Automated CNN pipeline generation for heterogeneous architectures

Heterogeneity is a vital feature in emerging processor chip designing. Asymmetric multicore-clusters such as high-performance cluster and power efficient cluster are common in modern edge devices. One example is Intel\u27s Alder Lake featuring Golden Cove high-performance cores and Gracemont power-efficient cores. Chiplet-based technology allows organization of multi cores in form of multi-chip-modules, thus housing large number of cores in a processor. Interposer based packaging has enabled embedding High Bandwidth Memory (HBM) on chip and reduced transmission latency and energy consumption of chiplet-chiplet interconnect.\ua0For Instance Intel\u27s XeHPC Ponte Vecchio package integrates multi-chip GPU organization along with HBM modules.Since new devices feature heterogeneity at the level of cores, memory and on-chip interconnect, it has become important to steer optimization at application level in order to leverage the new heterogeneous, high-performing and power-efficient features of underlying computing platforms. An important high-performance application paradigm is Convolution Neural Networks (CNN). CNNs are widely used in many practical applications. The pipelined parallel implementation of CNN is favored for inference on edge devices. In this Licentiate thesis we present a novel scheme for automatic scheduling of CNN pipelines on heterogeneous devices. A pipeline schedule is a configuration that provides information on depth of pipeline, grouping of CNN layers into pipeline stages and mapping of pipeline stages onto computing units. We utilize simple compile-time hints which consists of workload information of individual CNN layers and performance hints of computing units.The proposed approach provides near optimal solution for a throughput maximizing pipeline. We model the problem as a design space exploration technique. We developed a time-efficient design space navigation through heuristics extracted from the knowledge of CNN structure and underlying computing platform. The proposed search scheme converges faster and utilizes real-time performance measurements as fitness values. The results demonstrate that the proposed scheme converges faster and can scale when used with larger networks and computing platforms. Since the scheme utilizes online performance measurements, one of the challenges is to avoid expensive configurations during online tuning. The results demonstrate that on average, ~80\% of the tested configurations are sub-optimal solutions.Another challenge is to reduce convergence time. The experiments show that proposed approach is 35x faster than stochastic optimization algorithms. Since the design space is large and complex, We show that the proposed scheme explores only ~0.1% of the total design space in case of large CNNs (having 50+ layers) and results in near-optimal solution

ODIN: Overcoming Dynamic Interference in\ua0iNference Pipelines

As an increasing number of businesses becomes powered by machine-learning, inference becomes a core operation, with a growing trend to be offered as a service. In this context, the inference task must meet certain service-level objectives (SLOs), such as high throughput and low latency. However, these targets can be compromised by interference caused by long- or short-lived co-located tasks. Prior works focus on the generic problem of co-scheduling to mitigate the effect of interference on the performance-critical task. In this work, we focus on inference pipelines and propose ODIN, a technique to mitigate the effect of interference on the performance of the inference task, based on the online scheduling of the pipeline stages. Our technique detects interference online and automatically re-balances the pipeline stages to mitigate the performance degradation of the inference task. We demonstrate that ODIN successfully mitigates the effect of interference, sustaining the latency and throughput of CNN inference, and outperforms the least-loaded scheduling (LLS), a common technique for interference mitigation. Additionally, it is effective in maintaining service-level objectives for inference, and it is scalable to large network models executing on multiple processing elements

An online guided tuning approach to run CNN pipelines on edge devices

Modern edge and mobile devices are equipped with powerful computing resources. These are often organized as heterogeneous multi-cores, featuring performance-asymmetric core clusters. This raises the question on how to effectively execute the inference pass of convolutional neural networks (CNN) on such devices. Existing CNN implementations on edge devices leverage offline profiling data to determine a better schedule for CNN applications. This approach requires a time consuming phase of generating a performance profile for each type of representative kernel on various core configurations available on the device, coupled with a search space exploration. We propose an online tuning technique which utilizes compile time hints and online profiling data to generate high throughput CNN pipelines. We explore core heterogeneity and compatible core-layer configurations through an online guided search. Unlike exhaustive search, we adopt an evolutionary approach with a guided starting point in order to find the solution. We show that by pruning and navigating through the complex search space using compile time hints, 79% of the tested configurations turn out to be near-optimal candidates for a throughput maximizing pipeline on NVIDIA Jetson TX2 platform

Shisha: Online Scheduling of\ua0CNN Pipelines on\ua0Heterogeneous Architectures

Many modern multicore processors integrate asymmetric core clusters. With the trend towards Multi-Chip-Modules (MCMs) and interposer-based packaging technologies, platforms will feature heterogeneity at the level of cores, memory subsystem and the interconnect. Due to their potential high memory throughput and energy efficient core modules, these platforms are prominent targets for emerging machine learning applications, such as Convolutional Neural Networks (CNNs). To exploit and adapt to the diversity of modern heterogeneous chips, CNNs need to be quickly optimized in terms of scheduling and workload distribution among computing resources. To address this we propose Shisha, an online approach to generate and schedule parallel CNN pipelines on heterogeneous MCM-based architectures. Shisha targets heterogeneity in compute performance and memory bandwidth and tunes the pipeline schedule through a fast online exploration technique. We compare Shisha with Simulated Annealing, Hill Climbing and Pipe-Search. On average, the convergence time is improved by ∼ 35 7 in Shisha compared to other exploration algorithms. Despite the quick exploration, Shisha’s solution is often better than that of other heuristic exploration algorithms

LEGaTO: Low-Energy, Secure, and Resilient Toolset for Heterogeneous Computing

The LEGaTO project leverages task-based programming models to provide a software ecosystem for Made in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC, balanced with the security and resilience challenges. LEGaTO is an ongoing three-year EU H2020 project started in December 2017