Github user sethah commented on a diff in the pull request: https://github.com/apache/spark/pull/15874#discussion_r87906133 --- 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 -- I'm not following exactly why the cardinality of `S` is _half_ of `numEntries`. Actually, why is threshold for feature dimensionality `prime / 2` ?
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