Computing the Expected Makespan of Task Graphs in the Presence of Silent Errors

TitleComputing the Expected Makespan of Task Graphs in the Presence of Silent Errors
Publication TypeJournal Article
Year of Publication2018
AuthorsCasanova, H., J. Herrmann, and Y. Robert
JournalParallel Computing
Date Published2018-07
KeywordsExpected makespan, fault-tolerance, scheduling, Scientific workflows, silent errors, Task graphs

Applications structured as Directed Acyclic Graphs (DAGs) of tasks occur in many domains, including popular scientific workflows. DAG scheduling has thus received an enormous amount of attention. Many of the popular DAG scheduling heuristics make scheduling deci- sions based on path lengths. At large scale compute platforms are subject to various types of failures with non-negligible probabilities of occurrence. Failures that have recently re- ceived increased attention are “silent errors,” which cause data corruption. Tolerating silent errors is done by checking the validity of computed results and possibly re-executing a task from scratch. The execution time of a task then becomes a random variable, and so do path lengths in a DAG. Unfortunately, computing the expected makespan of a DAG (and equivalently computing expected path lengths in a DAG) is a computationally dif- ficult problem. Consequently, designing effective scheduling heuristics in this context is challenging. In this work, we propose an algorithm that computes a first order approxi- mation of the expected makespan of a DAG when tasks are subject to silent errors. We find that our proposed approximation outperforms previously proposed approaches both in terms of approximation error and of speed.

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