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Jonathan Turner Eagles commented on MAPREDUCE-7208: --------------------------------------------------- [~ahussein], could you take a look at the test failures? Also, some of the checkstyle seem relevant, but others not. > Tuning TaskRuntimeEstimator > ---------------------------- > > Key: MAPREDUCE-7208 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-7208 > Project: Hadoop Map/Reduce > Issue Type: Improvement > Reporter: Ahmed Hussein > Assignee: Ahmed Hussein > Priority: Minor > Attachments: MAPREDUCE-7208.001.patch, smoothing-exponential.md > > > By default, MR uses LegacyTaskRuntimeEstimator to get an estimate of the > runtime. The estimator does not adjust dynamically to the progress rate of > the tasks. On the other hand, the existing alternative > "ExponentiallySmoothedTaskRuntimeEstimator" behavior in unpredictable. > > There are several dimensions to improve the exponential implementation: > # Exponential shooting needs a warmup period. Otherwise, the estimate will > be affected by the initial values. > # Using a single smoothing factor (Lambda) does not work well for all the > tasks. To increase the level of smoothing across the majority of tasks, we > need to give a range of flexibility to dynamically adjust the smoothing > factor based on the history of the task progress. > # Design wise, it is better to separate between the statistical model and > the MR interface. We need to have a way to evaluate estimators statistically, > without the need to run MR. For example, an estimator can be evaluated as a > black box by using a stream of raw data as input and testing the accuracy of > the generated stream of estimates. > # The exponential estimator speculates frequently and fails to detect > slowing tasks. It does not detect slowing tasks. As a result, a taskAttempt > that does not do any progress won't trigger a new speculation. > > The file [^smoothing-exponential.md] describes how Simple Exponential > smoothing factor works. > > -- This message was sent by Atlassian Jira (v8.3.4#803005) --------------------------------------------------------------------- To unsubscribe, e-mail: mapreduce-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: mapreduce-issues-h...@hadoop.apache.org