the-algorithm/src/scala/com/twitter/simclusters_v2/common/clustering/SimilarityFunctions.scala

package com.twitter.simclusters_v2.common.clustering

import com.twitter.simclusters_v2.common.SimClustersEmbedding

/**
 * SimilarityFunctions provide commonly used similarity functions that this clustering library needs.
 */
object SimilarityFunctions {
  def simClustersCosineSimilarity: (SimClustersEmbedding, SimClustersEmbedding) => Double =
    (e1, e2) => e1.cosineSimilarity(e2)

  def simClustersMatchingLargestDimension: (
    SimClustersEmbedding,
    SimClustersEmbedding
  ) => Double = (e1, e2) => {
    val doesMatchLargestDimension: Boolean = e1
      .topClusterIds(1)
      .exists { id1 =>
        e2.topClusterIds(1).contains(id1)
      }

    if (doesMatchLargestDimension) 1.0
    else 0.0
  }

  def simClustersFuzzyJaccardSimilarity: (
    SimClustersEmbedding,
    SimClustersEmbedding
  ) => Double = (e1, e2) => {
    e1.fuzzyJaccardSimilarity(e2)
  }
}