Boltzmann machines are often used as building blocks in greedy learning of deep networks. However, training even a simplified model, known as restricted Boltzmann machine (RBM), can be extremely laborious: Traditional learning algorithms often converge only with the right choice of the learning rate scheduling and the scale of the initial weights. They are also sensitive to specific data representation: An equivalent RBM can be obtained by flipping some bits and changing the weights and biases accordingly, but traditional learning rules are not invariant to such transformations. Without careful tuning of these training settings, traditional algorithms can easily get stuck at plateaus or even diverge. In this work, we present an enhanced gradient which is derived such that it is invariant to bitflipping transformations. We also propose a way to automatically adjust the learning rate by maximizing a local likelihood estimate. Our experiments confirm that the proposed improvements yield more stable training of RBMs. 1.

Abstract — A new interest towards restricted Boltzmann machines (RBMs) has risen due to their usefulness in greedy learning of deep neural networks. While contrastive divergence learning has been considered an efficient way to learn an RBM, it has a drawback due to a biased approximation in the learning gradient. We propose to use an advanced Monte Carlo method called parallel tempering instead, and show experimentally that it works efficiently. I.

Restricted Boltzmann Machines (RBM) are well-studied generative models. For image data, however, standard RBMs are suboptimal, since they do not exploit the local nature of image statistics. We modify RBMs to focus on local structure by restricting visible-hidden interactions. We model long-range interactions using direct or indirect lateral interaction between hidden variables. While learning in our model is much faster, it retains generative and discriminative properties of RBMs of similar complexity. 1

Abstract. We propose a few remedies to improve training of Gaussian-Bernoulli restricted Boltzmann machines (GBRBM), which is known to be difficult. Firstly, we use a different parameterization of the energy function, which allows for more intuitive interpretation of the parameters and facilitates learning. Secondly, we propose parallel tempering learning for GBRBM. Lastly, we use an adaptive learning rate which is selected automatically in order to stabilize training. Our extensive experiments show that the proposed improvements indeed remove most of the difficulties encountered when training GBRBMs using conventional methods.