Olivia Hsu

Erik Hellsten, Artur Souza, Johannes Lenfers et al. · stanford

We introduce the Bayesian Compiler Optimization framework (BaCO), a general purpose autotuner for modern compilers targeting CPUs, GPUs, and FPGAs. BaCO provides the flexibility needed to handle the requirements of modern autotuning tasks. Particularly, it deals with permutation, ordered, and continuous parameter types along with both known and unknown parameter constraints. To reason about these parameter types and efficiently deliver high-quality code, BaCO uses Bayesian optimiza tion algorithms specialized towards the autotuning domain. We demonstrate BaCO's effectiveness on three modern compiler systems: TACO, RISE & ELEVATE, and HPVM2FPGA for CPUs, GPUs, and FPGAs respectively. For these domains, BaCO outperforms current state-of-the-art autotuners by delivering on average 1.36x-1.56x faster code with a tiny search budget, and BaCO is able to reach expert-level performance 2.9x-3.9x faster.

Gina Sohn, Genghan Zhang, Konstantin Hossfeld et al.

Dynamic behaviors are becoming prevalent in many tensor applications. In machine learning, for example, the input tensors are dynamically shaped or ragged, and data-dependent control flow is widely used in many models. However, the limited expressiveness of prior programming abstractions for spatial dataflow accelerators forces the dynamic behaviors to be implemented statically or lacks the visibility for performance-critical decisions. To address these challenges, we present the Streaming Tensor Program (STeP), a new streaming abstraction that enables dynamic tensor workloads to run efficiently on spatial dataflow accelerators. STeP introduces flexible routing operators, an explicit memory hierarchy, and symbolic shape semantics that expose dynamic data rates and tensor dimensions. These capabilities unlock new optimizations-dynamic tiling, dynamic parallelization, and configuration time-multiplexing-that adapt to dynamic behaviors while preserving dataflow efficiency. Using a cycle-approximate simulator on representative LLM layers with real-world traces, dynamic tiling reduces on-chip memory requirement by 2.18x, dynamic parallelization improves latency by 1.5x, and configuration time-multiplexing improves compute utilization by 2.57x over implementations available in prior abstractions.

Genghan Zhang, Weixin Liang, Olivia Hsu et al. · stanford

ML libraries, often written in architecture-specific programming languages (ASPLs) that target domain-specific architectures, are key to efficient ML systems. However, writing these high-performance ML libraries is challenging because it requires expert knowledge of ML algorithms and the ASPL. Large language models (LLMs), on the other hand, have shown general coding capabilities. However, challenges remain when using LLMs for generating ML libraries using ASPLs because 1) this task is complicated even for experienced human programmers and 2) there are limited code examples because of the esoteric and evolving nature of ASPLs. Therefore, LLMs need complex reasoning with limited data in order to complete this task. To address these challenges, we introduce an adaptive self-improvement agentic system. In order to evaluate the effectiveness of our system, we construct a benchmark of a typical ML library and generate ASPL code with both open and closed-source LLMs on this benchmark. Our results show improvements of up to $3.9\times$ over a baseline single LLM.

Marco Siracusa, Olivia Hsu, Victor Soria-Pardos et al.

Irregular embedding lookups are a critical bottleneck in recommender models, sparse large language models, and graph learning models. In this paper, we first demonstrate that, by offloading these lookups to specialized access units, Decoupled Access-Execute (DAE) processors achieve 2.6$\times$ higher performance and 6.4$\times$ higher performance/watt than GPUs on end-to-end models. Then, we propose the Ember compiler for automatically generating optimized DAE code from PyTorch and TensorFlow. Conversely from other DAE compilers, Ember features multiple intermediate representations specifically designed for different optimization levels. In this way, Ember can implement all optimizations to match the performance of hand-written code, unlocking the full potential of DAE architectures at scale.