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Posted to common-issues@hadoop.apache.org by "Luke Lu (JIRA)" <ji...@apache.org> on 2014/09/29 20:47:34 UTC
[jira] [Created] (HADOOP-11152) Better random number generator
Luke Lu created HADOOP-11152:
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Summary: Better random number generator
Key: HADOOP-11152
URL: https://issues.apache.org/jira/browse/HADOOP-11152
Project: Hadoop Common
Issue Type: Improvement
Reporter: Luke Lu
HDFS-7122 showed that naive ThreadLocal usage of simple LCG based j.u.Random creates unacceptable distribution of random numbers for block placement. Similarly, ThreadLocalRandom in java 7 (same static thread local with synchronized methods overridden) has the same problem.
"Better" is defined as better quality and faster than j.u.Random (which is already much faster (20x) than SecureRandom).
People (e.g. Numerical Recipes) have shown that by combining LCG and XORShift we can have a better fast RNG. It'd be worthwhile to investigate a thread local version of these "better" RNG.
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