replace 10MB breeze jar with simple gaussian implementation

build.sbt

@@ -273,7 +273,7 @@ lazy val importer = module("importer",
 
 lazy val insight = module("insight",
   Seq(common, game, user, analyse, relation, pref, socket, round, security),
-  Seq(scalatags, breeze) ++ reactivemongo.bundle
+  Seq(scalatags, apacheMath) ++ reactivemongo.bundle
 )
 
 lazy val tutor = module("tutor",

modules/insight/src/main/Gaussian.scala

@@ -0,0 +1,30 @@
+package lila.insight
+
+import math.{ Pi, log1p }
+import org.apache.commons.math3.special.Erf.{ erf, erfInv }
+import scala.math.{ sqrt, log }
+
+/** Represents a Gaussian distribution over a single real variable. */
+final class Gaussian(mu: Double, sigma: Double):
+
+  def draw(): Double = mu + sigma * ornicar.scalalib.ThreadLocalRandom.nextGaussian()
+
+  /** Computes the inverse cdf of the p-value for this gaussian.
+    *
+    * @param p:
+    *   a probability in [0,1]
+    * @return
+    *   x s.t. cdf(x) = numYes
+    */
+  def inverseCdf(p: Double): Double = {
+    require(p >= 0)
+    require(p <= 1)
+
+    mu + sigma * sqrt2 * erfInv(2 * p - 1)
+  }
+
+  /** Computes the cumulative density function of the value x.
+    */
+  def cdf(x: Double): Double = .5 * (1 + erf((x - mu) / (sqrt2 * sigma)))
+
+  private val sqrt2 = math.sqrt(2.0)

modules/insight/src/main/Question.scala

@@ -13,16 +13,14 @@ case class Question[X](
 
 object Question:
 
-  private val peerDistribution = {
+  private val peerDistribution =
     // > db.insight.estimatedDocumentCount()
     // 277226337
     // > db.insight.aggregate([{$sample:{size:10000000}},{$project:{_id:0,mr:1}},{$match:{mr:{$exists:1}}},{$group:{_id:null,ratings:{$avg:'$mr'}}}])
     // { "_id" : null, "ratings" : 1878.1484907826184 }
     // > db.insight.aggregate([{$sample:{size:10000000}},{$project:{_id:0,mr:1}},{$match:{mr:{$exists:1}}},{$group:{_id:null,ratings:{$stdDevSamp:'$mr'}}}])
     // { "_id" : null, "ratings" : 357.42969844387625 }
-    import breeze.stats.distributions.*
-    Gaussian(1878d, 357d)(using Rand)
-  }
+    Gaussian(1878d, 357d)
 
   case class Peers(rating: MeanRating):
     lazy val ratingRange: Range =

project/Dependencies.scala

@@ -29,11 +29,11 @@ object Dependencies {
   val lettuce     = "io.lettuce"                    % "lettuce-core"                    % "6.2.4.RELEASE"
   val nettyTransport =
     "io.netty" % s"netty-transport-native-$notifier" % "4.1.91.Final" classifier s"$os-$arch"
-  val munit       = "org.scalameta"              %% "munit"        % "1.0.0-M7" % Test
-  val uaparser    = "org.uaparser"               %% "uap-scala"    % "0.14.0"
-  val apacheText  = "org.apache.commons"          % "commons-text" % "1.10.0"
-  val bloomFilter = "com.github.alexandrnikitin" %% "bloom-filter" % "0.13.1_lila-1"
-  val breeze      = "org.scalanlp"               %% "breeze"       % "2.1.0"
+  val munit       = "org.scalameta"              %% "munit"         % "1.0.0-M7" % Test
+  val uaparser    = "org.uaparser"               %% "uap-scala"     % "0.14.0"
+  val apacheText  = "org.apache.commons"          % "commons-text"  % "1.10.0"
+  val apacheMath  = "org.apache.commons"          % "commons-math3" % "3.6.1"
+  val bloomFilter = "com.github.alexandrnikitin" %% "bloom-filter"  % "0.13.1_lila-1"
 
   object tests {
     val bundle = Seq(munit)