34 research outputs found
Improving Compositional Generalization Using Iterated Learning and Simplicial Embeddings
Compositional generalization, the ability of an agent to generalize to unseen
combinations of latent factors, is easy for humans but hard for deep neural
networks. A line of research in cognitive science has hypothesized a process,
``iterated learning,'' to help explain how human language developed this
ability; the theory rests on simultaneous pressures towards compressibility
(when an ignorant agent learns from an informed one) and expressivity (when it
uses the representation for downstream tasks). Inspired by this process, we
propose to improve the compositional generalization of deep networks by using
iterated learning on models with simplicial embeddings, which can approximately
discretize representations. This approach is further motivated by an analysis
of compositionality based on Kolmogorov complexity. We show that this
combination of changes improves compositional generalization over other
approaches, demonstrating these improvements both on vision tasks with
well-understood latent factors and on real molecular graph prediction tasks
where the latent structure is unknown
Simplicial Embeddings in Self-Supervised Learning and Downstream Classification
We introduce Simplicial Embeddings (SEMs) as a way to constrain the encoded
representations of a self-supervised model to simplices of dimensions
each using a Softmax operation. This procedure imposes a structure on the
representations that reduce their expressivity for training downstream
classifiers, which helps them generalize better. Specifically, we show that the
temperature of the Softmax operation controls for the SEM
representation's expressivity, allowing us to derive a tighter downstream
classifier generalization bound than that for classifiers using unnormalized
representations. We empirically demonstrate that SEMs considerably improve
generalization on natural image datasets such as CIFAR-100 and ImageNet.
Finally, we also present evidence of the emergence of semantically relevant
features in SEMs, a pattern that is absent from baseline self-supervised
models.Comment: 22 pages, 5 figures, 5 tables, Preprin
Bigger, Better, Faster: Human-level Atari with human-level efficiency
We introduce a value-based RL agent, which we call BBF, that achieves
super-human performance in the Atari 100K benchmark. BBF relies on scaling the
neural networks used for value estimation, as well as a number of other design
choices that enable this scaling in a sample-efficient manner. We conduct
extensive analyses of these design choices and provide insights for future
work. We end with a discussion about updating the goalposts for
sample-efficient RL research on the ALE. We make our code and data publicly
available at
https://github.com/google-research/google-research/tree/master/bigger_better_faster.Comment: ICML 2023 Camera Read
Learning and Controlling Silicon Dopant Transitions in Graphene using Scanning Transmission Electron Microscopy
We introduce a machine learning approach to determine the transition dynamics
of silicon atoms on a single layer of carbon atoms, when stimulated by the
electron beam of a scanning transmission electron microscope (STEM). Our method
is data-centric, leveraging data collected on a STEM. The data samples are
processed and filtered to produce symbolic representations, which we use to
train a neural network to predict transition probabilities. These learned
transition dynamics are then leveraged to guide a single silicon atom
throughout the lattice to pre-determined target destinations. We present
empirical analyses that demonstrate the efficacy and generality of our
approach
Bridge to the stars: A mission concept to an interstellar object
Exoplanet discoveries since the mid-1990’s have revealed an astounding diversity of planetary systems. Studying these systems is essential to understanding planetary formation processes, as well as the development of life in the universe. Unfortunately, humanity can only observe limited aspects of exoplanetary systems by telescope, and the significant distances between stars presents a barrier to in situ exploration. In this study, we propose an alternative path to gain insight into exoplanetary systems: Bridge, a mission concept design to fly by an interstellar object as it passes through our solar system. Designed as a New Frontiers-class mission during the National Aeronautics and Space Administration (NASA) Planetary Science Summer School, Bridge would provide a unique opportunity to gain insight into potential physical, chemical, and biological differences between solar systems as well as the possible exchange of planetary materials between them. Bridge employs ultraviolet/visible, near-infrared, and mid-infrared point spectrometers, a visible camera, and a guided impactor. We also provide a quantitative Monte Carlo analysis that estimates wait times for a suitable target, and examines key trades between ground storage and a parking orbit, power sources, inner versus outer solar system encounters, and launch criteria. Due to the fleeting nature of interstellar objects, reaching an interstellar object may require an extended ground storage phase for the spacecraft until a suitable ISO is discovered, followed by a rapid response launch strategy. To enable rapid response missions designed to intercept such unique targets, language would need to be added to future NASA announcements of opportunity such that ground storage and rapid response would be allowable components of a proposed mission
Courville_etal_2022_planetesimal_thermal_models
Planetesimal thermal evolution models used in Courville et al. 2022, Acquisition and Preservation of Remanent Magnetization in Carbonaceous Asteroids
Kenyan nodular lymphocyte predominant Hodgkin lymphoma shares features with western cases and is not associated with EBV
Background: Pulmonary Langerhans cell histiocytosis (PLCH) is a distinctive form of tobacco associated interstitial lung disease. Therapeutic options other than lung transplantation are scarce when a fibrotic phase has been reached. One severe complication is the emergence of pulmonary hypertension that has been related to chronic hypoxia. A few papers describe its morphological characteristics focusing on arterial lesions. Otherwise, BRAF mutations have been recently described in systemic Langerhans cell histiocytosis and only one paper with five cases has been published on PLCH. Methods: We have revised morphological changes associated with pulmonary vasculature and the presence of Langerhans cells by routine and immunohistochemical methods (S100 protein, CD1a and Langerin) in 22 PLCH cases. We have used real time PCR to detect BRAF mutations in Langerhans cells using manual macrodisection in paraffin embedded tissue. Results: Six out of 22 patients (27%) showed some grade of capillary haemangiomatosis-like changes. Aggregates of Langerhans cells were located in interlobular septa in those cases. Two BRAF mutated cases were found, both of them in cellular/mixed lesions. Conclusion: We present six patients with capillary haemangiomatosis-like changes with infrequent located Langerhans cells in pulmonary Langerhans cell histiocytosis. We confirm the occurrence of BRAF mutations in this kind of disease
Beyond Tabula Rasa: Reincarnating Reinforcement Learning
Learning tabula rasa, that is without any prior knowledge, is the prevalent
workflow in reinforcement learning (RL) research. However, RL systems, when
applied to large-scale settings, rarely operate tabula rasa. Such large-scale
systems undergo multiple design or algorithmic changes during their development
cycle and use ad hoc approaches for incorporating these changes without
re-training from scratch, which would have been prohibitively expensive.
Additionally, the inefficiency of deep RL typically excludes researchers
without access to industrial-scale resources from tackling
computationally-demanding problems. To address these issues, we present
reincarnating RL as an alternative workflow, where prior computational work
(e.g., learned policies) is reused or transferred between design iterations of
an RL agent, or from one RL agent to another. As a step towards enabling
reincarnating RL from any agent to any other agent, we focus on the specific
setting of efficiently transferring an existing sub-optimal policy to a
standalone value-based RL agent. We find that existing approaches fail in this
setting and propose a simple algorithm to address their limitations. Equipped
with this algorithm, we demonstrate reincarnating RL's gains over tabula rasa
RL on Atari 2600 games, a challenging locomotion task, and the real-world
problem of navigating stratospheric balloons. Overall, this work argues for an
alternative approach to RL research, which we believe could significantly
improve real-world RL adoption and help democratize it further