MLSys 2021 Awards


Award Date Paper
Outstanding Paper Award
Tue 17:00 A Deep Learning Based Cost Model for Automatic Code Optimization

Enabling compilers to automatically optimize code has been a longstanding goal for the compiler community. Efficiently solving this problem requires using precise cost models. These models predict whether applying a sequence of code transformations reduces the execution time of the program. Building an analytical cost model to do so is hard in modern x86 architectures due to the complexity of the microarchitecture. In this paper, we present a novel deep learning based cost model for automatic code optimization. This model was integrated in a search method and implemented in the Tiramisu compiler to select the best code transformations. The input of the proposed model is a set of simple features representing the unoptimized code and a sequence of code transformations. The model predicts the speedup expected when the code transformations are applied. Unlike previous models, the proposed one works on full programs and does not rely on any heavy feature engineering. The proposed model has only 16% of mean absolute percentage error in predicting speedups on full programs. The proposed model enables Tiramisu to automatically find code transformations that match or are better than state-of-the-art compilers without requiring the same level of heavy feature engineering required by those compilers

Outstanding Paper Award
Tue 17:00 Cortex: A Compiler for Recursive Deep Learning Models

Optimizing deep learning models is generally performed in two steps: (i) high-level graph optimizations such as kernel fusion and (ii) low level kernel optimizations such as those found in vendor libraries. This approach often leaves significant performance on the table, especially for the case of recursive deep learning models. In this paper, we present Cortex, a compiler-based approach to generate highly-efficient code for recursive models for low latency inference. Our compiler approach and low reliance on vendor libraries enables us to perform end-to-end optimizations, leading to up to 14X lower inference latencies over past work, across different backends.

Outstanding Paper Award
Tue 17:00 Data Movement Is All You Need: A Case Study on Optimizing Transformers

Transformers are one of the most important machine learning workloads today. Training one is a very compute-intensive task, often taking days or weeks, and significant attention has been given to optimizing transformers. Despite this, existing implementations do not efficiently utilize GPUs. We find that data movement is the key bottleneck when training. Due to Amdahl's Law and massive improvements in compute performance, training has now become memory-bound. Further, existing frameworks use suboptimal data layouts. Using these insights, we present a recipe for globally optimizing data movement in transformers. We reduce data movement by up to 22.91% and overall achieve a 1.30x performance improvement over state-of-the-art frameworks when training a BERT encoder layer and 1.19x for the entire BERT. Our approach is applicable more broadly to optimizing deep neural networks, and offers insight into how to tackle emerging performance bottlenecks.

Outstanding Paper Award
Tue 17:00 In-network Aggregation for Shared Machine Learning Clusters

We present PANAMA, a network architecture for machine learning (ML) workloads on shared clusters where a variety of training jobs co-exist.PANAMA consists of two key components: (i) an efficient in-network hardware accelerator designed to accelerate large data-parallel training transfers; and (ii) a lightweight congestion control protocol to enable fair sharing of network resources across different flows. Our congestion control protocol exploits the unique communication pattern in training to ensure large in-network aggregation transfers do not negatively impact short latency-sensitive flows. To evaluate the feasibility of PANAMA, we build an FPGA-based prototype with 10 Gbps transceivers and show that our hardware datapath achieves line-rate aggregation. Our large-scale simulations demonstrate that PANAMA improves the mean and 99%-tile completion time of latency-sensitive short flows by a factor of 2–4.5 while reducing the average training time of large jobs by a factor of 1.25.

Outstanding Paper Award
Tue 17:00 TT-Rec: Tensor Train Compression for Deep Learning Recommendation Models

The memory capacity of embedding tables in deep learning recommendation models (DLRMs) is increasing dramatically from tens of GBs to TBs across the industry. Given the fast growth in DLRMs, novel solutions are urgently needed in order to enable DLRM innovations. At the same time, this must be done in a fast and efficient way without having to exponentially increase infrastructure capacity demands. In this paper, we demonstrate the promising potential of Tensor Train decomposition for DLRMs (TT-Rec), an important yet under-investigated context. We design and implement optimized kernels (TT-EmbeddingBag) to evaluate the proposed TT-Rec design. TT-EmbeddingBag is 3x faster than the SOTA TT implementation. The performance of TT-Rec is further optimized with the batched matrix multiplication and caching strategies for embedding vector lookup operations. In addition, we present mathematically and empirically the effect of weight initialization distribution on DLRM accuracy and propose to initialize the tensor cores of TT-Rec following the sampled Gaussian distribution. We evaluate TT-Rec across three important design space dimensions---memory capacity, accuracy, and timing performance---by training MLPerf-DLRM with Criteo's Kaggle and Terabyte data sets. TT-Rec compresses the model size by 4x to 221x for Kaggle, with 0.03% to 0.3% loss of accuracy correspondingly. For Terabyte, our approach achieves 112x model size reduction which comes with no accuracy loss nor training time overhead as compared to the uncompressed baseline.