I conduct research at the IMT Atlantique in Brest on hardware and software implementations of signal processing and AI algorithms. I teach computer engineering and digital electronics.
My PhD thesis focused on the implementation of polar codes decoders. I proposed the fastest software implementation of the Adaptive SC List decoding algorithm to date. This implementation is integrated in the AFF3CT toolbox to which I actively contribute. I’m also part of the organisation committee of the next ISTC 2023 conference.
I currently focus on efficient hardware and software implementations of Neural Networks, aiming at low latency and energy efficiency, through multiple industrial collaborations, and as the coordinator of a JCJC ANR project, ProPruNN.
PhD in Electronics, 2018
PhD in Electronics, 2018
University of Bordeaux
MEng in Embedded Electronics, 2015
Enseirb-Matmeca, Bordeaux INP
A lot of recent progress has been made in ultra lowbit quantization, promising significant improvements in latency, memory footprint and energy consumption on edge devices. Quantization methods such as Learned Step Size Quantization can achieve model accuracy that is comparable to full-precision floating-point baselines even with subbyte quantization. However, it is extremely challenging to deploy these ultra low-bit quantized models on mainstream CPU devices because commodity SIMD (Single Instruction, Multiple Data) hardware typically supports no less than 8-bit precision. To overcome this limitation, we propose DeepGEMM, a lookup table based approach for the execution of ultra low-precision convolutional neural networks on SIMD hardware. The proposed method precomputes all possible products of weights and activations, stores them in a lookup table, and efficiently accesses them at inference time to avoid costly multiply-accumulate operations. Our 2-bit implementation outperforms corresponding 8-bit integer kernels in the QNNPACK framework by up to 1.74× on x86 platforms.
Machine Learning (ML) has become state of the art for various tasks, including classification of accelerometer data. In the world of Internet of Things (IoT), the available hardware with low-power consumption is often microcontrollers. However, one of the challenges for embedding machine learning on microcontrollers is that the available memory space is very limited, and this memory is also occupied by the rest of the software elements needed in the IoT device. The problem is then to design ML architectures that have a very low memory footprint, while maintaining a low error rate. In this paper, a methodology is proposed towards the deployment of efficient machine learning on microcontrollers. Then, such methodology is used to investigate the effect of using compression techniques mainly pruning, quantization, and coding on the memory budget. Indeed, we know that these techniques reduce the model size, but not how these techniques interoperate to reach the best accuracy to memory trade-off. A Convolutional Neural Network (CNN) and a Human Activity Recognition (HAR) application has been adopted for the validation of the study .
Introduced in the late 1980s for generalization purposes, pruning has now become a staple for compressing deep neural networks. Despite many innovations in recent decades, pruning approaches still face core issues that hinder their performance or scalability. Drawing inspiration from early work in the field, and especially the use of weight decay to achieve sparsity, we introduce Selective Weight Decay (SWD), which carries out efficient, continuous pruning throughout training. Our approach, theoretically grounded on Lagrangian smoothing, is versatile and can be applied to multiple tasks, networks, and pruning structures. We show that SWD compares favorably to state-of-the-art approaches, in terms of performance-to-parameters ratio, on the CIFAR-10, Cora, and ImageNet ILSVRC2012 datasets.
Flexibility is one mandatory aspect of channel coding in modern wireless communication systems. Among other things, the channel decoder has to support several code lengths and code rates. This need for flexibility applies to polar codes that are considered for control channels in the future 5G standard. This paper presents a new generic and flexible implementation of a software Successive Cancellation List (SCL) decoder. A large set of parameters can be fine-tuned dynamically without re-compiling the software source code: the code length, the code rate, the frozen bits set, the puncturing patterns, the cyclic redundancy check, the list size, the type of decoding algorithm, the tree-pruning strategy and the data quantization. This generic and flexible SCL decoder enables to explore tradeoffs between throughput, latency and decoding performance. Several optimizations are proposed to achieve a competitive decoding speed despite the constraints induced by the genericity and the flexibility. The resulting polar list decoder is about 4 times faster than a generic software decoder and only 2 times slower than a non-flexible unrolled decoder. Thanks to the flexibility of the decoder, the fully adaptive SCL algorithm can be easily implemented and achieves higher throughput than any other similar decoder in the literature (up to 425 Mb/s on a single processor core for N = 2048 and K = 1723 at 4.5 dB).