Github user sethah commented on a diff in the pull request:
https://github.com/apache/spark/pull/15413#discussion_r85188183
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/clustering/GaussianMixture.scala ---
@@ -350,6 +458,145 @@ object GaussianMixture extends
DefaultParamsReadable[GaussianMixture] {
@Since("2.0.0")
override def load(path: String): GaussianMixture = super.load(path)
+
+ /**
+ * Heuristic to distribute the computation of the
[[MultivariateGaussian]]s, approximately when
+ * d > 25 except for when k is very small.
+ *
+ * @param k Number of topics
+ * @param d Number of features
+ */
+ private[clustering] def shouldDistributeGaussians(k: Int, d: Int):
Boolean = {
+ ((k - 1.0) / k) * d > 25
+ }
+
+ /**
+ * Unpack upper triangular part of a symmetric matrix.
--- End diff --
"Convert an n * (n + 1) / 2 dimension array representing the upper
triangular part of a matrix into an n * n array representing the full symmetric
matrix". I think that's more explicit about what is happening. Also very minor
nit, can we call the array `triangularValues` instead? `triangular` sounds like
it should be a boolean to me.
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