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author | Sean Owen <sowen@cloudera.com> | 2016-12-07 17:34:45 +0800 |
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committer | Sean Owen <sowen@cloudera.com> | 2016-12-07 17:34:45 +0800 |
commit | 79f5f281bb69cb2de9f64006180abd753e8ae427 (patch) | |
tree | a722ebc403cc4655e96e48b9e3de7502e04271a0 /sql | |
parent | b8280271396eb74638da6546d76bbb2d06c7011b (diff) | |
download | spark-79f5f281bb69cb2de9f64006180abd753e8ae427.tar.gz spark-79f5f281bb69cb2de9f64006180abd753e8ae427.tar.bz2 spark-79f5f281bb69cb2de9f64006180abd753e8ae427.zip |
[SPARK-18678][ML] Skewed reservoir sampling in SamplingUtils
## What changes were proposed in this pull request?
Fix reservoir sampling bias for small k. An off-by-one error meant that the probability of replacement was slightly too high -- k/(l-1) after l element instead of k/l, which matters for small k.
## How was this patch tested?
Existing test plus new test case.
Author: Sean Owen <sowen@cloudera.com>
Closes #16129 from srowen/SPARK-18678.
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