV), 2022. High-degree polynomial expansions 20th June 2022 58 / 100
- 67. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 59 / 100
- 68. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks Unconditional generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 60 / 100
- 69. Expressivity - Generation without activation functions Results from a generator with convolutional layers without activations: High-degree polynomial expansions 20th June 2022 61 / 100
- 70. Expressivity of Π−nets We consider image generation without activation functions between the layers. Synthesized images: High-degree polynomial expansions 20th June 2022 62 / 100
- 71. Expressivity of Π−nets Linear interpolation in the latent space: High-degree polynomial expansions 20th June 2022 63 / 100
- 72. Image generation from a polynomial generator High-degree polynomial expansions 20th June 2022 64 / 100
- 73. Π−nets on non-euclidean representation learning Beyond image generation, polynomial nets perform well in non-euclidean representation learning. Code: https://github.com/grigorisg9gr/polynomial_nets G Chrysos, S Moschoglou, G Bouritsas, J Deng, Y Panagakis, and S Zafeiriou. ‘Deep Polynomial Neural Networks.’ IEEE Transactions on Pattern Analysis and Machine Intelligence (T-PAMI), 2021. High-degree polynomial expansions 20th June 2022 65 / 100
- 74. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks Synthesizing unseen combinations 5 Future directions High-degree polynomial expansions 20th June 2022 66 / 100
- 75. Conditional data generation: Visual examples Figure: Image-to-image translation examples. Phillip Isola, et al. ’A Image-to-image translation with conditional adversarial networks’, Conference on Computer Vision and Pattern Recognition (CVPR) 2017. Mehdi Mirza and Simon Osindero. ’Conditional generative adversarial nets’, CoRR 2014. High-degree polynomial expansions 20th June 2022 67 / 100
- 76. Attribute-conditional generative models High-degree polynomial expansions 20th June 2022 68 / 100
- 77. Attribute-conditional generative models and generalization High-degree polynomial expansions 20th June 2022 69 / 100
- 78. Conditional Variational Autoencoder (cVAE) High-degree polynomial expansions 20th June 2022 70 / 100
- 79. MLC-VAE - Our framework We instead model each attribute combination with a different mean. How to obtain the mean: M(y1, y2) = W[1] y1 + W[2] y2 + W[12] ×2 y1 ×3 y2, (14) for attributes y1, y2. M Georgopoulos, G Chrysos, M Pantic, and Y Panagakis. ‘Multilinear Latent Conditioning for Generating Unseen Attribute Combinations.’ In International Conference on Machine Learning (ICML), 2020. High-degree polynomial expansions 20th June 2022 71 / 100
- 80. MLC-VAE - Results High-degree polynomial expansions 20th June 2022 72 / 100
- 81. MLC-VAE - Multiplicative interactions Can we use additive interactions instead? Not really. For instance, synthesize images with attributes (’smile’ and ’closed mouth’). High-degree polynomial expansions 20th June 2022 73 / 100
- 82. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks Conditional image generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 74 / 100
- 83. Diverse samples in conditional generation Figure: In addition to the adversarial loss of GANs, regularization losses are typically used for enabling diverse synthesis. Q Mao, H Lee, H Tseng, S Ma, M Yang. ‘Mode Seeking Generative Adversarial Networks for Diverse Image Synthesis.’ In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2019. High-degree polynomial expansions 20th June 2022 75 / 100
- 84. Conditional image generation - Introduction 1 Conditioning the generator still relies on the neural network for the expressivity. 2 Can we use high-degree polynomial expansions instead? 3 Assume zI, zII ∈ Rd are the input vectors. The goal is to learn a function G : Rd×d → Ro that captures the higher-order correlations between the elements of the two inputs. High-degree polynomial expansions 20th June 2022 76 / 100
- 85. CoPE: Nth -degree expansion - Model CCP The recursive formulation of CoPE is given by: xn = xn−1 + UT [n,I]zI + UT [n,II]zII ∗ xn−1, (15) for n = 2, . . . , N with x1 = UT [1,I]zI + UT [1,II]zII and x = CxN + β. The schematic illustration is the following: Figure: Nth -degree expansion for conditional generation. G Chrysos, M Georgopoulos, and Y Panagakis. ‘Conditional Generation Using Polynomial Expansions.’ In Advances in neural information processing systems (NeurIPS), 2021. High-degree polynomial expansions 20th June 2022 77 / 100
- 86. CoPE: Nth -degree expansion - Model CCP The recursive formulation of CoPE is given by: xn = xn−1 + UT [n,I]zI + UT [n,II]zII ∗ xn−1, (15) for n = 2, . . . , N with x1 = UT [1,I]zI + UT [1,II]zII and x = CxN + β. The schematic illustration is the following: Figure: Nth -degree expansion for conditional generation. G Chrysos, M Georgopoulos, and Y Panagakis. ‘Conditional Generation Using Polynomial Expansions.’ In Advances in neural information processing systems (NeurIPS), 2021. High-degree polynomial expansions 20th June 2022 77 / 100
- 87. Synthesized images with CoPE (a) edges-to-handbags (b) edges-to-shoes Figure: The first row depicts the conditional input (i.e., the edges). The rows 2-6 depict outputs when we vary zI (i.e., noise). High-degree polynomial expansions 20th June 2022 78 / 100
- 88. Beyond two-variable expansion with CoPE The recursive formulation can be extended beyond two-variable expansions. For three-variables the formulation is the following: xn = xn−1 + UT [n,I]zI + UT [n,II]zII + UT [n,III]zIII ∗ xn−1, (16) for n = 2, . . . , N with x1 = UT [1,I]zI +UT [1,II]zII +UT [1,III]zIII and x = CxN +β. Code: https://github.com/grigorisg9gr/polynomial_nets_for_conditional_generation High-degree polynomial expansions 20th June 2022 79 / 100
- 89. Beyond two-variable expansion with CoPE Synthesized images on conditional generation with 2 attributes: (a) (b) Figure: (a) Each row/column depicts a different hair/eye color respectively, (b) synthesized images per unique combination by varying the noise zI. High-degree polynomial expansions 20th June 2022 80 / 100
- 90. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks Audio synthesis 5 Future directions High-degree polynomial expansions 20th June 2022 81 / 100
- 91. Audio representation Time domain VS Frequency domain Figure: Source: https://www.nti-audio.com/en/support/know-how/fast-fourier-transform-fft High-degree polynomial expansions 20th June 2022 82 / 100
- 92. How to model the complex-valued frequency representations? Real-valued neural networks (RVNNs) with 1 output channel for the magnitude of complex-valued representations: Discard the phase information. Require phase reconstruction in a generative task. RVNNs with 2 output channels for complex-valued representations: Higher degree of freedom at the synaptic weighting. Lower generalization ability. How about directly modelling the complex-valued representations? A Hirose, S. Yoshida. ’Generalization Characteristics of Complex-Valued Feedforward Neural Networks in Relation to Signal Coherence.’ IEEE Transactions on Neural Networks and Learning Systems, 2012. High-degree polynomial expansions 20th June 2022 83 / 100
- 93. Mergelyan’s Theorem Suppose K is a compact set in the plane whose complement is connected, f is a continuous complex-valued function defined on K which is holomorphic in the interior of K, and if ϵ 0, then there exists a polynomial P such that |f (x) − P(x)| ϵ for all x ∈ K. W Rudin. ’Real and Complex Analysis.’ McGraw-Hill International Series, 1987. High-degree polynomial expansions 20th June 2022 84 / 100
- 94. Schematic of the generator Audiorepresentation in frequencydomain Complex-valued randomnoise Audiorepresentation in frequencydomain Complex-valued randomnoise ... ... ... from degreeto degree APOLLOgenerator (Model BN) Yongtao Wu, G Chrysos, Volkan Cevher. ’Adversarial Audio Synthesis with Complex-valued Polynomial Networks.’ 2022. High-degree polynomial expansions 20th June 2022 85 / 100
- 95. Model in the complex field CFBN (Nested CP decomposition with bias): The recursive form for Nth degree expansion is: e yn = ET [n]e x + ρ[n] ∗ FT [n]e yn−1 + b[n] + e yn−1, (17) for n = 2, . . . , N with e y1 = (e ET [1] e x) ∗ e b[1] , e y = e He yN + e h, where we denote by e b[n] = e BT [n] e β[n] for n = 1, . . . , N. High-degree polynomial expansions 20th June 2022 86 / 100
- 96. Unsupervised audio generation on SC09 dataset Model IS (↑) FID (↓) NDB (↓) JSD (↓) # par (M) Real data 8.01 ± 0.24 0.50 0.00 ± 0.00 0.011 WaveGAN 4.67 ± 0.01 41.60 16.00 ± 1.09 0.094 36.5 . SpecGAN 6.03 ± 0.04 36.5 TiFGAN 5.97 26.70 6.00 ± 0.89 0.051 42.4 StyleGAN-U2 27.10 48.7 Unsupervised BigGAN 6.17 ± 0.20 24.72 Π-Nets 6.59 ± 0.03 13.01 4.40 ± 0.48 0.048 45.9 APOLLO, Small 6.48 ± 0.05 18.90 4.20 ± 1.47 0.038 4.6 APOLLO 7.25 ± 0.05 8.15 3.20 ± 1.16 0.029 64.1 High-degree polynomial expansions 20th June 2022 87 / 100
- 97. Human evaluation Human evaluation on unsupervised audio generation on SC09 dataset. From left to right in the histogram, the Mean Opinion Score (MOS) for all models and the real data are 1.61, 2.68, 2.73, 3.33, and 4.73, respectively. APOLLO -Nets Real TiFGAN WaveGAN Rating High-degree polynomial expansions 20th June 2022 88 / 100
- 98. Multimodal generation: Image-to-speech High-degree polynomial expansions 20th June 2022 89 / 100
- 99. Highway networks 2nd degree Increasing degree MLP (Identity activation) 1st degree 3rd degree Higher degree LSTM Gating MLC-VAE Bilinear form Squeeze and excitation nets StyleGAN -Nets APOLLO COPE PDC Non-local networks Self-attention Metric learning Polynomial nets Mahalanobis distance ResNet RNN Multiplicative RNN Higher order tensor RNN High-degree polynomial expansions 20th June 2022 90 / 100
- 100. Outline 1 Introduction 2 Higher-degree polynomial expansions 3 Object recognition with polynomial networks 4 Data generation with polynomial networks 5 Future directions High-degree polynomial expansions 20th June 2022 91 / 100
- 101. Complementary work on polynomial networks I 1 Polynomial networks can enlarge the hypothesis space [Jayakumar’20, Fan’21]. S Jayakumar, et al. ‘Multiplicative Interactions and Where to Find Them.’ In International Conference on Learning Representations (ICLR), 2020. FL Fan, et al. ‘Expressivity and Trainability of Quadratic Networks.’ ArXiv preprint arXiv:2110.06081. S Zhang, Y Gong, D Yu, ‘Encrypted Speech Recognition using Deep Polynomial Networks.’ In International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2019. Z Zhu, et al. ‘Controlling the Complexity and Lipschitz Constant improves Polynomial Nets’ In International Conference on Learning Representations (ICLR), 2022. High-degree polynomial expansions 20th June 2022 92 / 100
- 102. Complementary work on polynomial networks I 1 Polynomial networks can enlarge the hypothesis space [Jayakumar’20, Fan’21]. 2 Privacy-preserving applications require polynomial expansions [Zhang’19]. S Jayakumar, et al. ‘Multiplicative Interactions and Where to Find Them.’ In International Conference on Learning Representations (ICLR), 2020. FL Fan, et al. ‘Expressivity and Trainability of Quadratic Networks.’ ArXiv preprint arXiv:2110.06081. S Zhang, Y Gong, D Yu, ‘Encrypted Speech Recognition using Deep Polynomial Networks.’ In International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2019. Z Zhu, et al. ‘Controlling the Complexity and Lipschitz Constant improves Polynomial Nets’ In International Conference on Learning Representations (ICLR), 2022. High-degree polynomial expansions 20th June 2022 92 / 100
- 103. Complementary work on polynomial networks I 1 Polynomial networks can enlarge the hypothesis space [Jayakumar’20, Fan’21]. 2 Privacy-preserving applications require polynomial expansions [Zhang’19]. 3 Sample complexity (and similar theoretical bounds) might be simpler to compute [Zhu’22]. S Jayakumar, et al. ‘Multiplicative Interactions and Where to Find Them.’ In International Conference on Learning Representations (ICLR), 2020. FL Fan, et al. ‘Expressivity and Trainability of Quadratic Networks.’ ArXiv preprint arXiv:2110.06081. S Zhang, Y Gong, D Yu, ‘Encrypted Speech Recognition using Deep Polynomial Networks.’ In International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2019. Z Zhu, et al. ‘Controlling the Complexity and Lipschitz Constant improves Polynomial Nets’ In International Conference on Learning Representations (ICLR), 2022. High-degree polynomial expansions 20th June 2022 92 / 100
- 104. Complementary work on polynomial networks I 1 Polynomial networks can enlarge the hypothesis space [Jayakumar’20, Fan’21]. 2 Privacy-preserving applications require polynomial expansions [Zhang’19]. 3 Sample complexity (and similar theoretical bounds) might be simpler to compute [Zhu’22]. 4 Known (theoretical) results from neural networks might not be directly applicable (e.g., implicit bias). S Jayakumar, et al. ‘Multiplicative Interactions and Where to Find Them.’ In International Conference on Learning Representations (ICLR), 2020. FL Fan, et al. ‘Expressivity and Trainability of Quadratic Networks.’ ArXiv preprint arXiv:2110.06081. S Zhang, Y Gong, D Yu, ‘Encrypted Speech Recognition using Deep Polynomial Networks.’ In International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2019. Z Zhu, et al. ‘Controlling the Complexity and Lipschitz Constant improves Polynomial Nets’ In International Conference on Learning Representations (ICLR), 2022. High-degree polynomial expansions 20th June 2022 92 / 100
- 105. Theoretical characterization of polynomial networks 0 200 400 600 800 1000 Polynomial degree 10-3 10-2 10-1 100 101 Test loss Test loss Figure: Double descent curve on polynomial regression. Source: https: // windowsontheory. org/ 2019/ 12/ 05/ deep-double-descent/ High-degree polynomial expansions 20th June 2022 93 / 100
- 106. Optimization and training 1 Multiplications can make the loss surface less well behaved [Schwarz et al.]. How should we adapt the optimizers for polynomial architectures? J Schwarz, S Jayakumar, R Pascanu, P Latham, T W Teh. ’Powerpropagation: A sparsity inducing weight reparameterisation.’ In Advances in neural information processing systems (NeurIPS), 2021. High-degree polynomial expansions 20th June 2022 94 / 100
- 107. Optimization and training 1 Multiplications can make the loss surface less well behaved [Schwarz et al.]. How should we adapt the optimizers for polynomial architectures? 2 What is the interaction between model degree and implicit regularization in polynomial networks? J Schwarz, S Jayakumar, R Pascanu, P Latham, T W Teh. ’Powerpropagation: A sparsity inducing weight reparameterisation.’ In Advances in neural information processing systems (NeurIPS), 2021. High-degree polynomial expansions 20th June 2022 94 / 100
- 108. Optimization and training 1 Multiplications can make the loss surface less well behaved [Schwarz et al.]. How should we adapt the optimizers for polynomial architectures? 2 What is the interaction between model degree and implicit regularization in polynomial networks? 3 How should we initialize polynomial networks? J Schwarz, S Jayakumar, R Pascanu, P Latham, T W Teh. ’Powerpropagation: A sparsity inducing weight reparameterisation.’ In Advances in neural information processing systems (NeurIPS), 2021. High-degree polynomial expansions 20th June 2022 94 / 100
- 109. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? High-degree polynomial expansions 20th June 2022 95 / 100
- 110. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? 2 How can we evaluate the differences of those architectures? High-degree polynomial expansions 20th June 2022 95 / 100
- 111. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? 2 How can we evaluate the differences of those architectures? 3 How can we determine the degree required by the task at hand? High-degree polynomial expansions 20th June 2022 95 / 100
- 112. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? 2 How can we evaluate the differences of those architectures? 3 How can we determine the degree required by the task at hand? 1 Is higher degree always better? High-degree polynomial expansions 20th June 2022 95 / 100
- 113. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? 2 How can we evaluate the differences of those architectures? 3 How can we determine the degree required by the task at hand? 1 Is higher degree always better? 2 Where should we have this higher degree? High-degree polynomial expansions 20th June 2022 95 / 100
- 114. Architecture 1 Can we use other popular tensor factorizations, e.g. Tucker decomposition, to obtain useful architectures? 2 How can we evaluate the differences of those architectures? 3 How can we determine the degree required by the task at hand? 1 Is higher degree always better? 2 Where should we have this higher degree? 3 Is there a total degree that is sufficient for all standard tasks? High-degree polynomial expansions 20th June 2022 95 / 100
- 115. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? High-degree polynomial expansions 20th June 2022 96 / 100
- 116. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? 5 Can we represent all signals of interest with a sequence of polynomial expansions? High-degree polynomial expansions 20th June 2022 96 / 100
- 117. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? 5 Can we represent all signals of interest with a sequence of polynomial expansions? 6 How should we reason about activations often used in conjunction with a polynomial form? High-degree polynomial expansions 20th June 2022 96 / 100
- 118. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? 5 Can we represent all signals of interest with a sequence of polynomial expansions? 6 How should we reason about activations often used in conjunction with a polynomial form? 1 Are activations required? High-degree polynomial expansions 20th June 2022 96 / 100
- 119. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? 5 Can we represent all signals of interest with a sequence of polynomial expansions? 6 How should we reason about activations often used in conjunction with a polynomial form? 1 Are activations required? 2 Are they mostly there to make learning possible? High-degree polynomial expansions 20th June 2022 96 / 100
- 120. Architecture II 4 How can we express a joint tensor decomposition over all sequential polynomial networks? 5 Can we represent all signals of interest with a sequence of polynomial expansions? 6 How should we reason about activations often used in conjunction with a polynomial form? 1 Are activations required? 2 Are they mostly there to make learning possible? 3 How do they modify the polynomial expansion? High-degree polynomial expansions 20th June 2022 96 / 100
- 121. Robustness of polynomial networks 1 A polynomial expansion with unconstrained input can obtain extremely large values. High-degree polynomial expansions 20th June 2022 97 / 100
- 122. Robustness of polynomial networks 1 A polynomial expansion with unconstrained input can obtain extremely large values. 2 How can we constrain their output range values efficiently? High-degree polynomial expansions 20th June 2022 97 / 100
- 123. Robustness of polynomial networks 1 A polynomial expansion with unconstrained input can obtain extremely large values. 2 How can we constrain their output range values efficiently? 3 How can we make polynomial nets robust to (adversarial) noise? High-degree polynomial expansions 20th June 2022 97 / 100
- 124. Demo code https://github.com/polynomial-nets/tutorial-2022-intro-polynomial-nets High-degree polynomial expansions 20th June 2022 98 / 100
- 125. Thank you for your attention 1 We would like to thank Francesca Babiloni, Leello Dadi, Zhenyu Zhu and Yongtao Wu for their help in preparing the tutorial. 2 Further information and materials can be found on https://polynomial-nets.github.io/. 3 Contact us: grigorios.chrysos [at] epfl.ch. High-degree polynomial expansions 20th June 2022 99 / 100
- 126. Highway networks 2nd degree Increasing degree MLP (Identity activation) 1st degree 3rd degree Higher degree LSTM Gating MLC-VAE Bilinear form Squeeze and excitation nets StyleGAN -Nets APOLLO COPE PDC Non-local networks Self-attention Metric learning Polynomial nets Mahalanobis distance ResNet RNN Multiplicative RNN Higher order tensor RNN High-degree polynomial expansions 20th June 2022 100 / 100