Github user Yunni commented on a diff in the pull request:
https://github.com/apache/spark/pull/15874#discussion_r88128199
--- Diff: mllib/src/main/scala/org/apache/spark/ml/feature/MinHashLSH.scala
---
@@ -31,13 +31,9 @@ import org.apache.spark.sql.types.StructType
/**
* :: Experimental ::
*
- * Model produced by [[MinHash]], where multiple hash functions are
stored. Each hash function is
- * a perfect hash function:
- * `h_i(x) = (x * k_i mod prime) mod numEntries`
- * where `k_i` is the i-th coefficient, and both `x` and `k_i` are from
`Z_prime^*`
- *
- * Reference:
- * [[https://en.wikipedia.org/wiki/Perfect_hash_function Wikipedia on
Perfect Hash Function]]
+ * Model produced by [[MinHashLSH]], where multiple hash functions are
stored. Each hash function is
+ * a perfect hash function for a specific set `S` with cardinality equal
to a half of `numEntries`:
--- End diff --
You are right. Actually the correct universal hash function is (ax+b) % p %
m (https://en.wikipedia.org/wiki/Universal_hashing#Hashing_integers), which is
approximately
min-wise independent families
(http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.121.8215&rep=rep1&type=pdf)
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