Laptop Structure analysis has an extended historical past of creating simulators and instruments to judge and form the design of pc programs. For instance, the SimpleScalar simulator was launched within the late Nineties and allowed researchers to discover varied microarchitectural concepts. Laptop structure simulators and instruments, resembling gem5, DRAMSys, and lots of extra have performed a big position in advancing pc structure analysis. Since then, these shared assets and infrastructure have benefited trade and academia and have enabled researchers to systematically construct on one another’s work, resulting in important advances within the subject.
Nonetheless, pc structure analysis is evolving, with trade and academia turning in direction of machine studying (ML) optimization to fulfill stringent domain-specific necessities, resembling ML for pc structure, ML for TinyML acceleration, DNN accelerator datapath optimization, reminiscence controllers, energy consumption, safety, and privateness. Though prior work has demonstrated the advantages of ML in design optimization, the shortage of sturdy, reproducible baselines hinders honest and goal comparability throughout totally different strategies and poses a number of challenges to their deployment. To make sure regular progress, it’s crucial to know and deal with these challenges collectively.
To alleviate these challenges, in “ArchGym: An Open-Supply Gymnasium for Machine Studying Assisted Structure Design”, accepted at ISCA 2023, we launched ArchGym, which incorporates a wide range of pc structure simulators and ML algorithms. Enabled by ArchGym, our outcomes point out that with a sufficiently giant variety of samples, any of a various assortment of ML algorithms are able to find the optimum set of structure design parameters for every goal downside; nobody answer is essentially higher than one other. These outcomes additional point out that choosing the optimum hyperparameters for a given ML algorithm is important for locating the optimum structure design, however selecting them is non-trivial. We launch the code and dataset throughout a number of pc structure simulations and ML algorithms.
Challenges in ML-assisted structure analysis
ML-assisted structure analysis poses a number of challenges, together with:
- For a selected ML-assisted pc structure downside (e.g., discovering an optimum answer for a DRAM controller) there isn’t any systematic option to determine optimum ML algorithms or hyperparameters (e.g., studying charge, warm-up steps, and many others.). There’s a wider vary of ML and heuristic strategies, from random stroll to reinforcement studying (RL), that may be employed for design house exploration (DSE). Whereas these strategies have proven noticeable efficiency enchancment over their selection of baselines, it isn’t evident whether or not the enhancements are due to the selection of optimization algorithms or hyperparameters.
Thus, to make sure reproducibility and facilitate widespread adoption of ML-aided structure DSE, it’s needed to stipulate a scientific benchmarking methodology. - Whereas pc structure simulators have been the spine of architectural improvements, there may be an rising want to deal with the trade-offs between accuracy, pace, and price in structure exploration. The accuracy and pace of efficiency estimation broadly varies from one simulator to a different, relying on the underlying modeling particulars (e.g., cycle–correct vs. ML–primarily based proxy fashions). Whereas analytical or ML-based proxy fashions are nimble by advantage of discarding low-level particulars, they often undergo from excessive prediction error. Additionally, because of industrial licensing, there might be strict limits on the variety of runs collected from a simulator. Total, these constraints exhibit distinct efficiency vs. pattern effectivity trade-offs, affecting the selection of optimization algorithm for structure exploration.
It’s difficult to delineate the right way to systematically examine the effectiveness of assorted ML algorithms beneath these constraints. - Lastly, the panorama of ML algorithms is quickly evolving and a few ML algorithms want knowledge to be helpful. Moreover, rendering the result of DSE into significant artifacts resembling datasets is crucial for drawing insights concerning the design house.
On this quickly evolving ecosystem, it’s consequential to make sure the right way to amortize the overhead of search algorithms for structure exploration. It’s not obvious, nor systematically studied the right way to leverage exploration knowledge whereas being agnostic to the underlying search algorithm.
ArchGym design
ArchGym addresses these challenges by offering a unified framework for evaluating totally different ML-based search algorithms pretty. It includes two primary elements: 1) the ArchGym atmosphere and a couple of) the ArchGym agent. The atmosphere is an encapsulation of the structure value mannequin — which incorporates latency, throughput, space, power, and many others., to find out the computational value of operating the workload, given a set of architectural parameters — paired with the goal workload(s). The agent is an encapsulation of the ML algorithm used for the search and consists of hyperparameters and a guiding coverage. The hyperparameters are intrinsic to the algorithm for which the mannequin is to be optimized and might considerably affect efficiency. The coverage, alternatively, determines how the agent selects a parameter iteratively to optimize the goal goal.
Notably, ArchGym additionally features a standardized interface that connects these two elements, whereas additionally saving the exploration knowledge because the ArchGym Dataset. At its core, the interface entails three primary indicators: {hardware} state, {hardware} parameters, and metrics. These indicators are the naked minimal to determine a significant communication channel between the atmosphere and the agent. Utilizing these indicators, the agent observes the state of the {hardware} and suggests a set of {hardware} parameters to iteratively optimize a (user-defined) reward. The reward is a perform of {hardware} efficiency metrics, resembling efficiency, power consumption, and many others.
 |
| ArchGym includes two primary elements: the ArchGym atmosphere and the ArchGym agent. The ArchGym atmosphere encapsulates the associated fee mannequin and the agent is an abstraction of a coverage and hyperparameters. With a standardized interface that connects these two elements, ArchGym offers a unified framework for evaluating totally different ML-based search algorithms pretty whereas additionally saving the exploration knowledge because the ArchGym Dataset. |
ML algorithms might be equally favorable to fulfill user-defined goal specs
Utilizing ArchGym, we empirically display that throughout totally different optimization targets and DSE issues, at the least one set of hyperparameters exists that leads to the identical {hardware} efficiency as different ML algorithms. A poorly chosen (random choice) hyperparameter for the ML algorithm or its baseline can result in a deceptive conclusion {that a} specific household of ML algorithms is healthier than one other. We present that with ample hyperparameter tuning, totally different search algorithms, even random stroll (RW), are in a position to determine the very best reward. Nevertheless, word that discovering the suitable set of hyperparameters could require exhaustive search and even luck to make it aggressive.
 |
| With a ample variety of samples, there exists at the least one set of hyperparameters that leads to the identical efficiency throughout a variety of search algorithms. Right here the dashed line represents the utmost normalized reward. Cloud-1, cloud-2, stream, and random point out 4 totally different reminiscence traces for DRAMSys (DRAM subsystem design house exploration framework). |
Dataset building and high-fidelity proxy mannequin coaching
Making a unified interface utilizing ArchGym additionally allows the creation of datasets that can be utilized to design higher data-driven ML-based proxy structure value fashions to enhance the pace of structure simulation. To judge the advantages of datasets in constructing an ML mannequin to approximate structure value, we leverage ArchGym’s skill to log the info from every run from DRAMSys to create 4 dataset variants, every with a distinct variety of knowledge factors. For every variant, we create two classes: (a) Numerous Dataset, which represents the info collected from totally different brokers (ACO, GA, RW, and BO), and (b) ACO solely, which reveals the info collected completely from the ACO agent, each of that are launched together with ArchGym. We prepare a proxy mannequin on every dataset utilizing random forest regression with the target to foretell the latency of designs for a DRAM simulator. Our outcomes present that:
- As we enhance the dataset measurement, the common normalized root imply squared error (RMSE) barely decreases.
- Nevertheless, as we introduce variety within the dataset (e.g., accumulating knowledge from totally different brokers), we observe 9× to 42× decrease RMSE throughout totally different dataset sizes.
 |
| Numerous dataset assortment throughout totally different brokers utilizing ArchGym interface. |
 |
| The affect of a various dataset and dataset measurement on the normalized RMSE. |
The necessity for a community-driven ecosystem for ML-assisted structure analysis
Whereas, ArchGym is an preliminary effort in direction of creating an open-source ecosystem that (1) connects a broad vary of search algorithms to pc structure simulators in an unified and easy-to-extend method, (2) facilitates analysis in ML-assisted pc structure, and (3) types the scaffold to develop reproducible baselines, there are a variety of open challenges that want community-wide assist. Under we define among the open challenges in ML-assisted structure design. Addressing these challenges requires a properly coordinated effort and a neighborhood pushed ecosystem.
 |
| Key challenges in ML-assisted structure design. |
We name this ecosystem Structure 2.0. We define the important thing challenges and a imaginative and prescient for constructing an inclusive ecosystem of interdisciplinary researchers to deal with the long-standing open issues in making use of ML for pc structure analysis. In case you are keen on serving to form this ecosystem, please fill out the curiosity survey.
Conclusion
ArchGym is an open supply gymnasium for ML structure DSE and allows an standardized interface that may be readily prolonged to go well with totally different use instances. Moreover, ArchGym allows honest and reproducible comparability between totally different ML algorithms and helps to determine stronger baselines for pc structure analysis issues.
We invite the pc structure neighborhood in addition to the ML neighborhood to actively take part within the improvement of ArchGym. We imagine that the creation of a gymnasium-type atmosphere for pc structure analysis could be a big step ahead within the subject and supply a platform for researchers to make use of ML to speed up analysis and result in new and modern designs.
Acknowledgements
This blogpost is predicated on joint work with a number of co-authors at Google and Harvard College. We wish to acknowledge and spotlight Srivatsan Krishnan (Harvard) who contributed a number of concepts to this challenge in collaboration with Shvetank Prakash (Harvard), Jason Jabbour (Harvard), Ikechukwu Uchendu (Harvard), Susobhan Ghosh (Harvard), Behzad Boroujerdian (Harvard), Daniel Richins (Harvard), Devashree Tripathy (Harvard), and Thierry Thambe (Harvard). As well as, we’d additionally wish to thank James Laudon, Douglas Eck, Cliff Younger, and Aleksandra Faust for his or her assist, suggestions, and motivation for this work. We might additionally wish to thank John Guilyard for the animated determine used on this put up. Amir Yazdanbakhsh is now a Analysis Scientist at Google DeepMind and Vijay Janapa Reddi is an Affiliate Professor at Harvard.
