User-level Differentially Private Stochastic Convex Optimization: Efficient Algorithms with Optimal Rates

We study differentially private stochastic convex optimization (DP-SCO) under user-level privacy where each user may hold multiple data items. Existing work for user-level DP-SCO either requires super-polynomial runtime or requires number of users that grows polynomially with the dimensionality of the problem. We develop new algorithms for user-level DP-SCO that obtain optimal rates, run in polynomial time, and require a number of users that grow logarithmically in the dimension. Moreover, our algorithms are the first to obtain optimal rates for non-smooth functions in polynomial time. These…Apple Machine Learning Research

Acoustic Model Fusion for End-to-end Speech Recognition

Recent advances in deep learning and automatic speech recognition (ASR) have enabled the end-to-end (E2E) ASR system and boosted its accuracy to a new level. The E2E systems implicitly model all conventional ASR components, such as the acoustic model (AM) and the language model (LM), in a single network trained on audio-text pairs. Despite this simpler system architecture, fusing a separate LM, trained exclusively on text corpora, into the E2E system has proven to be beneficial. However, the application of LM fusion presents certain drawbacks, such as its inability to address the domain…Apple Machine Learning Research

Investigating Salient Representations and Label Variance Modeling in Dimensional Speech Emotion Analysis

Representations from models such as Bidirectional Encoder Representations from Transformers (BERT) and Hidden units BERT (HuBERT) have helped to achieve state-of-the-art performance in dimensional speech emotion recognition. Both HuBERT, and BERT models generate fairly large dimensional representations, and such models were not trained with emotion recognition task in mind. Such large dimensional representations result in speech emotion models with large parameter size, resulting in both memory and computational cost complexities. In this work, we investigate the selection of representations…Apple Machine Learning Research

Co-ML: Collaborative Machine Learning Model Building for Developing Dataset Design Practices

Machine learning (ML) models are fundamentally shaped by data, and building inclusive ML systems requires significant considerations around how to design representative datasets. Yet, few novice-oriented ML modeling tools are designed to foster hands-on learning of dataset design practices, including how to design for data diversity and inspect for data quality.
To this end, we outline a set of four data design practices (DDPs) for designing inclusive ML models and share how we designed a tablet-based application called Co-ML to foster the learning of DDPs through a collbaborative ML model…Apple Machine Learning Research

One Wide Feedforward is All You Need

This paper was accepted at WMT conference at EMNLP.
The Transformer architecture has two main non-embedding components: Attention and the Feed Forward Network (FFN). Attention captures interdependencies between words regardless of their position, while the FFN non-linearly transforms each input token independently. In this work, we explore the role of FFN and find that despite, and find that despite taking up a significant fraction of the model’s parameters, it is highly redundant. Concretely, we are able to substantially reduce the number of parameters with only a modest drop in accuracy by…Apple Machine Learning Research

Bin Prediction for Better Conformal Prediction

This paper was accepted at the workshop on Regulatable ML at NeurIPS 2023.
Conformal Prediction (CP) is a method of estimating risk or uncertainty when using Machine Learning to help abide by common Risk Management regulations often seen in fields like healthcare and finance. CP for regression can be challenging, especially when the output distribution is heteroscedastic, multimodal, or skewed. Some of the issues can be addressed by estimating a distribution over the output, but in reality, such approaches can be sensitive to estimation error and yield unstable intervals. Here, we circumvent…Apple Machine Learning Research

Simulation-based Inference for Cardiovascular Models

This paper was accepted at the workshop Machine Learning and the Physical Sciences at NeurIPS 2023.
Over the past decades, hemodynamics simulators have steadily evolved and have become tools of choice for studying cardiovascular systems in-silico. This comes naturally at the cost of increasing complexity since state-of-the-art models are non-linear partial differential equations depending on many parameters. While such tools are routinely used to simulate hemodynamics given physiological parameters, solving the related inverse problems — mapping waveforms to physiological parameters — has…Apple Machine Learning Research

FastSR-NeRF: Improving NeRF Efficiency on Consumer Devices with A Simple Super-Resolution Pipeline

Super-resolution (SR) techniques have recently been proposed to upscale the outputs of neural radiance fields (NeRF) and generate high-quality images with enhanced inference speeds. However, existing NeRF+SR methods increase training overhead by using extra input features, loss functions, and/or expensive training procedures such as knowledge distillation. In this paper, we aim to leverage SR for efficiency gains without costly training or architectural changes. Specifically, we build a simple NeRF+SR pipeline that directly combines existing modules, and we propose a lightweight augmentation…Apple Machine Learning Research

Unbalanced Low-Rank Optimal Transport Solvers

Two salient limitations have long hindered the relevance of optimal transport methods to machine learning. First, the computational cost of standard sample-based solvers (when used on batches of samples) is prohibitive. Second, the mass conservation constraint makes OT solvers too rigid in practice: because they must match textit{all} points from both measures, their output can be heavily influenced by outliers. A flurry of recent works has addressed these computational and modeling limitations. Still it has resulted in two separate strains of methods: While the computational outlook was…Apple Machine Learning Research

Large-scale Training of Foundation Models for Wearable Biosignals

Tracking biosignals is crucial for monitoring wellness and preempting the development of severe medical conditions. Today, wearable devices can conveniently record various biosignals, creating the opportunity to monitor health status without disruption to one’s daily routine. Despite the widespread use of wearable devices and existing digital biomarkers, the absence of curated data with annotated medical labels hinders the development of new biomarkers to measure common health conditions. In fact, medical datasets are usually small in comparison to other domains, which is an obstacle for…Apple Machine Learning Research