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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