I am broadly interested in Probabilistic Machine Learning, Perception and Geometry,
with a focus on Conditional Generative Models, Hierarchical Variational Inference,
Few-Shot Generation, Transfer Learning, and Diffusion Models.
I am interested in the generalization and adaptation capacities of hierarchical generative models.
Large generative models trained on millions of data points exhibit emergent adaptation properties like in-context learning, being able to solve novel tasks given a handful of samples.
However, such adaptation properties emerge only with scale, being absent for middle-size models trained on small datasets,
a typical scenario in engineering design and scientific discovery, where data collection is expensive and computational constraints are present.
My research goal is to bridge the gap in adaptation capabilities between large and middle-size generative models.
Leveraging the tools of hierarchical inference and using the training dataset in such a way as to encourage adaptation at inference time,
we can learn expressive families of conditional generative processes and perform few-shot generation and transfer learning in the small data regime.
Few-Shot Diffusion Models
Denoising diffusion probabilistic models (DDPM) are powerful hierarchical latent variable models with remarkable sample generation quality and training stability.
These properties can be attributed to parameter sharing in the generative hierarchy, as well as a parameter-free diffusion-based inference procedure.
In this paper, we present Few-Shot Diffusion Models (FSDM), a framework for few-shot generation leveraging conditional DDPMs.
FSDMs are trained to adapt the generative process conditioned on a small set of images from a given class by aggregating image patch information using a set-based Vision Transformer (ViT).
At test time, the model is able to generate samples from previously unseen classes conditioned on as few as 5 samples from that class.
We empirically show that FSDM can perform few-shot generation and transfer to new datasets taking full advantage of the conditional DDPM.
SCHA-VAE: Hierarchical Context Aggregation for
International Conference on Machine Learning, ICML, 2022
A few-shot generative model should be able to generate data from a novel distribution by only observing a limited set of examples.
In few-shot learning the model is trained on data from many sets from distributions sharing some underlying properties such
as sets of characters from different alphabets or objects from different categories.
We extend current latent variable models for sets to a fully hierarchical approach with an attention-based point to
set-level aggregation and call our method SCHA-VAE for Set-Context-Hierarchical-Aggregation Variational Autoencoder.
We explore likelihood-based model comparison, iterative data sampling, and adaptation-free out-of-distribution generalization.
Our results show that the hierarchical formulation better captures the intrinsic variability within the sets in the small data regime.
This work generalizes deep latent variable approaches to few-shot learning, taking a step toward large-scale few-shot generation with
a formulation that readily works with current state-of-the-art deep generative models.
Just Mix Once: Worst-group Generalization by Group
Under-review, 2022 - also Distribution Shifts Workshop, NeurIPS, 2021
Advances in deep learning theory have revealed how average generalization relies on superficial patterns in data.
The consequences are brittle models with poor performance with shift in group distribution at test time.
When group annotation is available, we can use robust optimization tools to tackle the problem.
However, identification and annotation are time-consuming, especially on large datasets.
A recent line of work leverages self-supervision and oversampling to improve generalization on minority groups
without group annotation. We propose to unify and generalize these approaches using a class-conditional variant
of mixup tailored for worst-group generalization. Our approach, Just Mix Once (JM1),
interpolates samples during learning, augmenting the training distribution with a continuous mixture of groups.
JM1 is domain agnostic and computationally efficient, can be used with any level of group annotation,
and performs on par or better than the state-of-the-art on worst-group generalization.
Additionally, we provide a simple explanation of why JM1 works.
Hierarchical Few-Shot Generative Models
Meta-Learning Workshop, NeurIPS, 2021
A few-shot generative model should be able to generate data from a distribution
by only observing a limited set of examples. In few-shot learning the model is
trained on data from many sets from different distributions sharing some underlying
properties such as sets of characters from different alphabets or sets of images
of different type objects. We study a latent variables approach that extends the
Neural Statistician to a fully hierarchical approach with an attention-based
point to set-level aggregation. We extend the previous work to iterative data sampling,
likelihood-based model comparison, and adaptation-free out of distribution
generalization. Our results show that the hierarchical formulation better captures
the intrinsic variability within the sets in the small data regime. With this work
we generalize deep latent variable approaches to few-shot learning, taking a step
towards large-scale few-shot generation with a formulation that readily can work
with current state-of-the-art deep generative models.
Transformation-aware Variational Autoencoder
Technical Report, 2020
We extend the framework of variational autoencoders to represent transformations
explicitly in the latent space. This is achieved in the form of a generative model
structured such that the group of transformations
that act in the input space is instead represented by latent variables
which are linear operators that only act in the latent space.
In the family of hierarchical graphical models that emerges,
the latent space is populated by higher order objects which are inferred
jointly with the latent representations they act on.
Real-time Classification from Short Event-Camera Streams using Input-filtering Neural ODEs
Interpretable Inductive Biases
and Physically Structured Learning Workshop, NeurIPS, 2020
Event-based cameras are novel, efficient sensors inspired by the human vision system,
generating an asynchronous, pixel-wise stream of data.
Learning from such data is generally performed through heavy preprocessing and event integration into images.
This requires buffering of possibly long sequences and can limit the response time of the inference system.
In this work, we instead propose to directly use events from a DVS camera,
a stream of intensity changes and their spatial coordinates.
This sequence is used as the input for a novel asynchronous RNN-like architecture,
the Input-filtering Neural ODEs.
No Representation without Transformation
Bayesian Deep Learning and Perception as Generative Reasoning Workshops, NeurIPS , 2019
We propose to extend Latent Variable Models with a simple idea:
learn to encode not only samples but also transformations of such samples.
This means that the latent space is not only populated by embeddings
but also by higher order objects that map between these embeddings.
We show how a hierarchical graphical model can be utilized to enforce
desirable algebraic properties of such latent mappings.
Learning Common Representation from RGB and Depth Images
Multimodal Learning and Applications Workshop, CVPR, 2019
We propose a new deep learning architecture for the tasks of semantic segmentation
and depth prediction from RGB-D images.
We revise the state of art based on the RGB and depth feature fusion,
where both modalities are assumed to be available at train and test time.
We propose a new architecture where the feature fusion is replaced with a common deep representation.
Combined with an encoder-decoder type of the network, the architecture can jointly learn models
for semantic segmentation and depth estimation based on their common representation.
Learning Common Representation for Scene Understanding
Master's Thesis, Data Science, Sapienza University of Rome, 2018
Bubble Dynamics in Turbulent Shear Flows
Master's Thesis, Mechanical Engineering, Sapienza University of Rome, 2016