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1. Tracking Causal Order in AWS Lambda Applications

   https://doi.org/10.1109/IC2E.2018.00027  

   Lin, Wei-Tsung; Krintz, Chandra; Wolski, Rich; Zhang, Michael; Cai, Xiaogang; Li, Tongjun; Xu, Weijin (April 2018, IEEE International Conference on Cloud Engineering (IC2E))

   Serverless computing is a new cloud programming and deployment paradigm that is receiving wide-spread uptake. Serverless offerings such as Amazon Web Services (AWS) Lambda, Google Functions, and Azure Functions automatically execute simple functions uploaded by developers, in response to cloud-based event triggers. The serverless abstraction greatly simplifies integration of concurrency and parallelism into cloud applications, and enables deployment of scalable distributed systems and services at very low cost. Although a significant first step, the serverless abstraction requires tools that software engineers can use to reason about, debug, and optimize their increasingly complex, asynchronous applications. Toward this end, we investigate the design and implementation of GammaRay, a cloud service that extracts causal dependencies across functions and through cloud services, without programmer intervention. We implement GammaRay for AWS Lambda and evaluate the overheads that it introduces for serverless micro-benchmarks and applications written in Python. 

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2. Collaborative Cloud-Edge-Local Offloading for Multi-Component Applications

   Gholami, Anousheh; Baras, John S. (December 2021, Proceedings of Sixth ACM/IEEE Symposium on Edge Computing - The 2nd Workshop on Edge Computing and Communications(EdgeComm 2021))

   With the explosion of intelligent and latency-sensitive applications such as AR/VR, remote health and autonomous driving, mobile edge computing (MEC) has emerged as a promising solution to mitigate the high end-to-end latency of mobile cloud computing (MCC). However, the edge servers have significantly less computing capability compared to the resourceful central cloud. Therefore, a collaborative cloud-edge-local offloading scheme is necessary to accommodate both computationally intensive and latency-sensitive mobile applications. The coexistence of central cloud, edge servers and the mobile device (MD), forming a multi-tiered heterogeneous architecture, makes the optimal application deployment very challenging especially for multi-component applications with component dependencies. This paper addresses the problem of energy and latency efficient application offloading in a collaborative cloud-edgelocal environment. We formulate a multi-objective mixed integer linear program (MILP) with the goal of minimizing the systemwide energy consumption and application end-to-end latency. An approximation algorithm based on LP relaxation and rounding is proposed to address the time complexity. We demonstrate that our approach outperforms existing strategies in terms of application request acceptance ratio, latency and system energy consumption. 

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3. Integrating Symbolic Planning and Reinforcement Learning for Following Temporal Logic Specifications

   https://doi.org/10.1109/IJCNN55064.2022.9892304  

   Xu, Duo; Fekri, Faramarz (July 2022, 2022 International Joint Conference on Neural Networks (IJCNN))

   Teaching a deep reinforcement learning (RL) agent to follow instructions in multi-task environments is a challenging problem. We consider that user defines every task by a linear temporal logic (LTL) formula. However, some causal dependencies in complex environments may be unknown to the user in advance. Hence, when human user is specifying instructions, the robot cannot solve the tasks by simply following the given instructions. In this work, we propose a hierarchical reinforcement learning (HRL) framework in which a symbolic transition model is learned to efficiently produce high-level plans that can guide the agent efficiently solve different tasks. Specifically, the symbolic transition model is learned by inductive logic programming (ILP) to capture logic rules of state transitions. By planning over the product of the symbolic transition model and the automaton derived from the LTL formula, the agent can resolve causal dependencies and break a causally complex problem down into a sequence of simpler low-level sub-tasks. We evaluate the proposed framework on three environments in both discrete and continuous domains, showing advantages over previous representative methods. 

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4. Causal lifting and link prediction

   https://doi.org/10.1098/rspa.2023.0121  

   Cotta, Leonardo; Bevilacqua, Beatrice; Ahmed, Nesreen; Ribeiro, Bruno (August 2023, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   Existing causal models for link prediction assume an underlying set of inherent node factors—an innate characteristic defined at the node’s birth—that governs the causal evolution of links in the graph. In some causal tasks, however, link formation ispath-dependent: the outcome of link interventions depends on existing links. Unfortunately, these existing causal methods are not designed for path-dependent link formation, as the cascading functional dependencies between links (arising frompath dependence) are either unidentifiable or require an impractical number of control variables. To overcome this, we develop the first causal model capable of dealing with path dependencies in link prediction. In this work, we introduce the concept of causal lifting, an invariance in causal models of independent interest that, on graphs, allows the identification of causal link prediction queries using limited interventional data. Further, we show how structural pairwise embeddings exhibit lower bias and correctly represent the task’s causal structure, as opposed to existing node embeddings, e.g. graph neural network node embeddings and matrix factorization. Finally, we validate our theoretical findings on three scenarios for causal link prediction tasks: knowledge base completion, covariance matrix estimation and consumer-product recommendations. 

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5. Resilient Distributed Causal Memory in Client-Server Model

   https://doi.org/10.1109/PRDC47002.2019.00035  

   Tseng, Lewis Wang (December 2019, 24th IEEE Pacific Rim International Symposium on Dependable Computing)

   We study distributed causal shared memory (or key- value pairs) in an asynchronous network under crash failures. Causal memory, introduced by Ahamad et al. in the context of multi-processor environment in 1994, is an abstraction which ensures that nodes agree on the relative ordering of read and write operations that are causally related on key-value pairs. Inspired by the recent interests in geo-replicated causal storage systems (e.g., COPS, Eiger, Bolt-on), we systematically study the fault-tolerance property of the causal shared memory in the client-server model in this work. We identify that 2f + 1 servers is both necessary and sufficient to build a resilient causal memory in the presence of up to f crashed servers. We provide both the necessity proof and a new optimal algorithm that matches the bound. For evaluation, we implement our algorithm in Golang and compare the perfor- mance with state-of-the-art fault-tolerant algorithms that ensure atomicity in the Google Cloud Platform. 

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