Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning

Takeru MiyatoShin-ichi MaedaMasanori KoyamaShin Ishii

article2017TPAMI3,105 citations

Introduces Virtual Adversarial Training, a computationally efficient regularization technique that enforces prediction smoothness against label-free perturbations, successfully extending adversarial training to unlabeled data to improve semi-supervised classification performance.

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This paper introduces virtual adversarial training (VAT), a regularization technique designed to improve the generalization of neural networks in both supervised and semi-supervised settings. In practice, models often overfit finite training samples because their output distributions remain sensitive to small input perturbations in specific directions. Standard approaches such as random noise injection or adversarial training mitigate this issue only partially: the former applies isotropic smoothing that leaves models vulnerable to targeted perturbations, while the latter requires labeled data and therefore cannot be used when most examples are unlabeled.

The work sets out to define and evaluate a label-free regularization term that forces the conditional label distribution to be locally smooth around every input point, labeled or not. The method identifies the single direction of greatest sensitivitythe virtual adversarial directionby maximizing distributional divergence from the model’s current prediction at that point, then penalizes sensitivity along that direction. An efficient approximation based on one power iteration of the Hessian allows the penalty to be computed with only two additional forward-backward passes per example, keeping the added cost modest. Experiments were performed on the standard MNIST, SVHN, and CIFAR-10 benchmarks using both fully connected networks and convolutional architectures, with repeated runs under varied random seeds to report means and standard deviations.

VAT consistently reduced test error relative to random-perturbation baselines and to contemporary regularization methods. On supervised MNIST it reached 0.64 percent error, outperforming dropout and both L2- and L∞-constrained adversarial training. In the semi-supervised regime with only 1,000 labeled MNIST examples it achieved 1.36 percent error; on SVHN and CIFAR-10 with 1,000 and 4,000 labels respectively, the combination of VAT and conditional-entropy minimization produced state-of-the-art results (4.28 percent and 13.15 percent) without data augmentation. Adding moderate translation and flip augmentation further lowered these figures to 3.86 percent and 10.55 percent. A single power iteration proved sufficient in all reported settings, and the method required tuning of only one scalar hyper-parameterthe perturbation radiuswhile the regularization coefficient could be held at unity.

These gains arise because VAT directly regularizes the output distribution rather than the parameters, rendering the procedure invariant to reparameterization and allowing it to operate on unlabeled data. The resulting models also exhibit markedly lower error rates on virtual adversarial examples that remain visually indistinguishable from clean inputs. Limitations include restriction to image-classification benchmarks, dependence on appropriate choice of the perturbation radius, and the absence of direct comparisons against the strongest contemporary generative-model approaches on every task. Further work is warranted to combine VAT with generative semi-supervised methods, to test larger-scale architectures and non-image domains, and to develop adaptive schemes for selecting the perturbation radius without a held-out validation set.

  • Paper: Explaining and Harnessing Adversarial Examples, Ian J. Goodfellow et al. (2015). Reading this foundational work on adversarial examples provides the baseline threat model and linear explanation of vulnerability that virtual adversarial training builds upon.
Cover for Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning

Abstract

We propose a new regularization method based on virtual adversarial loss: a new measure of local smoothness of the conditional label distribution given input. Virtual adversarial loss is defined as the robustness of the conditional label distribution around each input data point against local perturbation. Unlike adversarial training, our method defines the adversarial direction without label information and is hence applicable to semi-supervised learning. Because the directions in which we smooth the model are only "virtually" adversarial, we call our method virtual adversarial training (VAT). The computational cost of VAT is relatively low. For neural networks, the approximated gradient of virtual adversarial loss can be computed with no more than two pairs of forward- and back-propagations. In our experiments, we applied VAT to supervised and semi-supervised learning tasks on multiple benchmark datasets. With a simple enhancement of the algorithm based on the entropy minimization principle, our VAT achieves state-of-the-art performance for semi-supervised learning tasks on SVHN and CIFAR-10.

Table of Contents

  • 1 INTRODUCTION
  • 2 RELATED WORKS
  • 3 METHODS
  • 3.1 Adversarial Training
  • 3.2 Virtual Adversarial Training
  • 3.3 Fast Approximation Method for rvadvr_{\text{vadv}} and the Derivative of the Objective Function
  • 3.4 Virtual Adversarial Training vs. Random Perturbation Training
  • 4 EXPERIMENTS
  • 4.1 Testing the Efficacy of VAT on Benchmark Tasks
  • 4.1.1 Supervised Learning on MNIST and CIFAR-10
  • 4.1.2 Semi-Supervised Learning on MNIST, SVHN, and CIFAR-10
  • 4.2 Effects of Perturbation Size ϵ\epsilon and Regularization Coefficient α\alpha
  • 4.3 Effect of the Number of the Power Iterations K
  • 4.4 Visualization of Virtual Adversarial Examples
  • 4.4.1 Virtual Adversarial Examples Produced by the Model Trained with Different Choices of \( \epsilon \)
  • 4.4.2 Robustness against Virtual Adversarial Examples after Training
  • 4.5 Experimental Assessment of the Difference between VAT and RPT
  • 5 CONCLUSIONS
  • APPENDIX A
  • SUPERVISED CLASSIFICATION FOR THE MNIST DATASET
  • APPENDIX B
  • SUPERVISED CLASSIFICATION FOR CIFAR-10 DATASET
  • APPENDIX C
  • SEMI-SUPERVISED CLASSIFICATION FOR THE MNIST DATASET
  • APPENDIX D
  • SEMI-SUPERVISED CLASSIFICATION FOR THE SVHN AND CIFAR-10 DATASETS

Knowls

  1. Knowl 1 — Virtual Adversarial Training (VAT) Objective and Local Distributional Smoothness

    model/method

    Virtual Adversarial Training (VAT) regularizes a conditional probability model p(yx,θ)p(y|x, \theta) by promoting local distributional smoothness (LDS) around each training input without requiring ground-truth labels. Let xRIx \in \mathbb{R}^I denote an input vector and yQy \in \mathcal{Q} denote the target label. Given a labeled dataset Dl={(xl(n),yl(n))}n=1Nl\mathcal{D}_l = \{(x_l^{(n)}, y_l^{(n)})\}_{n=1}^{N_l} and an unlabeled dataset Dul={xul(m)}m=1Nul\mathcal{D}_{ul} = \{x_{ul}^{(m)}\}_{m=1}^{N_{ul}}, let θ^\hat{\theta} denote the model parameter vector at the current training iteration.

    For any input xDlDulx_* \in \mathcal{D}_l \cup \mathcal{D}_{ul}, the virtual adversarial perturbation rvadvr_{\mathrm{vadv}} and local distributional smoothness loss LDS(x,θ)\mathrm{LDS}(x_*, \theta) are defined as:

    rvadv:=argmaxr;r2ϵD[p(yx,θ^),p(yx+r,θ^)]r_{\mathrm{vadv}} := \arg\max_{r; \|r\|_2 \le \epsilon} D[p(y|x_*, \hat{\theta}), p(y|x_* + r, \hat{\theta})]

    LDS(x,θ):=D[p(yx,θ^),p(yx+rvadv,θ)]\mathrm{LDS}(x_*, \theta) := D[p(y|x_*, \hat{\theta}), p(y|x_* + r_{\mathrm{vadv}}, \theta)]

    where ϵ>0\epsilon > 0 is the perturbation magnitude bound and D[p,p]D[p, p'] is a statistical divergence between categorical distributions pp and pp', chosen as the Kullback-Leibler (KL) divergence:

    D[p(yx),p(yx+r)]:=yQp(yx)logp(yx)p(yx+r)D[p(y|x), p(y|x+r)] := \sum_{y \in \mathcal{Q}} p(y|x) \log \frac{p(y|x)}{p(y|x+r)}

    The VAT regularizer is the empirical average of LDS over both labeled and unlabeled inputs:

    Rvadv(Dl,Dul,θ):=1Nl+NulxDlDulLDS(x,θ)\mathcal{R}_{\mathrm{vadv}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta) := \frac{1}{N_l + N_{ul}} \sum_{x_* \in \mathcal{D}_l \cup \mathcal{D}_{ul}} \mathrm{LDS}(x_*, \theta)

    The total training objective minimized over θ\theta is:

    (Dl,θ)+αRvadv(Dl,Dul,θ)\ell(\mathcal{D}_l, \theta) + \alpha \mathcal{R}_{\mathrm{vadv}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta)

    where (Dl,θ)\ell(\mathcal{D}_l, \theta) is the negative log-likelihood on labeled data and α>0\alpha > 0 is a regularization coefficient.

  2. Knowl 2 — Fast Approximation of Virtual Adversarial Perturbation via Power Iteration and Finite Differences

    model/method

    Because the gradient of the divergence D(r,x,θ^):=D[p(yx,θ^),p(yx+r,θ^)]D(r, x_*, \hat{\theta}) := D[p(y|x_*, \hat{\theta}), p(y|x_* + r, \hat{\theta})] with respect to perturbation vector rr satisfies rD(r,x,θ^)r=0=0\nabla_r D(r, x_*, \hat{\theta})|_{r=0} = 0, first-order linear approximation cannot determine rvadvr_{\mathrm{vadv}}. Assuming p(yx,θ)p(y|x, \theta) is twice differentiable with respect to xx and θ\theta almost everywhere, the second-order Taylor expansion around r=0r=0 yields:

    D(r,x,θ^)12rTH(x,θ^)rD(r, x_*, \hat{\theta}) \approx \frac{1}{2} r^T H(x_*, \hat{\theta}) r

    where H(x,θ^):=rD(r,x,θ^)r=0H(x_*, \hat{\theta}) := \nabla\nabla_r D(r, x_*, \hat{\theta})|_{r=0} is the Hessian matrix of DD with respect to rr evaluated at r=0r=0. Under this quadratic approximation, the virtual adversarial direction is the dominant eigenvector u(x,θ^)u(x_*, \hat{\theta}) of H(x,θ^)H(x_*, \hat{\theta}) with norm ϵ\epsilon:

    rvadvϵu(x,θ^)u(x,θ^)2r_{\mathrm{vadv}} \approx \epsilon \frac{u(x_*, \hat{\theta})}{\|u(x_*, \hat{\theta})\|_2}

    To avoid explicit O(I3)O(I^3) Hessian computation, the matrix-vector product HdH d for a random unit vector dRId \in \mathbb{R}^I is approximated with finite differences using a small scalar ξ0\xi \ne 0:

    HdrD(r,x,θ^)r=ξdrD(r,x,θ^)r=0ξ=rD(r,x,θ^)r=ξdξH d \approx \frac{\nabla_r D(r, x_*, \hat{\theta})|_{r=\xi d} - \nabla_r D(r, x_*, \hat{\theta})|_{r=0}}{\xi} = \frac{\nabla_r D(r, x_*, \hat{\theta})|_{r=\xi d}}{\xi}

    Executing K=1K=1 step of power iteration yields the efficient closed-form approximation:

    rvadvϵgg2,g=rD[p(yx,θ^),p(yx+r,θ^)]r=ξdr_{\mathrm{vadv}} \approx \epsilon \frac{g}{\|g\|_2}, \quad g = \nabla_r D[p(y|x_*, \hat{\theta}), p(y|x_* + r, \hat{\theta})]\Big|_{r=\xi d}

    where dN(0,I)d \sim \mathcal{N}(0, I) is normalized to unit length, and ξ\xi is set to 10610^{-6} in implementations.

  3. Knowl 3 — Mini-Batch SGD for Virtual Adversarial Training Gradient

    algorithm

    The gradient of the virtual adversarial regularizer θRvadv(θ)θ=θ^\nabla_\theta \mathcal{R}_{\mathrm{vadv}}(\theta)|_{\theta=\hat{\theta}} is approximated efficiently on a mini-batch of labeled and unlabeled data using a single power iteration (K=1K=1) and finite differences. The dependency of rvadvr_{\mathrm{vadv}} on θ\theta is treated as constant (stopping gradient at θ^\hat{\theta}) during parameter differentiation.

    Input: Dataset D=DlDul\mathcal{D} = \mathcal{D}_l \cup \mathcal{D}_{ul}, current parameter vector θ^\hat{\theta}, mini-batch size MM, finite difference scalar ξ>0\xi > 0, perturbation radius ϵ>0\epsilon > 0
    Output: Stochastic gradient vector GθθRvadv(θ)θ=θ^G_\theta \approx \nabla_\theta \mathcal{R}_{\mathrm{vadv}}(\theta)|_{\theta=\hat{\theta}}
    Sample a mini-batch of MM inputs {x(1),,x(M)}\{x^{(1)}, \dots, x^{(M)}\} from D\mathcal{D} uniformly at random
    for i=1i = 1 to MM do
        Sample v(i)N(0,I)v^{(i)} \sim \mathcal{N}(0, I)
        d(i)v(i)/v(i)2d^{(i)} \leftarrow v^{(i)} / \|v^{(i)}\|_2
        g(i)rD[p(yx(i),θ^),p(yx(i)+r,θ^)]r=ξd(i)g^{(i)} \leftarrow \nabla_r D[p(y|x^{(i)}, \hat{\theta}), p(y|x^{(i)} + r, \hat{\theta})]\Big|_{r = \xi d^{(i)}}
        rvadv(i)ϵ(g(i)/g(i)2)r_{\mathrm{vadv}}^{(i)} \leftarrow \epsilon \cdot (g^{(i)} / \|g^{(i)}\|_2)
    end for
    Gθθ(1Mi=1MD[p(yx(i),θ^),p(yx(i)+rvadv(i),θ)])θ=θ^G_\theta \leftarrow \nabla_\theta \left( \frac{1}{M} \sum_{i=1}^M D[p(y|x^{(i)}, \hat{\theta}), p(y|x^{(i)} + r_{\mathrm{vadv}}^{(i)}, \theta)] \right) \Bigg|_{\theta = \hat{\theta}}
    return GθG_\theta

    For neural networks, computing GθG_\theta requires K=1K=1 backward pass for the virtual adversarial directions rvadv(i)r_{\mathrm{vadv}}^{(i)} plus one forward/backward pass for θ\nabla_\theta, incurring at most three times the computational cost of standard unregularized backpropagation when combined with the supervised loss.

  4. Knowl 4 — Virtual Adversarial Training with Conditional Entropy Minimization (VAT+EntMin)

    model/method

    For semi-supervised classification, Virtual Adversarial Training can be combined with conditional entropy minimization on the model predictions over labeled and unlabeled data. The conditional entropy cost is defined as:

    Rcent(Dl,Dul,θ):=H(YX)=1Nl+NulxDlDulyQp(yx,θ)logp(yx,θ)\mathcal{R}_{\mathrm{cent}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta) := H(Y|X) = -\frac{1}{N_l + N_{ul}} \sum_{x \in \mathcal{D}_l \cup \mathcal{D}_{ul}} \sum_{y \in \mathcal{Q}} p(y|x, \theta) \log p(y|x, \theta)

    Minimizing Rcent\mathcal{R}_{\mathrm{cent}} encourages the classifier to make low-entropy, confident predictions (pushing class decision boundaries into low-density regions of the input distribution), while Rvadv\mathcal{R}_{\mathrm{vadv}} enforces local isotropy and smoothness. The combined objective function is:

    (Dl,θ)+αRvadv(Dl,Dul,θ)+Rcent(Dl,Dul,θ)\ell(\mathcal{D}_l, \theta) + \alpha \mathcal{R}_{\mathrm{vadv}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta) + \mathcal{R}_{\mathrm{cent}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta)

  5. Knowl 5 — Hyperparameter Equivalence of Perturbation Norm and Regularization Weight for Small Perturbations

    theoretical result

    For small perturbation magnitudes ϵ\epsilon, the second-order Taylor expansion of the local distributional smoothness around r=0r=0 yields:

    maxr;r2ϵD(r,x,θ)maxr;r2ϵ12rTH(x,θ)r=12ϵ2λ1(x,θ)\max_{r; \|r\|_2 \le \epsilon} D(r, x_*, \theta) \approx \max_{r; \|r\|_2 \le \epsilon} \frac{1}{2} r^T H(x_*, \theta) r = \frac{1}{2} \epsilon^2 \lambda_1(x_*, \theta)

    where λ1(x,θ)\lambda_1(x_*, \theta) is the largest eigenvalue of the Hessian matrix H(x,θ)=rD(r,x,θ)r=0H(x_*, \theta) = \nabla\nabla_r D(r, x_*, \theta)|_{r=0}. Consequently, the full VAT regularized objective satisfies:

    (Dl,θ)+αRvadv(Dl,Dul,θ)(Dl,θ)+12αϵ2(1Nl+NulxDlDulλ1(x,θ))\ell(\mathcal{D}_l, \theta) + \alpha \mathcal{R}_{\mathrm{vadv}}(\mathcal{D}_l, \mathcal{D}_{ul}, \theta) \approx \ell(\mathcal{D}_l, \theta) + \frac{1}{2} \alpha \epsilon^2 \left( \frac{1}{N_l + N_{ul}} \sum_{x_* \in \mathcal{D}_l \cup \mathcal{D}_{ul}} \lambda_1(x_*, \theta) \right)

    Thus, the effective regularization strength is governed by the product αϵ2\alpha \epsilon^2. In this regime, tuning the single scalar parameter ϵ\epsilon while keeping α=1\alpha = 1 fixed is sufficient to attain optimal regularization performance.

  6. Knowl 6 — Parameterization Invariance of Virtual Adversarial Regularization

    theoretical result

    A regularizer L(θ)L(\theta) is defined to be parameterization invariant if the optimal predictive distribution p(X;θ)p(X; \theta^*) is invariant under any smooth bijective parameter reparameterization ω=T(θ)\omega = T(\theta), θ=T1(ω)\theta = T^{-1}(\omega), satisfying p(X;θ)=p(X;ω)p(X; \theta^*) = p(X; \omega^*) where ω=argminωL(T1(ω);D)\omega^* = \arg\min_\omega L(T^{-1}(\omega); \mathcal{D}).

    Standard LpL_p parameter regularizers (such as weight decay) are not parameterization invariant in deep nonlinear networks: modifying early layer weights changes the output sensitivity differently depending on subsequent layer weight magnitudes. In contrast, VAT is parameterization invariant because Rvadv\mathcal{R}_{\mathrm{vadv}} directly regularizes the geometric sensitivity of the output conditional distribution p(yx)p(y|x) with respect to variations in the input space xx, which is functionally independent of the specific parameter coordinate representation θ\theta chosen for the neural network.

  7. Knowl 7 — Theoretical and Variance Comparison Between VAT and Random Perturbation Training

    theoretical result

    Random Perturbation Training (RPT) is the isotropic counterpart to VAT where perturbations r0r_0 are drawn uniformly at random from the ϵ\epsilon-sphere without power iteration (K=0K=0 in R(K)\mathcal{R}^{(K)}):

    R(0)(θ,Dl,Dul):=1Nl+NulxDlDulEr0U({r:r2=ϵ})[D[p(yx,θ^),p(yx+r0,θ)]]\mathcal{R}^{(0)}(\theta, \mathcal{D}_l, \mathcal{D}_{ul}) := \frac{1}{N_l + N_{ul}} \sum_{x \in \mathcal{D}_l \cup \mathcal{D}_{ul}} \mathbb{E}_{r_0 \sim \mathcal{U}(\{r: \|r\|_2 = \epsilon\})} \left[ D[p(y|x, \hat{\theta}), p(y|x + r_0, \theta)] \right]

    VAT differs from RPT in two ways:

    1. Spectral objective: VAT penalizes the spectral norm (dominant eigenvalue λ1\lambda_1) of the local Hessian H(x,θ)H(x, \theta), concentrating smoothing along the most sensitive anisotropic direction. In contrast, RPT penalizes the trace (sum of all eigenvalues iλi\sum_i \lambda_i) of H(x,θ)H(x, \theta).
    2. Gradient variance: The normalized standard deviation (SD) norm of the stochastic gradient:

    trace(VarDM,rK[θR^(K)(θ;DM,rK)])EDM,rK[θR^(K)(θ;DM,rK)]2\frac{\sqrt{\operatorname{trace}\left(\operatorname{Var}_{\mathcal{D}_M, r_K}\left[ \nabla_\theta \hat{\mathcal{R}}^{(K)}(\theta; \mathcal{D}_M, r_K) \right]\right)}}{\left\| \mathbb{E}_{\mathcal{D}_M, r_K}\left[ \nabla_\theta \hat{\mathcal{R}}^{(K)}(\theta; \mathcal{D}_M, r_K) \right] \right\|_2}

    is substantially lower for VAT (K=1K=1) than for RPT (K=0K=0) across training iterations, stabilizing optimization.

  8. Knowl 8 — Semi-Supervised Classification Benchmarks on SVHN and CIFAR-10 without Data Augmentation

    data/table

    Test error rates (%) of semi-supervised learning methods evaluated on SVHN (Nl=1000N_l = 1000 labeled images) and CIFAR-10 (Nl=4000N_l = 4000 labeled images) without image data augmentation. VAT and VAT+EntMin were tested using Conv-Small (structure from Salimans et al., 2016) and Conv-Large (structure from Laine and Aila, 2017) CNN architectures.

    Method Test error rate (%)
    SVHN (Nl=1000N_l = 1000) CIFAR-10 (Nl=4000N_l = 4000)
    SWWAE 23.56 -
    *Skip DGM 16.61 (±\pm0.24) -
    *Auxiliary DGM 22.86 -
    Ladder networks, Γ\Gamma model - 20.40 (±\pm0.47)
    CatGAN - 19.58 (±\pm0.58)
    GAN with Feature Matching 8.11 (±\pm1.3) 18.63 (±\pm2.32)
    Π\Pi model 5.43 (±\pm0.25) 16.55 (±\pm0.29)
    (on Conv-Small)
    RPT 8.41 (±\pm0.24) 18.56 (±\pm0.29)
    VAT 6.83 (±\pm0.24) 14.87 (±\pm0.13)
    (on Conv-Large)
    VAT 5.77 (±\pm0.32) 14.18 (±\pm0.38)
    VAT+EntMin 4.28 (±\pm0.10) 13.15 (±\pm0.21)

    Asterisk (*) denotes permutation-invariant models. Results demonstrate that VAT alone achieves 14.87% on CIFAR-10 with Conv-Small (outperforming GANs and Π\Pi models), and VAT+EntMin on Conv-Large attains the lowest error rates on both datasets.

  9. Knowl 9 — Semi-Supervised Classification Benchmarks on SVHN and CIFAR-10 with Moderate Data Augmentation

    data/table

    Test error rates (%) on SVHN (Nl=1000N_l = 1000) and CIFAR-10 (Nl=4000N_l = 4000) with moderate image data augmentation (random 2×22 \times 2 translations for both datasets, plus horizontal flips for CIFAR-10). VAT models were trained on the Conv-Large architecture.

    Method Test error rate (%)
    SVHN (Nl=1000N_l = 1000) CIFAR-10 (Nl=4000N_l = 4000)
    Π\Pi model 4.82 (±\pm0.17) 12.36 (±\pm0.31)
    Temporal ensembling 4.42 (±\pm0.16) 12.16 (±\pm0.24)
    Sajjadi et al. (extensive augmentation) - 11.29 (±\pm0.24)
    (On Conv-Large)
    VAT 5.42 (±\pm0.22) 11.36 (±\pm0.34)
    VAT+EntMin 3.86 (±\pm0.11) 10.55 (±\pm0.05)

    VAT+EntMin combined with moderate data augmentation achieves state-of-the-art error rates of 3.86% on SVHN and 10.55% on CIFAR-10, demonstrating that virtual adversarial regularization operates orthogonally to label-invariant spatial data augmentations.

  10. Knowl 10 — Supervised Learning Benchmark Performance on MNIST and CIFAR-10

    data/table

    Test error rates (%) for fully supervised classification on MNIST (60,000 labeled examples, 4-layer fully connected NN with layer sizes 1200-600-300-150 in the permutation-invariant setting) and CIFAR-10 (50,000 labeled examples, Conv-Large architecture with dropout and ZCA whitening preprocessing).

    MNIST (Permutation Invariant) CIFAR-10 (Conv-Large CNN)
    Method Error (%) Method Error (%)
    SVM (Gaussian kernel) 1.40 Network in Network 8.81
    Dropout 1.05 All-CNN 7.25
    Adversarial (LL_\infty) [Goodfellow 2015] 0.78 Deeply Supervised Net 7.97
    Ladder networks 0.57 (±\pm0.02) Highway Network 7.72
    Baseline (MLE) 1.11 (±\pm0.06) ResNet (1001 layers) 4.62 (±\pm0.20)
    RPT 0.84 (±\pm0.03) DenseNet (190 layers) 3.46
    Adversarial (LL_\infty) 0.79 (±\pm0.03) Baseline (dropout only) 6.67 (±\pm0.07)
    Adversarial (L2L_2) 0.71 (±\pm0.03) RPT 6.30 (±\pm0.04)
    VAT 0.64 (±\pm0.05) VAT 5.81 (±\pm0.02)

    On MNIST, supervised VAT achieves a 0.64% error rate, surpassing standard adversarial training with L2L_2 (0.71%) and LL_\infty (0.79%) norms as well as dropout (1.05%). On CIFAR-10 with standard Conv-Large CNN, VAT reduces test error from 6.67% (baseline) and 6.30% (RPT) down to 5.81%.

  11. Knowl 11 — Empirical Sufficiency of a Single Power Iteration ($K=1$)

    empirical result

    Evaluating semi-supervised VAT on CIFAR-10 (Nl=4000N_l = 4000, Conv-Large architecture) with varying numbers of power iterations KK yielded test error rates of:

    • K=1K = 1: 14.18%±0.38%14.18\% \pm 0.38\%
    • K=2K = 2: 14.19%±0.16%14.19\% \pm 0.16\%
    • K=4K = 4: 14.25%±0.18%14.25\% \pm 0.18\%

    Increasing KK beyond 1 provides negligible performance gain because the ratio between the first and second eigenvalues λ1/λ2\lambda_1 / \lambda_2 of the Hessian H(x,θ^)H(x, \hat{\theta}) is sufficiently large across empirical distributions, causing the dominant eigenvector estimate to saturate at K=1K=1.

Coverage note — None was omitted; all key definitions, mathematical formulations, approximation algorithms, theoretical properties, and empirical results were covered.

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Citation

MLA
Miyato, T., et al. “Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning”. IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 41, no. 8, 2019, pp. 1979–93, https://doi.org/10.1109/TPAMI.2018.2858821.
APA
Miyato, T., Maeda, S.-I., Koyama, M., & Ishii, S. (2019). Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning. IEEE Transactions on Pattern Analysis and Machine Intelligence, 41(8), 1979–1993. https://doi.org/10.1109/TPAMI.2018.2858821
Chicago
Miyato, T., S.-I. Maeda, M. Koyama, and S. Ishii. 2019. “Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning”. IEEE Transactions on Pattern Analysis and Machine Intelligence 41 (8): 1979–93. https://doi.org/10.1109/TPAMI.2018.2858821.
Harvard
Miyato, T. et al. (2019) “Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning”, IEEE Transactions on Pattern Analysis and Machine Intelligence, 41(8), pp. 1979–1993. Available at: https://doi.org/10.1109/TPAMI.2018.2858821.
Vancouver
1. Miyato T, Maeda S-I, Koyama M, Ishii S (2019) Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning. IEEE Transactions on Pattern Analysis and Machine Intelligence 41:1979–1993

BibTeX

@article{Miyato_2019, title={Virtual Adversarial Training: A Regularization Method for Supervised and Semi-Supervised Learning}, volume={41}, ISSN={1939-3539}, url={http://dx.doi.org/10.1109/TPAMI.2018.2858821}, DOI={10.1109/tpami.2018.2858821}, number={8}, journal={IEEE Transactions on Pattern Analysis and Machine Intelligence}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Miyato, Takeru and Maeda, Shin-Ichi and Koyama, Masanori and Ishii, Shin}, year={2019}, month=Aug, pages={1979–1993} }
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